3a. When things don't work: Removing the Driver
Board
The majority of electronic repairs will be on the WPC Power Driver
board. To do any repairs to the driver board, it must be removed from
the game. Yes, there are seemingly an endless array of connectors that
will have to be dealt with. Fear not, all are keyed so they can't be
plugged into the wrong place (in most cases!). For confidence and
simplification, always label the connectors as they are removed. Sure,
this is probably unnecessary. But if there are any problems, the idea
that I might have incorrectly plugged the connectors can be
eliminated. It only takes a minute, and there is never any doubt about
what goes where.
Using a
mark-all "Sharpie" pen, label the sides of all the
connectors as they are removed.
|
|
Use a mark-all "Sharpie" pen to label the connectors. The side of
each connector has room for writing. After the connectors are all
marked and removed, loosen the phillips head screws that hold the
driver board in place. The screws don't have to removed all the way!
Only loosen them. The board has slots for all the screws, so the board
will lift up and out of the backbox.
Note: some connectors are "parallel". That is, they have the same
keyed pin configuration so as many as three plugs, can be switched
around. To minimize this confusion, again just mark the plugs with a
Sharpie as they are removed.
3b. When things don't work: Replacing
Components
If a bad component has been found, now comes the hard part;
replacing it! Transistors, bridge rectifiers, and most chips are not
socketed. They are soldered directly into the driver board. Care must
be taken when replacing a bad component.
Please see http://www.marvin3m.com/begin
for details on the basic electronics skills and tools needed when
replacing circuit board components.
When replacing components, the object is to subject the board to
the least amount of heat as possible. Too much heat can lift or crack
the board's traces. Too little heat and the plated-through holes can
be ripped out when removing the part. New circuit boards are too
expensive to replace. So be careful when doing this.
To remove a bad component, just CUT it off of the board, leaving as
much of its original lead(s) as possible. Then using needle nose
pliers, grab the lead in the board while heating it with the soldering
iron, and pull it out. Clean up the solder left behind with a
desoldering tool.
When replacing chips, alway install a socket. Buy good quality
sockets. Avoid "Scanbe" sockets at all costs! A good machine pin
socket is desirable.
3c. When things don't work: Checking Transistors and
Coils (stuck on coils and flashlamps)
If a coil is "stuck on" when the game is turned on, a shorted
driver transistor could be cause. If a coil does not work (and the
fuses are good!), an open driver transistor could be the cause. This
section will help diagnose this.
What do the Driver Transistors Do? Basically, a driver
transistors completes each coil's path to ground. There is power at
each coil, all the time. The driving transitor is "turned on" by the
game's software, through a TTL (Transistor to Transistor Logic) chip.
When the transistor is turned on, this completes the coil's power path
to ground, energizing the coil. Driver transistors also work the CPU
controlled lamps and flash lamps, causing a lamp to "lock on".
Sometimes these driver transistors short "on" internally. This
completes a coil or flash lamp's power path to ground permanently,
making it "stuck on", as soon as the game is turned on. Also a shorted
pre-driver transistor, or shorted TTL chip (which controls the
transistors) could be the problem (though a shorted driver transistor
is the most common cause). To fix this, the defective component (and
perhaps some other not defective, but over stressed componets) will
need to be replaced.
TIP36 and
TIP102 transistors on the driver board.
|
|
TIP102
transistors, the small 2N5401 pre-driver transistors, and the
coil diodes on the driver board.
|
|
There are basically four types of driver and pre-driver transistors
used on a WPC driver board:
- TIP36c (PNP, NTE393): used for solenoid numbers 1 to 8.
High power transistors used for more powerful solenoids (and the
flipper, on their initial "flip" on the Fliptronics board).
- TIP102 (NPN, NTE2343): used for solenoid numbers 9 to 28.
Low power solenoid and flash lamp drivers, used for most devices
(and for the flippers on their "hold" circuit on the Fliptronics
board). Numbers 9 to 16 are used for low power solenoids, number
17-20 for flash lamps, and number 21 to 28 for general purpose
solenoids or flash lamps. TIP102's are also used to switch GND on
for any particular lamp row.
- TIP107 (PNP, NTE2344): used to drive the CPU controlled
lamp (columns) on the playfield. The TIP107 switches the +18 volts
on for any particular lamp column.
- 2N5401 & MPSD52 (PNP): used as a pre-driver for the
TIP102 transistors. 2N5401, MPSD52 and NTE288 are all equivalent
transistors.
- 2N4403 (PNP, NTE159): used as a pre-driver for the
Fliptronics board.
Driver Transistor Operation. As described above, the main
driver transistor (a TIP102 or TIP36) completes the coil or flash
lamp's power path the ground, energizing it. But there are other
components involved too!
Each driver transistor has a "pre-driver" transistor. In the case
of a TIP102 (the most common WPC driver transistor), this is a smaller
2N5401/MPSD52 or 2N4403 transistor.
If the main driver transistor is a TIP36c, this is pre-driven by
both a TIP102 and a smaller 2N5401/MPSD52 or 2N4403 transistor. The
bigger TIP36c transistor is an even more robust than the TIP102, and
controls very high powered, high use coils (like the flippers).
Then before even the smaller 2N5401/MPSD52 or 2N4403 pre-driver
transistor, there is a TTL (Transistor to Transistor Logic) 74LS374
chip. This is really the first link in the chain. This is what in
affect turns on the smaller 2N5401/MPSD52 or 2N4403 pre-driver
transistor, which then turns on the TIP102 (which then turns on the
TIP36c, if used for the coil/flash lamp in question), and energized
the device.
This series of smaller to bigger transistors is done to isolate the
hi-powered coil voltage (50 volts), from the low-power logic (5 volts)
on the driver board. Also the 74LS374 chip (operating at +5 volts),
which really controls the transistors, can not directly drive a high
power TIP102 or TIP36c transistor (which is controlling 50 volts).
If ANY of these components in the chain have failed, a
coil/flashlamp can be stuck on, and will energize as soon as the game
is powered on!
I have a Stuck-on Coil (or Flashlamp), What should I
Replace? The following procedures will test the driver and
pre-driver transistors in question. If either is bad, it will need to
be replaced. When replacing either a driver or pre-driver transistor,
replace them both (or in the case of a TIP36, replace the
TIP102 and smaller 2N5401/MPSD52 or 2N4403 transistor)! A shorted
transistor will cause the other transistors in the link to be
stressed, and they should all be replaced.
Inside the front cover of the game manual is a list of each coil
used in the game. Also listed are the driving transistor(s) for each
coil. Use this chart to determine which transistors could potentially
be bad. Also use the schematics.
If after replacing the driver transistors the coil/flashlamp is
still stuck on, then replace the TTL 74LS374 logic chip. The TTL
74LS374 can also go bad (though it is not real common).
A Coil just Does Not Work - What is Wrong? Driver
transistors can go "open" too. This means all the logic prior to the
open transistor could be working fine, but the coil will not energize.
If there is power at the coil, this is something to consider (but
first see the test procedures below to make sure the coil itself is
actually OK).
Do the Transistor Test Procedures work 100%? In short,
no. But they do work about 98% of the time, and are an excellent
starting point. But yes, a transistor can test as "good", but still be
bad. The DMM test procedures test the transistors with no load. Under
load, a transistor could not work.
Testing a
transistor on the driver board. Note the DMM is set to the
diode position, and one lead is connected to the metal tab
on the TIP transistor. The two outside leads are then
tested.
|
|
Transistor Testing procedures using a DMM. If the driver
board is out of the game for some reason (like to fix the burnt GI
connector pins), test all the transistors. It only takes a moment, and
will ultimately save time. To test a transistor, a digital multi-meter
(DMM) is needed, set to the "diode" position. NOTE: testing
transistors with a DMM is not 100% fool-proof. A transistor can test
as "good" and still be bad (rare, but it does happen!).
Testing Transistors INSTALLED in the WPC driver board.
- TIP36c: Put the red lead of the DMM on the metal
tab of the transistor. Put the black lead of the DMM on each of the
two outside legs of the transistor. A reading of .4 to .6 volts
should be seen. Put the black lead on the center transistor leg
(collector) and the red lead on the metal tab, and a zero reading
should be seen. Put the black lead of the DMM on the left/top
(base) leg of the transistor. The red lead on the center transistor
leg should show .4 to .6 volts. The red lead on the right/bottom leg
should be .2 volts. Any other value, and the transistor is bad and
will need to be replaced.
- TIP102: Put the black lead of the DMM on the metal
tab of the transistor. Put the red lead of the DMM on each of the
two outside legs of the transistor. A reading of .4 to .6 volts
should be seen. Put the red lead on the center transistor leg
(collector), and a zero reading should be seen. Any other value, and
the transistor is bad and will need to be replaced.
- TIP107: Put the red lead of the DMM on the center
leg or on the metal tab of the transistor. Put the black lead of the
DMM on each of the two outside legs of the transistor. A reading of
.4 to .6 volts should be seen. Put the black lead on the center
transistor leg (collector) and the red lead on the metal tab, and a
zero reading should be seen. Any other value, and the transistor is
bad and will need to be replaced.
- 2N5401, MPSD52, 2N4403 (pre-drivers): Put the
black lead of the DMM on the center leg of the transistor
(note this transistor doesn't have a metal tab). Put the red lead of
the DMM on each of the two outside legs of the transistor. A reading
of .4 to .6 volts should be seen. Any other value, and the
transistor is bad and will need to be replaced.
Testing Transistors NOT INSTALLED. Only the TIP36c will
test slightly different out of circuit. The other transistors will
test the same as described above. All transistors are laying on the
workbench with their "face" (side with the markings) up, and metal tab
away from you. Orientation is BCE (base collector emitter), from left
to right for the TIP transistors. Orientation for the small plastic
transistors is EBC (emitter base collector) with the flat side up.
- TIP36c: Put the black lead of the DMM on the
left (base) leg of the transistor. Put the red lead of the
DMM on each of the two other legs (center and right legs) of the
transistor. A reading of .4 to .6 volts should be seen. Put the DMM
leads on the metal tab and the center transistor leg (collector),
and a zero reading should be seen. Any other value, and the
transistor is bad.
Most often transistors short when they go bad. This will usually
give a reading of zero or near zero, instead of .4 or .6 volts.
Testing Coils and Transistors; a Systematic
Approach.
If a coil is not working, the following approach is a good one to
take. It starts with the easiest test first; using the internal WPC
diagnostics. Then the tests moves to the coil itself, and goes back
towards the driver board. This makes the chain smaller, and gives a
very systematic approach to finding the problem.
Pressing
the "start game" button on the outside of the cabinet during
the Solenoid Test gives important information. In this example
(the Auto Plunger coil), it shows the coil's wire colors, the
board connectors/pins used, the fuse rating and position, and
the transistors that drive this coil. Note Q72 is a TIP36
transistor with Q60 (a TIP102) as a pre-driver, and Q56 (a
MPSD52) as a pre-driver to the TIP102.
|
|
Testing Transistors/Coils, Driver board
installed in a (near) WORKING game, using the Diagnostics
Test. If the game powers on, the WPC diagnostics can be used to
test most devices.
- Press the "Begin Test" button inside the coin door.
- Select "MAIN MENU: TESTS".
- Select "TEST MENU: SOLENOID TEST".
- Use the "+" and "-" buttons to move the test from coil to coil.
Each coil should fire. (Note the coin door interlock switch must be
held in on 1993 and later games. Otherwise the coil 50 volts will be
turned off, and the coils won't fire. Also make sure the "REPEAT"
portion of the test is used. This can be changed using the "Begin
Test" button.)
- Press the "help" button. The game's start button during the coil
test wil give more coil information including coil wire colors,
Driver board connector and pin numbers; related fuse number; Driver
board transistor and pre-driver transistor numbers.
Solenoid Doesn't Work during WPC Diagnostic Tests. If a
solenoid doesn't work from the diagnostic tests, here's what to check.
Turn the game off before doing this.
- Check all the fuses on the driver board. A non-working solenoid
could be as easy to fix as just replacing a fuse.
- Find the solenoid in question under the playfield. Make sure the
wire hasn't fallen off or become cut from the coil (a very common
problem).
- If the above is correct, make sure the winding of the coil
haven't broken off from the solder lugs. If one has broken, it can
be re-soldered. Make sure the painted enamel insulation is sanded
from the wire before re-soldering.
- Check the coil diode (for any other pinball game, this would be
the next step). The coil diode for all games (except WPC) are
attached right to the coil, with the banded side of the diode
connecting to the power side of the coil. On WPC games however,
Williams moved this diode to the power driver board for all coils
but the flipper coils. This increases reliability as the diode is
not subject to the jarring and heat a coil can produce. It also
eliminates the need for the operator to know which coil wire goes to
the banded side of the diode when replacing a coil! On a WPC game,
these coil diodes are mounted on the driver board next to the
transistor that drives each particular coil.
Quick and Dirty TIP102 Transistor Testing. There is an
easy way to test TIP102 (only) transistors. This procedure takes about
20 seconds to test all the TIP102 transistors:
- Make sure the game is off.
- Put the DMM (digital multi meter) on ohms (buzz tone).
- Put one lead on the ground strap in the backbox.
- Touch the other lead to the metal tab on the TIP102 transistors.
- If zero ohms (buzz) is indicated, the transistor is bad!
(shorted on)
The Coin Door Interlock switch. In the
middle of Twilight Zone's production in 1993, Williams added a coin
door interlock switch. This turned off the power to all the coils when
the coil door was opened (for safety reasons). On 1993 and later games
with this interlock switch, make sure the coin door is closed when
testing coils!
Failed Coin Door Interlock switch. Yes it does happen.
The coin door interlock switch can fail, or does not get pushed in
enough when the coin door is closed. This will prevent voltage from
getting to the solenoids. If none of the solenoids work, and the fuses
are good, check the coin door interlock switch for problems. A sure
sign of this is the Driver board solenoid power LED's will NOT be lit
if the coin door interlock switch is not closed! The interlock switch
opens the coil power coming from the transformer, which is way before
the power gets to the Driver board's fuses and power circuits.
Testing for Power at the Coil. Most pinball games
(including WPC) have power at each and every coil at all times. To
activate a coil, GROUND is turned on momentarily by the driving
transistor to complete the power path. Since only ground (and not
power) is turned on and off, the driving transistors have less stress
on them. With this in mind, if we artificially attach a coil to
ground, it will fire (assuming the game is turned on).
- Turn the game on and leave it in "attract" mode.
- Lift the playfield.
- Put the DMM on DC voltage (100 volts).
- Attach the black lead of the DMM to the metal side rail.
- Touch the red lead of the DMM on either lug of the coil in
question.
- A reading of 20 to 80 volts DC should be indicated. Switch the
red test lead to the other lug of the coil, and the same voltage
should be seen again. On flipper coils, test the two outside lugs of
the coil. If no voltage reading is shown, no power is getting to the
coil. On a two lug coil, if there is only voltage at one lug, the
coil winding is broken. On 1993 and newer WPC games, make sure the
coin door is closed!
- If no power is getting to the coil, a wire is probably broken
somewhere. Trace the power wire.
No Coil Power, Fuse is Good and No Broken Wires. I
recently had a problem on a Safe Cracker (WPC-95) where none of the
low power (20 volt) coils worked. It was very frustrating; the fuse
was good, and power was getting to the Driver board, but not out of
the driver board and to the coils.
It turned out that the capacitor that filters the DC voltage after
the bridge rectifier on the Driver board had a cracked solder pad.
This prevented the voltage from getting any further than it's
associated bridge rectifier (I should have known; the +20 volt LED on
the Driver board was not lit!). To fix this, I soldered jumper wires
from the bridge to the capacitor, as outlined in the below Game Resets
(Bridge Rectifiers and Diodes) section.
Testing the Coil and the Power Together. This test will
show if the power and the coil are indeed working together:
- Game is on and in "attract" mode, and the playfield lifted. On
1993 and newer WPC games, coin door is closed.
- Connect an alligator clip to the metal side rail of the game.
- Momentarily touch the other end of the alligator clip to the
GROUND lead of the coil in question. This will be the coil lug with
the single wire attached (usually brown). On flipper coils, this is
the middle lug (the power wire on most coils is usually the thicker
violet or red wire). This works on both Fliptronics and
non-Fliptronics WPC games.
- The coil should fire (if the alligator clip is accidentally
touched to the power side of the coil, the game will reset and/or
blow a fuse, as the solenoid high voltage is being shorted directly
to ground).
- If the coil does not fire, either the coil itself is bad, or the
coil's fuse is blown and power to the coil is not present.
Testing the TIP102 Transistor and Wiring to the Coil. If
the coil fires in the above test, there may be a transistor problem.
The TIP102 transistors can be tested this way. Only do this for the
TIP102 transistors! Damage can occur if this test is done on other
transistors (like TIP107 or TIP36).
- Game is on, and the "test mode" button is pressed once. On 1993
and newer WPC games, coin door is closed.
- Remove the backglass.
- Find the transistor that controls the coil in question (refer to
the manual).
- Attach an alligator clip to the grounding strap in the bottom of
the backbox.
- Momentarily touch the other lead of the alligator clip to the
metal tab on any TIP102 transistor (only works on these).
- The coil should fire.
- If the coil does not fire, and the coil did fire in the previous
test, there probably is a wiring problem. A broken wire or bad
connection at the connector would be most common. It is also
possible there is a bad transistor. Use the DMM meter and test the
transistor on the board (see Transistors
Testing Procedures for details).
The Above Tests Worked, but the Coil Still doesn't
Work. If all the above tests worked, there is probably a driver
board problem. Everything has been tested from the TIP102 back to the
coil itself. That only leaves the TIP102 itself, its pre-driver
transistor, and the logic chip that controls the transistors. It has
to be one (or more!) of these devices that are causing the problem.
Installing a New Transistor. If it has been determined a
coil's driver board transistor is bad, there are a few things to keep
in mind. Most TIP102 transistors also have a "pre-driver" transistor
(2N5401 for WPC-S and prior, or MPSD52 for WPC-95). Both 2N5401 and
MPSD52 transistors are basically the same (use either). They both
cross to NTE288.
If a coil's TIP102 transistor is replaced, it's a good idea to also
replace its corresponding pre-driver. It will be located near the
TIP102 transistor. See the schematics or the internal solenoid test
"help" to determine the specific pre-driver transistor(s).
Heavier duty coils use a bigger TIP36c driver transistor. These
transistors have TWO pre-drivers: a TIP102 and a 2N5401 (or MPSD52)
transistor. Again, if the TIP36c has failed, it's a good idea to
replace both corresponding pre-driver transistors.
Replacing the pre-driver transistors is optional (if they test Ok).
Test these pre-drivers instead of just replacing them. But if the
driver transistor has failed, the pre-driver was probably
over-stressed too. It is a good idea to replace the pre-driver
transistor(s) too.
Don't Forget the 74LS374 TTL Chip! If a coil locked on
really hard and for a period of time (and without blowing the coil
fuse, over fused?), the controlling 74LS374 chip may have also died.
If after replacing the TIP driver transistor(s) and the smaller
pre-driver transistor, the coil is still locked on, now is the time to
replace the 74LS374 TTL chip. Use the schematics and trace the
transistors in question back to the 74LS374 chip. This will be chip
U2, U3, U4, or U5 on WPC-S and prior driver boards, or chip U4, U5,
U6, or U7 on WPC-95 driver boards.
WPC Coil Diodes. On all electronic pinball games, each
and every CPU controlled coil must have a coil diode. This diode is
VERY important. When a coil is energized, it produces a magnetic
field. As the coil's magnetic field collapses (when the power shuts
off to the coil), a surge of power as much as twice the energizing
voltage spikes backwards through the coil. The coil diode prevents
this surge from going back to the driver board and damaging
components.
If the coil diode is bad or missing, it can cause several problems.
If the diode is shorted on, coil fuse(s) will blow. If the diode is
open or missing, strange game play will result (because the driver
board is trying to absorb the return voltage from the coil's magnetic
field collapsing). At worse a missing or open diode can cause the
driver transistor or other components to fail.
On non-WPC games, sometimes a diode
lead breaks on the coil from vibration. Also, when replacing a coil,
the operator can install the coil wires incorrectly (the power wire
should always be attached to the coil's lug with the banded side of
the diode). To prevent this, Williams moved the coil diode to the
Driver board. This isolates the coil diode from vibration and
eliminates the possibility of installing the coil's wires in reverse.
This was done on all coils except the flipper coils.
The coil
diodes on a Fliptronics flipper coil. The red
(bottom) wire is the "hot" wire. The yellow (middle) wire
handles the initial hi-power "flip", and the orange (top) wire
handles the flipper's "hold".
|
|
Flipper
coil wiring. Note the wire color rules specified below are the
"usual" wire colors (but can't be 100%
guarenteed).
|
|
The coil
diodes on a Non-fliptronics flipper coil. Note the solo
center wire and the all blue wire on the top lug goes to the
EOS switch and the 2.2 mfd 250 volt spark arresting capacitor
(the EOS switch and capacitor are wired in parallel). The
blue/yellow (lower) wire (or gray/yellow) is the "hot" wire.
The blue/violet (upper) wire continues to the cabinet switch,
the driver board relay, and ultimately
ground.
|
|
Even on WPC games, the coil diode can fail. The coil diode can be
tested. It is mounted on the driver board, near it's corresponding
driver transistor (refer to the schematics; it's the diode that is
tied to one of the legs of the driver transistor).
Use a DMM set to "diode" setting, and test the board mounted coil
diode. With the black lead on the banded side of the diode and the red
lead on the non-banded side, a reading of .4 and .6 volts should be
seen. Reverse the leads (red lead to banded side of diode), and a null
reading should be seen. If this reading is not indicated, cut one lead
of the diode from the driver board, and repeat the test. If these
results are still not seen, replace the diode with a new 1N4004 diode.
Installing a New Coil. Many replacement coils will come
with a diode soldered across its solder lugs. On WPC games, all coils
except the flipper coils have the diode mounted on the Driver board.
For all coils except flipper coils, cut the diode off the coil before
installing. Then solder the coil wires to either coil lug. The diode
can also be left in place, but the coil wires must be installed
correctly. The green (ground) wire MUST go to the lug of the coil with
the non-banded side of the diode. The power wire solders to the lug
with the banded side of the diode. If the wires are reversed, this
essentially causes a shorted diode. Though the Driver board mounted
diode is still present as protection, damage can occur to the coil's
driver board transistor.
Coil Doesn't Work Check List. If a coil doesn't work in a
game, here's a check list to help determine the problem.
Before starting, is the coil stuck on? (Hint: is there heat, smoke
and a bad smell?). If so, the coil's driving transistor has probably
failed. Turn the game off and check the driving transistor, and
replace if needed. See Transistors
Testing Procedures for more info.
If the coil just doesn't work, here's a list of things to check:
- Have the power wires fallen off the coil's solder lugs?
- Is the coil damaged? Has the internal winding broken off the
coil's solder lug?
- Is there power at the coil? See Testing for
Power at the Coil for more details.
- If there is no power at the coil, check its fuse. Use the
internal diagnostics and the "help" button to determine which fuse
controls the coil. See Testing
Transistors/Coils using the Diagnostics for details.
- Check the other coils that share one of the same wire colors.
Are they working too? If not, suspect the fuse that handles these
coils.
- Power to coils are often ganged together. If the power wire for
this coil has fallen off a previous coil in the link, power may not
get to this coil.
- Using the DMM and its continuity test, make sure the coil
connects to the correct connector/pins on the driver board. This
information can be seen from the Diagnostics solenoid test.
- Check the driving transistor. Usually this transistor will short
on when it fails, but not always.
3d. When things don't work: Game Resets (Bridge
Rectifiers and Diodes)
Game resets are probably the biggest problem with WPC to WPC-S
games (and to a lesser extent, WPC-95 games). The pinball will
seemingly shut off, then power back on (like the game was turned off
and back on quickly). Typically, this will happen during game play,
when the flippers are used. If the +5 volts (which powers all the
logic circuits) dips momentarily below 5 volts (from heavy voltage
draw when the 50 volt flippers are used), the "watchdog" circuit shuts
the game down. The high current draw flippers stresses the other power
components in the system. If these power components are starting to
fail, the +5 volts dips, and the watchdog circuit resets the game.
When the game shuts down, the power components under stress are
relieved. Then the voltage returns to +5 volts, and the game powers
back up. This reset process can happen anytime, but usually happens
during game play.
Check the Easy Stuff First.
Proper AC Wall Voltage? Important: Before starting
to dig in and try to diagnose the bridge rectifiers, set the DMM to AC
Voltage and test the wall socket voltage. Make sure there is
110 to 120 volts AC present! If there is only 100 volts, this can
cause the game to reset. If in Europe, and the game is set to 240
volts AC and yet there is only 210 volts at the wall plug, this can
also cause the game to reset too. This problem happens mostly in the
summer, when household power consumption is at a high, or if the game
is plugged into the same circuit as another high power device. WPC
pinball games draw a maximum of 8 amps of power. Most home circuits
are 15 amps, so two pinballs on one circuit should be the maximum.
Don't have the game plugged into the same circuit as another power
sucking device (like an air conditioner, refrigerator, etc.).
Re-seat the Transformer connectors. Though this doesn't
tend to be a big problem, try re-seating the connectors on the large
transformer in the bottom of the cabinet. Unplugging then plugging
these connectors effectively cleans them and makes sure they are
snuggly attached. If there is any resistance in the transformer plugs,
that can reduce the voltages going to the rest of the game. This only
takes a moment to do, so it's not a bad thing to try.
Flipper Coil Diodes. Though not a big problem on WPC
games, if the flipper coil diodes (there are two per coil) are damaged
or missing, this too can cause game resets. This is a lot more common
on games prior to WPC, but it can happen here too, and the diodes are
needed. If missing or broken, resets can happen on and WPC or WPC-95
game.
Failing Bridge Rectifiers, WPC-95 Diodes and
Filter Caps.
Bridge rectifiers or diodes (and their corresponding filter
capacitor) convert AC voltage to smooth DC voltage. This is very
important, as all the circuit boards run on DC voltage. If a game
plays fine, but randomly resets, often the bridge rectifiers (or
diodes) and their capacitor are over stressed and need replacement. On
WPC-S and prior games, a bad bridge rectifier is probably the single
most commonly failed component relating to game resets.
A bad bridge rectifier (or diodes on WPC-95), or cracked solder
pads around a bridge can also give game boot-up error messages saying
fuse F114/F115 (or F106/F101 on WPC-95) have failed, when the fuses
are actually good. See the Check the
Fuses section (and below) for a list of fuses and what bridges
they connect to.
WPC bridge rectifiers and diodes reside on the driver board
(although there is also a bridge on the Fliptronics board prior to
WPC-95). A bridge rectifier is mearly four diodes strung together in a
square. There are two AC input voltages, and two DC (positive and
negative) output voltages. These diodes are encased in epoxy, and
covered with a square metal casing.
Failed bridges/diodes can often short or "go open". BOTH of these
problems are quite common! A shorted bridge/diode will immediately
blow a fuse when powered on. An open bridge/diode will cause
lower or no voltage to get past the bridge. If the fuses are good,
but power driver board LEDs are not lit, this could be an indicator of
a bridge/diode that has "gone open".
Bridge
rectifiers on a WPC-S and earlier generation driver boards.
From the left to right: BR3, BR4, BR2 (top), BR1 (bottom). BR2
and BR1 have a large silver heat sink over
them.
|
|
The BR5
bridge used on WPC-S and earlier generation driver boards. Note
the "+" lead of the bridge is offset slightly, from an
otherwise perfect square shape. Notice the bridge is installed
about 1/4" above the board. This aids air flow and keeps the
bridge cool.
|
|
WPC-95 "Bridges". When WPC-95 was released, Williams
decided to stop using bridge rectifiers. Instead they just installed
four diodes right on the driver board for each replaced bridge. By
using four discrete diodes instead of a single bridge, the heat
generated by the components is spread out and reliability is greatly
improved. Bridge rectifier failure is very common in WPC-S and prior
systems. Replacement of even a single diode in the WPC-95 system games
is very rare (but these games are not as old as WPC-S and prior
systems). Certainly all the problems associated with the bridge
rectifiers can still be exhibited in a WPC-95 system too.
The diodes used in WPC-95 are called P600D (or 6A4 or 6A400). These
are 6 amp at 400 volt rectifiers. A substitute device is NTE5814.
WPC-95
P600D diodes D7 to D22 which replaced MB3502W/MB352W bridge
rectifiers. Also note the smaller "T" fuses (on the right)
used in WPC-95.
|
|
The Electrolytic Capacitor: the Bridge Rectifier and Diode's
Partner. Each bridge rectifier or diode set must also have an
associated electrolytic capacitor. These are needed to polish the
converted rough DC voltage to smooth DC voltage.
Electrolytic caps are largely mechanical devices. With time, they
can fail. Expect about 10 years maximum life from an electrolytic
filter capacitor. It is fairly common for these caps to fail. A
failing electrolytic capacitor can cause the game to reset, as the DC
voltage won't be "smooth". Because of this, when replacing the BR2
bridge on pre-WPC95 games, it is a good idea to also replace the
associated filter capacitor C5 (15,000 mfd 25 volts).
Smaller Filter Caps Used with WPC-95. Why? Interestingly,
Williams changed from 15,000 mfd (at C5) on WPC-S and prior, to a
lower value of 10,000 mfd on WPC-95 (at C9). With time, WPC-95 games
may be more sensitive to bad filter caps, because of this lower value.
Right now, since these games are fairly new (1996 and later), this
isn't a huge problem.
Higher filter cap values are generally good; they provide a better
level of AC filtering as the capacitor gets older. As electrolytic
capacitors wear (they really are a mechanical device), they are less
efficient at AC filtering, and their MFD value drops. However, the
higher the MFD value of a capacitor, the more strain it puts on the
rectifying bridge or diodes. When a game is turned on, the filter cap
draws significant current during the first half AC cycle (since this
power is used to "charge" the capacitor). This can subject the bridge
rectifier (or diodes) to an excessive in-rush of current. This in-rush
current can be up to ten times the current needed after the filtering
capacitor has charged. This can cause a connection inside a bridge to
instantly go open (this is not the same as over-current, which can
cause the bridge to short). In-rush current is a factor of both
voltage and the capacitor. A larger cap will force more in-rush
current to the bridge, potentially causing damage. Also capacitors
with higher MFD values cost more (the change from 15,000 to 10,000 mfd
could have been in fact a cost/availability issue; the 10,000 mfd
capacitors may have had a shorter lead time, and were cheaper for
Williams to buy).
Bridge Rectifier, Diode, and Filter Capacitor Device
List. Here's a list of what bridge rectifiers and diodes
control which functions, and their associated capacitors. All are
located on the driver board, unless otherwise stated.
WPC-S and Earlier Driver Board:
- BR1 to C6 & C7 (15,000 mfd @ 25v) to F114: +18
volts used for lamp driver columns. Then the 18 volts goes through
voltage regulator Q2 (LM7812) and F115, and is converted to 12
volts (regulated) for the switch matrix.
- BR2 to C5 (15,000 mfd @ 25v) to F113: +5 volts. The
bridge and cap that fail the most.
- BR3 to C8 (100 mfd @ 100v) to F112: +50 volts, used for
solenoids.
- BR4 to C11 (15,000 mfd @ 25v) to F111: +20 volts, used
for flash lamps.
- BR5 to C30 (15,000 mfd @ 25v) to F116: +12 volts
unregulated for playfield devices, dot matrix display, and the
coin door.
- BR1 (on Fliptronics II board) to C2 (100 mfd @ 100v) to
F901-F904: +50 volts used for the flippers. Located on the
Fliptronics II board.
WPC-95 Driver Board:
- D3, D4, D5, D6 to C8 (10,000 mfd @ 35v) to F109: +12
volts unregulated for playfield devices, dot matrix display, and
the coin door.
- D7, D8, D9, D10 to C9 (10,000 mfd @ 35v) to F105: +5
volts for all board logic circuits. The diodes and cap that
fail the most.
- D11, D12, D13, D14 to C12 (10,000 mfd @ 35v) to
F106/F101: +18 volts used for lamp driver columns. Then the 18
volts goes through voltage regulator Q2 (LM7812) and F101, and is
converted to 12 volts (regulated) for the switch matrix.
- D15, D16, D17, D18 to C10 (10,000 mfd @ 35v) to F109:
+20 volts for flash lamps.
- D19, D20, D21, D22 to C22 (100 mfd @ 100v) to
F102/F103/F104: +50 volts for solenoids.
- D25 to D32: +6.3 volts for general illumination. These
were replaced with jumpers starting with Scared Stiff. See the Burnt
Connector section (WPC-95 GI diodes D25-D32 remove and jumper)
for a description of this.
Testing a Bridge (WPC-S and prior), Board
Removed. Note testing a bridge with the game off is NOT
conclusive to whether the bridge is bad! The bridge is being tested
under NO load. Only a bridge which is shorted (and hence is blowing
fuses) or open will test as "bad". A bridge could test as "good", and
still cause the game to reset. Also testing a bridge "in circuit"
(while still soldered in the board) can often not give proper results.
A bridge has four terminals: two AC terminals, and two DC terminals
(postive and negative). On the side of each bridge, printed on the
metal casing, there will be two labels: "AC" and "+". From the solder
side of the driver board, mark with a Sharpie pen these two terminals.
Figuring out the other two terminals is easy: the other AC terminal is
diagonal to the labeled AC lead. The negative DC lead is diagonal to
the labeled positive DC lead. Mark these right on the board with the
Sharpie pen. To double check, the two DC leads (positive and negative)
connect to that bridge's respective electrolytic capacitor, and it's
positive and negative leads. Testing a bridge while soldered in the
board (in curcuit) may not give the following results. For example,
testing BR2 in curcuit will not give these results (but most of the
other bridges will). To test the bridge:
- Put the DMM on diode setting.
- Put the red lead of the DMM on one of the AC terminals.
- Put the black lead of the DMM on the positive DC lead. A reading
of between .4 and .6 volts should be indicated.
- Put the red lead of the DMM on the other AC terminal. Repeat
step #3.
- Put the black lead of the DMM on one of the AC terminals.
- Put the red lead of the DMM on the negative DC lead. A reading
between .4 and .6 volts should be indicated.
- Put the black lead of the DMM on the other AC terminal. Repeat
step #6.
If values outside of .4 to .6 volts are shown for any of the above
tests, the bridge is bad. Typically you will get a zero value (a
short) for at least one of the above tests in a bad bridge.
Testing a Bridge (WPC-S and prior), Under Load, In the
Game. This tip is from John Robertson. This test is a more
conclusive way to test a bridge. This procedure requires a DMM, two
alligator jumper wires, and a 6 amp rectifying diode (6A50 or 6A2 or
6A4, or whatever is available; Radio Shack sells 6A50 diodes, part
number 276-1661). Here is the procedure:
- With the game off, clip one end of an alligator test wire on the
"+" lead of bridge BR2 (top most bridge) on the driver board. The
"+" lead is the top left most lead (see picture below). Often the
side of the bridge is labeled too. One lead is "AC", and the other
is "+" (connect the alligator clip to the "+" lead, which is the
left lead as facing the board).
- Connect the other end of the alligator test wire on the RED lead
of the DMM.
- Put the BLACK lead of the DMM on the braided metal grounding
strap at the bottom of the backbox.
- Turn the DMM on, and set it to DC Volts (20 volt range).
- Turn the game on. A value of 12 to 13 volts should be shown. Any
less than 12 volts, and the bridge (or the connection to the bridge)
is bad.
Attaching
the red alligator test lead to the "+" leg of bridge BR2. The
other end of the alligator lead is attached to the DMM's
red probe.
|
|
- Turn the game off. Take the second alligator jumper wire, and
connect the clip to the BANDED end of the 6 amp diode.
- Connect the other loose end of the alligator jumper wire to
where the first alligator clip connects to the red lead of the DMM
(see picture below). This is essentially the same as connecting the
second alligator clip to the "+" lead of bridge BR2 (but there is
not enough room at the bridge to do this, since the first alligator
clip is in the way).
- Turn the game on.
- Touch the non-banded end of the diode to connector J101 in
either pin 1 or 2 (two top most pins). Note the IDC connector will
have some exposed metal at the top of the connector to touch, and
plug should not be removed.
- While doing the above step, examine the DMM voltage reading. If
the voltage rises when the diode lead is touched to Connector J101
pin 1 or 2, the bridge BR2 is bad (bad internal positive diode).
A second
alligator clip is connected to where the first alligator clip
connects to the red lead of the DMM. Now touch the second
alligator clip with a 6 amp diode, NON-BANDED end, to
connector J101 pins 1 or 2. The voltage on the DMM should
NOT drop when the diode is touched to connector J101 pins 1 or
2.
|
|
- Turn the game off. Reverse the diode in the alligator clip so
the NON-BANDED end of the 6 amp diode is connected to the alligator
clip.
- Connect the other end of the alligator clip to TP5 (ground).
- Turn the game on.
- Touch the banded end of the diode to connector J101 in either
pin 1 or 2 (two top most pins). Note the IDC connector will have
some exposed metal at the top of the connector to touch, and the
plug should not be removed.
- While doing the above step, examine the DMM voltage reading. If
the voltage rises when the diode lead is touched to Connector J101
pin 1 or 2, the bridge BR2 is bad.
If the above tests all work as described (no voltage drops or
readings below 12 volts), the problem is mostly likely a bad C5
(15,000 mfd 25 volt) filter cap (or a cracked solder joint to the
bridge and/or capacitor, which can be solved by installing the jumper
wires described below).
The second
alligator clip is now connected to TP5 (ground), and the diode
is reversed in the alligator clip. Touch the other end of the
second alligator clip with the 6 amp diode, BANDED end, to
connector J101 pins 1 or 2. The voltage should not drop when
the diode is touched to connector J101 pins 1 or
2.
|
|
Testing a Diode (WPC-95) The diodes that replaced the
bridge rectifiers in WPC-95 are even easier to test. Again, testing
diodes in curcuit may not give the following results.
Also, testing a diode is NOT conclusive to whether the dioide is
bad! The diode is being tested under NO load. Only a diode which is
shorted (and hence is blowing fuses) will test as "bad". A diode could
test as "good", and still cause the game to reset.
- Put the DMM on diode setting.
- Put the black lead of the DMM on the banded lead of the diode.
- Put the red lead of the DMM on the non-banded lead of the diode.
- A reading between .4 and .6 volts should be indicated.
The Above Bridge/Diode Tests Don't Always Work! Yes, you
heard right. The above outlined bridge and diode tests above don't
always find a faulty component. These devices can just start to fail,
and this will cause the game to reset. But a bridge or diode can
become "leaky", which will cause the game to reset, and may not show
as bad in the above tests (though the bridge test "under load" as
explained above is the most accurate of the tests).
So what do you do now? How can you be sure the resetting game has a
bad bridge or diode? Well you really can't! First make sure the wall
voltage is at the proper level. Then re-solder the bridge/diodes and
their associated capacitor's solder pads. Then just go ahead and
replace the suspected bad bridge/diode (BR2 or D7, D8, D9, D10 on
WPC-95). If the game is still resetting, replace the associated filter
capacitor (C5 or C9 on WPC-95). If the game is still resetting,
replace the LM339 voltage comparitor at U6 (U1 on WPC-95) as a last
resort.
Replacing a Bridge or Diode. Replacement is as simple as
cutting out the old component and soldering in a new one. When
installing the new bridge, mount it 1/4" or even 1/2" above the board.
This allows for air to flow underneath the bridge for better cooling.
Replacing BR1 and/or BR2 on WPC-S and Prior. When
replacing either (or both) bridges BR1 and BR2 on WPC-S and prior,
both bridges will have to be dealt with. These two bridges share a
single large silver heat sink. Since they both share the same heat
sink (and one failed due to heat), the other probably will need
replacement shortly. If either BR1 or BR2 is bad, replace them both.
To remove them, both will need to be unsoldered from the Driver board,
and the heat sink un-screwed from the bottom of each bridge. The new
bridge is then screwed to the heat sink, and both bridges
re-installed. There should be some white heat sink compound on the top
of the bridges too. Make sure to add some heat sink compound when
replacing the bridges. Heat sink compound can be purchased at Radio
Shack.
Replacement Bridges and Diodes. The stock bridge
installed in WPC games is 35 amps at 200 volts. The original part
number will be something like "MB3502W" or "MB352W". The "MB"
signifies a metal cased bridge. The "35" signifies 35 amps. The "02"
or "2" signifies 200 volts peak. The "W" at the end means the bridge
has wire leads. Higher amps or voltage ratings work fine. I generally
use 35 amps at 400 volts for example.
Replacement wire lead bridges are available from Competive Products
Corp (800-562-7283), or from Williams, part number 5100-09690. Mouser also sells them, part number
625-GBPC3502W ($3.48). And so does Digikey, part number MB352WMS-ND.
Radio Shack even sells 35 amp bridges at 50 volts (which isn't enough
voltage). But look at the bridge inside the Radio Shack package, as
often they are labeled 3502W or 352W (35 amps 200 volts), and not 50
volts. Always buy only the labeled bridges from Radio Shack. Sometimes
these "35 amp" bridges are labeled 1001W (10 amp 100 volts!).
Obviously put that one back and grab another!
Replacement diodes for WPC-95 boards are P600D (6A4 or 6A400), or
NTE5814. A lower voltage version can be used too, 6A2 or 6A200 (200
volts). Radio Shack sells a 6 amp 50 volt (6A50) version which can be
used in a pinch, part number 276-1661.
Testing the Filter Caps. Testing the filter capacitors on
the driver board is fairly easy. With the game on, set the DMM to AC
volts. Then put the leads of the DMM across the two leads of each
filter capacitor (doesn't matter which DMM lead to which capacitor
lead, as AC voltage is being measured). If more than 0.30 volts AC is
seen, the capacitor is bad.
The problem with this test is the leads for the filter caps are
nearly impossible to access, when the board is installed in the game!
For this reason, I usually just replace the filter cap in question (C5
or C9 on WPC95) when in doubt.
Replacement Filter Caps. If replacing a filter capacitor,
use a 15,000 mfd 25 volt "snap" cap (on any WPC generation, even
WPC-95). Higher voltage caps can be used (but are more expensive). Do
not use a capacitor greater than 15,000 mfd, because the in-rush
current puts more stress on the rectifying bridge/diodes. A lower
value of 10,000 or 12,000 mfd could also be used (but no lower than
10,000 mfd). These are available from many sources, such as Digikey
(http://www.digikey.com/ or
800-344-4539) or Mouser (http://www.mouser.com/ or
800-346-6873):
- 15,000 mfd 25 volt, Mouser part# 5985-25V15000 $4.63 each, or
Digikey part# P6577-ND $5.52 each.
- 12,000 mfd 25 volt, Mouser part# 5985-25V12000 $4.95 each, or
Digikey part# P6575-ND $4.74 each.
- 10,000 mfd 25 volt, Mouser part# 5985-25V10000 $3.65 each, or
Digikey part# P6573-ND $4.17 each.
Reflowing Bridge or Diode Solder Joints. Often a bridge
or diode will test Ok, but the game still resets. This can be caused
by cold, fatigued, or cracked solder joints on a bridge. Since bridges
(especially BR2) and diodes can get hot, they will mildly heat up a
solder joint, and make it go "cold" or fatigued. Reflowing these
solder joints with new solder often fixes this problem. Also reflow
the solder joints on the bridge or diode's associated filter
capacitor. Often these solder joints crack.
The problem with reflowing the solder joints on the bridges and
capacitors is this; often the traces on the top side of the board
(which can not be accessed because of the components), do not get as
good solder contact. This can cause an intermittent connection, which
can lead to game resets. The best solution to this problem is adding
some jumper wires (see below).
Insurance: Installing Bridge/Capacitor Jumpers. Another
problem with the bridge rectifiers/diodes and the filter capacitors
are their solder pads. The WPC driver board is a double sided board
(that is, it has "traces" running on both sides of the board, both
leading to different components). Soldering of both top and bottom
traces is done on the bottom (solder side) of the board. Since the
components themselves are in the way on the top side of the board, it
is hard to even see the component side solder pads.
The problem is this; these components (bridges/capacitors) are
large, and they can get hot (softening the solder). Vibration, heat,
or both, can cause the solder points to crack. This can cause an
intermittent connection. This can cause game resets, or whole banks of
coils or lamps to not work.
Reflowing the solder on the back of the driver board is one
solution. But it really isn't the ultimate solution. Since the driver
board is a double sided board, and the components on the top side of
the board are large, the traces can only be soldered on the bottom
side of the board. This does not guarentee a good connection to the
traces on the top (component) side of the board. To fix this problem,
it is recommended to add jumper wires on the solder side of the driver
board. This is done to back up the bridge/capacitors' component side
board traces.
The most important bridge/capacitor to jumper is BR2 and C5. Jumper
two 18 guage wires on the solder side of the driver board from BR2 to
C5 (positive lead of BR2 to positive lead of C5, and negative lead of
BR2 to negatvie lead of C5). This will help prevent random game
resets. All the other bridges/capacitors can be jumpered too.
Installing the Jumpers. When installing the jumpers,
first label the back of the driver board. Use a "sharpie" pen and
label the bridge, and its "+" and "-" leads, on the back side of the
driver board. The positive lead of the bridge is the one offset
lead in the square. The negative lead is diagonal the postive lead.
The other two diagonal legs are the AC leads. Also label the
capacitor and it's positive lead with a sharpie pen (the positive lead
on most of the filter caps is the "top" lead). Double check all
potential connections with a DMM, and buzz out the jumper paths BEFORE
you install them (installing a jumper incorrectly can cause SERIOUS
problems!). This will make installing the jumpers much easier and
error-free.
Here is a list of jumper wires that should be added to WPC and
WPC-S driver boards. For reference, the driver board is positioned
with the solder side showing, and connector J104 at the "top":
- BR2 to C5: two jumpers. Jumper the positive lead of bridge BR2
to the positive lead of C5. Repeat for the negative leads also.
- BR1: ONE jumper. Jumper the AC lead of BR1 (just below the
positive lead) to connector J101 pin 7.
- C6/C7: jumper the two positive leads of capacitors C6 and C7
together (this also jumpers also helps BR1).
- BR3: three jumpers. Jumper the lower AC lead of BR3 (just below
the positive lead) to connector J104 pin 1. Jumper the other upper
AC lead (to the left of the positive lead) to connector J104 pin 2.
Jumper the positive lead of BR3 to the large solenoid fuse trace
about 2" below the bridge (see picture below).
- BR4: three jumpers: Jumper the negative lead of BR4 to the
negative lead of C11. Jumper the AC lead of BR4 (just above the
negative lead) to connector J102 pin 1. Jumper the other lower AC
lead of BR4 (just below the positive lead) to connector J104 pin 4.
- BR5 to C30: two jumpers: Jumper the positive lead of BR5 to the
positive lead of C30. Repeat for the negative leads also.
All the above
jumpers have been installed. The most important jumper is the
one from BR2 to C5 (the gray wires). Note the "+" (offset leg) of
the bridge goes to the "+" lead of the associated capacitor. The
"-" lead of the bridge is diagonal to the offset "+" lead. Shown
is a WPC and WPC-S style driver board.
|
|
Probably
the second most important jumpers to install are those from BR5
to C30. Note the "+" (offset leg) of the bridge goes to
the "+" lead of the associated capacitor. The "-" lead of the
bridge is diagonal to the offset "+" lead. Shown is a WPC and
WPC-S style driver board.
|
|
Are Jumper Wires Good Insurance for WPC-95 Games
Too? Yes! Even though WPC-95 games stopped using bridges in
favor of diodes (which have far less heat/vibration solder pad
cracking problems), jumper wires are still a good idea. On WPC-95
games, all the large electrolytic capacitors on the driver board have
the potential for cracked solder pads.
To give an example of solder pad cracking, I recently had a problem
on a Safe Cracker (WPC-95) where none of the low power (20 volt) coils
worked. It was very frustrating; the fuse was good, and power was
getting to the Driver board, but not out of the driver board and to
the coils.
It turned out that the capacitor that filters the DC voltage after
the bridge rectifier on the Driver board had a cracked solder pad.
This prevented the voltage from getting any further than it's
associated bridge rectifier (I should have known; the +20 volt LED on
the Driver board was not lit!). Adding the jumper wires from the
bridge to the capacitor fixed the problem.
Replace the Filter Capacitor at C5 (or C9 on WPC-95). If
the game is still resetting, there's probably a good chance that the
filter capacitor at C5 (15,000 mfd @ 25v) or C9 (WPC-95, 10,000 mfd @
25v) needs to be replaced. The C5/C9 capacitor filters and smooths the
+5 volts. If this cap is worn out, unsmooth +5 volts will result. This
will cause random game resets. On WPC-S and prior games, when
replacing bridge BR2, it is a good idea to just go ahead and replace
the filter cap C5 with a new 15,000 mfd 25 volt capacitor.
Check the Power Driver Voltage Plugs. The molex plug that
provides the input voltage to the driver board can also have problems.
On WPC-95, J129 supplies the voltage that gets rectified to +5 volts.
On WPC-S and prior, J101 handles this. Also check the main power plugs
that supply +5 and +12 volts to the power driver boards. On WPC-S and
prior, this is J114. On WPC-95, this is J101.
Make sure the above connectors are in good condition. Check the
pins on the driver board for burnt pins, cold/fatiqued or cracked
solder joints (also see the Burnt
Connector section). Any problems with the above mentioned
connectors can cause random game resets.
Game is Still Resetting. As a last thing to check, the
LM339 voltage comparator at U6 (U1 on WPC-95) on the power driver
board could be bad. This chip is in the zero crossing circuit. If bad
or leaky, this will cause game resets too. Replace the LM339, and make
sure to install a socket for this chip.
Yet another reset problem can be caused by the CPU board chips at
U1, U2, U3 and U5 (all WPC revisions). These chips connect directly to
the CPU, and can have heat problems that cause a game to reset.
Last Reset Resorts - Failing Dot Matrix
Controller/Display. The game in question was Star Trek Next
Generation, and the symptoms included occasional game resets, weak
flippers, and dim lights. The usual stuff was tried: replaced all the
bridge rectifers and filter caps, rebuilt the flippers, etc, and
nothing worked. A bad transformer was suspected, so it was re-taped
for 100 volts, as an experiment. After powering the game back on,
immediate smoke was seen off the dot matrix display controller board.
On closer inspection, a number of the diodes and large resistors on
the dot matrix display board showed signs of severe heating (the
experiment with the lower voltage tap wasn't nearly long enough to
cause the damage observed - this had built up over considerable time).
After rejumpering the game back to 115 volts, a spare dot matrix
display board was installed in the game, and everything worked: bright
lights, strong flippers, and no game resets.
In this case the high-voltage supply circuits on the dot matrix
display controller board were marginal. A considerable amount of
current was being drawn by the dot matrix display board. This problem
caused enough load on the transformer to bring all the voltages down
for the whole game (there was a clue: with the game turned on, the AC
inputs into the bridge rectifers all read at the low end of the
acceptable range).
Even having an "out-gassed" dot matrix display with a good dot
matrix controller board can cause game resets (see Dot
Matrix/AlphaNumeric Score Displays for more details on out-gassing
displays). The problem of weak, old, out-gassed dot matrix displays
causing game resets is becoming more common. The moral of this story
is to not use a dot matrix display that is out-gassed and at the end
of its life.
Lesson: not all game resets and low voltage problems are caused by
the notorious bridge rectifers. Bad CPU chips or bad voltage supply
circuits on the dot matrix display board can also mimic these
problems. Check the large resistors and diodes near the heat-sunk
transistors on the dot matrix controller board. Look for clear signs
of overheating (blackened PC board), even though the board is
functional. To fix this, rebuild the high voltage section of the dot
matrix display board, as described later in this document in the Dot
Matrix/AlphaNumeric Score Displays section. Also be sure to
replace a marginal dot matrix display. A bad display can consume much
more power, stressing the dot matrix controller board, and potentially
lowering other voltages, and causing game resets.
The Thermistor and Resets. The Thermistor's job is to act
like a low value resistor when cold. After warming up for a minute, it
essentially becomes a zero ohm resistor. When the game is first turned
on, it provides a slightly lower input voltage to the game's
transformer (and hence bridge rectifiers), limiting the in-rush
current (and lengthening the life of the bridges). But with time,
sometimes the thermistor does not function correctly after warm up,
therefore acting like a full time resistor. This keeps the input
voltages lower, and makes game resets more prevalent. The Thermistor
is located in the "power box" just inside the coin door. This power
box also housing the game's power switch.
With the game turned on and warmed up (five minutes), no more than
1.00 volts AC should be seen across the Thermistor, with the game in
the attract mode (not playing). Please be careful as there is 115VAC
(or 220VAC for Europe) in this box and can be dangerous.
The "power
box" just inside the coin door. Picture by John
Robertson.
|
|
Measuring
the AC voltage across the Thermistor, with the game in attract
mode. No more than 1.00 volts AC should be seen. Picture by
John Robertson.
|
|
Fuse F116 Keeps Blowing on WPC-S and Prior
Games. When fuse F116 keeps blowing on WPC-S and earlier games,
it's almost always a bad bridge rectifier at BR5. Replace and make
sure there is good solder contacts leading to the "+" lead of C30.
"Check Fuse F114/F115" (or F106/F101) Message. This
indicates the voltage is out for the lamp/switch matrix. Sometimes
this message is gotten even when the fuses are good!
A failing bridge (or diodes) can cause the game to think their
respective fuses are bad. If the fuse F114 (or F106 on WPC-95) is
actually blown, usually this is an indication that BR1 (or diodes
D11-D14 on WPC-95) usually failed. But it could be as simple as a
cracked solder pad on power driver board's BR1 (or diodes D11-D14 on
WPC-95). See the above about jumper wires, and install those for good
reliability. The shotgun method can also be used, replacing BR1 (and
BR2, both for WPC-S and prior, while you are at it!) on the power
driver board, in addition to the jumper wires.
Here is a step-by-step test to see exactly what is causing the
F114/F115 (or F106/F101) error message. With the game on and the coin
door closed:
- Test for AC voltage at J101 pins 4 and 7 (or J129 pins 4 and 7
on WPC-95). A reading of 13 to 18 volts AC should be seen. This is
the AC voltage coming from the transformer. If no voltage here,
check the Molex connectors around the transformer and at the power
driver board.
- Test for DC voltage at TP8 (or TP102 on WPC-95) and ground. A
reading of 16 to 18 volts DC should be seen. If no voltage here,
replace BR1 (or D11 to D14 on WPC-95). Also no voltage here can
occur because the solder pads are cracked around bridge BR1 (or D11
to D14 on WPC-95). Using jumper wires for BR1 (as described in the
Game
Resets section) helps prevent this.
- Test for DC voltage at TP3 (or TP100 on WPC-95) and ground. A
reading of 12 volts DC should be seen. If no voltage here, check or
replace diodes D1 and D2 (1N4004, all WPC version).
- If diodes D1/D2 are OK, replace Q2 (all WPC versions), a LM7812
voltage regulator.
- If the above still does not fix the problem, replace U20 (all
WPC versions) on the CPU board (ULN2803). If U20 died "hard", it
could also blow the 74LS374 at U14 (on WPC-95 it's U23, a 74HC237)
on the CPU board.
- If the above still does not fix the problem, and the game has an
under-the-playfield optic board, replace the LM339 chips on this
board. Replace them all, and use sockets.
- If voltage is still not right, or BR1 (or diodes D11 to D14 on
WPC-95) are REALLY hot, check all the TIP107 transistors on the
power driver board. If these test good, check/replace the power
driver board's ULN2803 at U19 (or U11 on WPC-95), or maybe the power
driver board's 74LS374 at U18 (or U10 on WPC-95).
ALso on WPC-S and prior games, connectors J114, J116, J117, J118
can be removed. Replace the fuse and power on the game. If the fuse
blows, its corresponding bridge rectifier is most likely shorted and
should be replaced. If the fuse doesn't blow, the problem is not in
the circuit boards. Most likely a shorted wire, which can only be
manually hunted down.
Burnt +18 Volt BR1 Bridge or WPC-95 Diodes D11-D14. This
problem is strange, but a lot more common than one might think. The
+18 volt (lamp columns) bridge or WPC-95 diodes get excessively hot
and burns. I've seen this where the driver board is black from the
heat. This happens because the lamp matrix is demanding more power
than the circuit is designed to handle. Eventually the associated fuse
F114 or F106 (WPC-95) will blow. Note the BR1 bridge or WPC-95 diodes
D11-D14 are probably OK. If these were bad, the fuse F114 or F106
(WPC-95) would blow immediately.
The reason for the burned bridge or diodes is simple; for some
reason, one (or more!) of the lamp columns is stuck "on". Remember,
the lamp matrix uses 12 volts, but this is derived by strobing
(turning on and off very quickly) 18 volts. If a column locks on,
instead of getting 12 volts, the full 18 volts is delivered. This
added voltage puts stress on the lamp column circuit, and causes the
+18 volt BR1 bridge or WPC-95 diodes D11 to D14 to get really hot (and
their associated fuse to eventually blow).
To fix this, first check all the TIP107 column driver transistors
(see the Checking
Transistors section). If none of these transistors are shorted on,
then next suspect the ULN2803 at U19 (or U11 on WPC-95), or maybe the
74LS374 at U18 (or U10 on WPC-95). If the TIP107 transistors are OK,
the ULN2803 is probably the culprit. An easy way to tell if the lamp
matrix has a problem is to notice the controlled lamps right when the
game is turned on. If any playfield lamps flash on right at power-on,
there may be a problem with the ULN2803 driver chip.
Exploding +20 volt Capacitor. There are cases when the
+20 volt capacitor (Driver board C11 on WPC-S and prior, C10 on
WPC-95) can just explode. This happens when a shorted flipper coil
diode or shorted transistor on the Fliptronics board causes the 70
volt coil power to feedback into the 20 volt flashlamp circuitry.
Because of reverse voltage, this blows the 20 volt capacitor. Also
installing one of the ribbon cable connectors in the backbox on the
header pins (top row of header pins to bottom row of housing) can do
the same thing. And lastly, if connector J124 is mistakenly plugged
into the driver board connector J128 (they are keyed alike!), this can
cause capacitor C11 to explode.
First check the ribbon cable header pins to make sure they are
attached correctly. Then check the flippers. If when the flippers are
activated, one of the flashlamps dimly lights, there may be a bad
flipper transistor on the Fliptronics board.
There is a preventive measure which can be taken for this. Install
a blocking diode on the driver board ceramic 10 watt resistor R224 (or
R9 on WPC-95). To do this, first remove the lower leg of resistor
resistor R224 (the leg just above TP7). Connect the anode (non-banded
end) of a 1N4004 (or 1N4007) diode to the resistor's leg. Then solder
the cathode (banded side) of the diode back into the driver board
(where one leg of R224 was removed). This will prevent the problem.
3e. When things don't work: Problems with
Flippers
Flippers connect the player to the pinball game. Having perfectly
working flippers is extremely important. Here are some common flipper
problems and answers.
Remember, all flippers (regardless of the game) will have EOS (end
of stroke) switches. This tells the CPU a flipper is at full
extension. If this switch is broken, it could cause problems
(depending on the WPC generation). Bad EOS switches should always be
fixed.
How Flippers Work. Flipper coils are actually two coils
in one package. The "high power" side is a few turns of thick gauge
wire. This provides low resistance, and therefore high power. The "low
power", high resistance side is many turns of much thinner wire. This
side of the coil is important if the player holds the cabinet switch
in, keeping the flipper coil energized. The high power low resistance
side of the coil is only active when the flipper is at rest.
To simplify how the two sides of a flipper coil work, it's best to
examine the non-fliptronics version. In this case, when the flipper is
energized and at full extension, the normally closed EOS switch opens.
This removes the high powered side of the coil from the circuit. The
low powered side of the flipper coil is always in the circuit, but is
essentially ignored when the high powered side is in the circuit. This
happens because the current takes the easiest path to ground (the low
resistance, high power side of the coil). The low power high
resistance side of the flipper coil won't get hot if the player holds
the flipper button in.
A
simplified drawing of the flipper circuit in non-fliptronic
games.
|
|
EOS Switches: Normally Closed or Normally
Open? Pre-fliptronics games have a high voltage, normally
closed end-of-stroke (EOS) switch. But Fliptronics flippers are
basically an electronic (instead of mechanical) version of the above
explained non-fliptronics flippers. The main difference is fliptronics
flippers have EOS switches that are low voltage, normally open
switches (instead of high voltage, normally closed as used on
non-fliptronics flippers).
Is the problem Mechanical or Electrical? Before diving
into any flipper problem, identify if the problem is mechanical or
electrical. For example, if a flipper gets stuck in the "up" position
during a game, is it a mechanical binding problem, or an electrical
problem? In this case it's simple to tell; just turn the game off! If
the stuck flipper falls back to rest, the problem is electrical. If
the flipper stays in the up position, it's a mechanical problem.
Knowing this will help fix flipper problems.
Flipper Diodes. All WPC games will have diodes attached
at the flipper coil. Make sure these diodes are oriented like the ones
pictured below.
The coil
diodes on a Fliptronics flipper coil. The red (bottom) wire
is the "hot" wire. The yellow (middle) wire handles the
initial hi-power "flip", and the orange (top) wire handles the
flipper's "hold".
|
|
Fliptronics flipper coil wiring. Note the wire
color rules specified below are the "usual" wire colors (but
can't be 100% guarenteed).
|
|
The coil
diodes on a Non-fliptronics flipper coil. Note the solo
center wire and the all blue wire on the top lug goes to the
EOS switch and the 2.2 mfd 250 volt spark arresting capacitor
(the EOS switch and capacitor are wired in parallel). The
blue/yellow (lower) wire (or gray/yellow) is the "hot" wire.
The blue/violet (upper) wire continues to the cabinet switch,
the driver board relay, and ultimately
ground.
|
|
If the flipper(s) don't work at all...
Non-Fliptronics Games:
- Check the flipper fuses on the driver board, fuses F101 and
F102.
- On non-fliptronics games, clean the flipper cabinet switch
contacts and the EOS switch contacts with a small metal file. Make
sure this normally closed EOS switch is adjusted properly.
The switch should open about 1/8" at the flipper's end of stroke.
If this switch is dirty or not closed, the flippers may not work
at all.
- Check the DPDT flipper engage relay on the driver board. When
this relay is energized, it completes the ground path for all the
flippers. Transistor Q99 (2N5401) controls this relay (if this
transistor is shorted, the flippers will always work even when the
game is over). There are also two jumpers W4 and W5 on the driver
board which should NOT be installed (if these jumpers are
installed, the flippers will always be activated, even when the
game is over).
Fliptronics Games:
- Check the flipper fuses on the Fliptronics board.
- Use the internal WPC test software to test the flipper
switches. Press the "test button", and go to "Test Switch Edges".
A matrix chart will appear. The flipper switches are connected
directly to the CPU board (on WPC-95) or the Fliptronics board (on
earlier games) through direct switches, and not through the switch
matrix (non-fliptronics games have the flipper switches and
EOS switches wired directly to the flippers, and don't connect to
any board). This means if the flipper button is pressed on any
Fliptronics and later game, the circles on the right most column
(outside the box) of the matrix should change to a square. Here is
the order for that matrix column, from top to bottom:
- Lower Right Flipper EOS switch
- Lower Right Flipper button
- Lower Left Flipper EOS switch
- Lower Left Flipper button
- Upper Right Flipper EOS switch
- Upper Right Flipper button
- Upper Left Flipper EOS switch
- Upper Left Flipper button
If the EOS switches aren't
working on a Fliptronics or later game, check the continuity with
a DMM from the switch to the CPU board (on WPC-95), or the
Fliptronics board (on earlier games). On pre WPC-95 games, these
direct EOS switches go to the Fliptronics board connector J906 and
the flipper opto switches go to J905. On WPC-95 games, the direct
EOS switches go to the CPU board connector J208 and the flipper
switches go to CPU board connector J212. Non-fliptronics games
have the flipper switches and EOS switches wired directly to the
flippers, and don't connect to any board.
- On fliptronics games, if the flipper button doesn't register
in the above test, check the flipper
opto boards. Flipper opto boards were implemented on Addams
Family, mid-production (some Addams have them, some don't). Also
if the game uses plastic flipper opto activators, often these can
warp. This will cause the activator to not clear the "U" shapped
opto on the flipper opto board, causing a flipper to never
energize!
- On fliptronics (before WPC-95) games, there can be a very rare
and unusual problem with the fliptronics board. There is +50 volts
power at the flipper coils (and the coils & diodes are good),
but flipper switches just don't seem to work. This can be caused
by a failed flipper switch input chip at location U5 (74HCT244) on
the fliptronics board.
Optos are
used on fliptronics flipper switches. Note the
plastic activator arm that moves between the "U" shaped
optos. Originally Williams made these from metal, but
switched to plastic to save money. The plastic version can
often warp so they don't clear the opto, causing a flipper
not to work.
|
|
If the flipper button works fine in diagnostics, but the
flipper doesn't work...
All WPC Games:
- Check for +50 volts at the flipper coil. Put the DMM on DC
voltage. Put the black lead on ground (metal side rail of game).
Put the red lead on either of the outside lugs of the coil. A
reading of 50 to 80 volts on either lug should be indicated. No
voltage means (the coin door is open on 1993 or later games or) a
fuse is blown, or a wire has broken.
- Test the coil itself. To do this, turn the game on and leave
it in attract mode. Then attach an alligator test lead to ground
(metal side rail of game), and momentarily touch the other end of
the test lead to the middle lead of the flipper coil. The coil
should activate. This works on both Fliptronics and non-Fliptronic
WPC games.
- Check the flipper coil with a DMM set to ohms. With the game
turned off, try this:
- Notice the three solder lugs for the flipper coil. One of
the outside lugs has both a thick and thin coil winding attached
to it. This is the "common" lead.
- Put one lead of the DMM on the outside common flipper lug
(the one with the thin and thick coil windings attached to it).
- Put the other lead of the DMM on the middle lug. A reading
of about 4 ohms should be indicated. This is the high powered
side of the coil.
- Put the leads of the DMM on the two outside lugs of the
coil. For fliptronics games, a reading of about 125 ohms should
be seen. For non-fliptronics games, a litle more than 4 ohms
should be seen until the the flipper is moved manually to the
full extended position, opening the EOS switch. Now about 125
ohms should be indicated.
- If approximately these readings are not seen, the flipper
coil is bad. Typically the hold side of the coil goes bad more
often that the power side.
- Test the flipper diodes. To do this cut one lead of each diode
off the coil lug. Then set the DMM to the diode setting. Put the
black lead of the DMM on the banded side of the diode. A reading
of .5 volts should be seen. Reverse the leads and no (null)
reading should be shown. When done, re-attach each diode lead.
If the flipper works, but...
Non-Fliptronics Games:
- Flipper seems to work fine, but gets very hot and eventually
starts to burn and smell. Often the flipper will get stuck in the
"up" position. On non-fliptronic games, the EOS switch contacts
are not opening when the flipper is fully extended. Or the EOS
switch capacitor has shorted on.
Fliptronics Games:
- When activated, doesn't hold up (the flipper "flutters"). This
means the hold TIP102 transistor for that flipper is bad, or the
hold winding on the coil itself is broken. The hold winding on the
coil is the thin wire. If it is broken, usually the wire has
broken away from one of the solder lugs (the middle lug should
have both the thick and thin wire attached to it). Test the coil
first (see above) before replacing the transistor.
- Flipper coil gets really hot after playing the game for a
while. This is often a dirty flipper optic on the flipper board
next to the flipper buttons. It could also be a bad LM339 chip at
U4 and/or U6 on the Fliptronics board (or U25/U26 on a WPC-95 CPU
board). An easy way to see if it's the LM339 chip or the optics is
to swap the two flipper optic boards, and see if the problem
changes to the other flipper. A dirty flipper switch "U" optic can
essentially cause the flipper button to automatically turn on and
off quickly (even when the player is not pressing the button),
making the flipper coil warm.
- Flipper seems to work fine, but gets very hot and eventually
starts to burn and smell. Often the flipper will get stuck in the
"up" position. On fliptronic games, the hold TIP102 transistor for
that flipper is shorted on, and needs to be replaced.
- When a game is started, all the flippers activate for a
moment, then go dead. This can be caused by having the flipper
switch board connectors removed from the Fliptronics board. With
the connector removed, the game thinks all the flipper buttons are
pressed. The flippers go dead because the secondary 50 volt power
fuse blows.
- The flipper stays up for a moment after the flipper button is
released. This happens on fliptronic games that have plastic
activators which activate the flipper board optos. Sometimes the
plastic's elasticity is lost, causing it not to spring back
quickly when the button is released. Replace this plastic flipper
activator. A temporary solution is to stretch a rubber band across
the back of the plastic activator for additional tension. Flipper
opto boards were implemented on Addams Family, mid-production
(some Addams have them, some don't).
- Flippers work fine, but the flipper buttons do not work in
video mode or high score entry mode. On games with flipper optic
switch boards, there are two "U" shaped optic on each board. Games
with 2 or 3 flippers often use one of the two "U" optics for the
flippers, and the other for video mode and high score entry. This
problem could be caused by this second "U" optic being bad, dirty,
or there is a problem with the plastic activator not clearing the
second "U" optic.
If one or both flippers are weak...
Non-Fliptronics Games:
- Rebuild
the flippers. Play and wear in the flipper parts is the
primary reason for weak flippers. A mushroomed flipper plunger
dragging against the coil sleeve is a classic cause of weak
flippers.
- Make sure there is about 1/16" up and down play on the
flipper. To test this, from the top of the playfield, grab the
plastic flipper and pull up. There should be some play. If not,
the flipper could be binding on the nylon playfield insert. This
gap is adjustable from under the playfield by changing the flipper
pawl's grip on the flipper shaft.
- Make sure the EOS (end of stroke) switch is properly adjusted.
On non-fliptronics games, the EOS switch should open no more than
1/16" to 1/8" at the end of the flipper stroke. If the EOS switch
is misadjusted, this can cause a slightly weaker flipper on old
and new WPC games.
- On non-fliptronics games, file clean the EOS switch contacts
and the cabinet flipper switches. These are high-voltage tungsten
switch contacts, and a metal file will be needed to clean them.
These switch contacts often become pitted and tarnished, and
resistance develops, weakening flippers.
- Check the flipper power connections. On non-fliptronics games,
this is connectors J109 and J110 on the power driver board. Make
sure the solder joints on these board header pins are not cracked,
and that the connector and header pins are in good shape.
- Check the bridge and capacitor that supplies voltage for all
coils (BR3 and C8). An open diode in the bridge rectifier that
supplies power to the flippers can cause weak flippers. A fatigued
or cracked solder joint on this bridge (or its associated
capacitor) can do that too. Soldering jumper wires from the bridge
to its associated capacitor is a good idea. This is rare, but does
happen. This problem will effect BOTH flippers equally. See the
section, Testing
Bridge Rectifiers for more information.
Fliptronics
Games:
- Rebuild
the flippers. Play and wear in the flipper parts is the
primary reason for weak flippers. A mushroomed flipper plunger
dragging against the coil sleeve is a classic cause of weak
flippers.
- Make sure there is about 1/16" up and down play on the
flipper. To test this, from the top of the playfield, grab the
plastic flipper and pull up. There should be some play. If not,
the flipper could be binding on the nylon playfield insert. This
gap is adjustable from under the playfield by changing the flipper
pawl's grip on the flipper shaft.
- Make sure the EOS (end of stroke) switch is properly adjusted.
On games with electronic flippers (fliptronics), the EOS switch
should close right at the end of stroke, and not prematurely. If
the EOS switch is misadjusted, this can cause a slightly weaker
flipper on old and new WPC games.
- On WPC fliptronics and later games, try cleaning the "U"
shaped optics on the cabinet flipper opto boards. Use a Q-tip and
some Windex to clean them. Also make sure the opto activator bars
fully clear the optos when the cabinet switch is pressed. If one
weak flipper still exists, try swapping the cabinet flipper opto
boards (remember, both flipper boards must be plugged in for this
to work!). If the weak flipper problem moves to the other flipper,
the opto board's optic has become faulty, and it will need to be
replaced with a new "U" shaped optic. A marginal cabinet flipper
board optic, even if clean, can cause a weak flipper. Replace if
in doubt. Also check the opto switch with your multimeter. With
the game on and your meter set to DC volts, on the flipper opto
board measure the connector pin marked SW1 and SW2 against ground.
A measure of below 0.7 volts (below 1V is OK) should be shown,
with the button pressed. A higher reading means a dirty or
defective opto switch. If cleaning does not remedy the problem,
replace the opto switch. NOTE Later WPC-95 pinballs use a Schmitt
Trigger opto switch (3 legs on the receiver, 2 on the transmitter)
which eliminates this problem. The Schmitt trigger optos will not
oscillate (turn on and off quickly, making the flipper weak) when
the optics gets dirty. They usually either work, or don't work.
- On WPC fliptronics to WPC-S, replace the U4 and/or U6 LM339
chips on the Fliptronics board. On WPC-95 games, replace U25
and/or U26 on the CPU board (since these games don't have
fliptronics boards). Although these don't fail often, then can
cause weak flippers. See "WPC
Fliptronics Flipper Optos" in the switch matrix section for
more details.
- Check the flipper power connections. On WPC fliptronics to
WPC-S games, this is connector J907 and J902 on the fliptronics
board. On WPC-95 this is connectors J119 and J120 on the power
driver board. Make sure the solder joints on these board header
pins are not cracked, and that the connector and header pins are
in good shape.
- On WPC fliptronics to WPC-S games, check the fliptronics board
bridge rectifier (BR1). On non-fliptronics games, check the bridge
and capacitor that supplies voltage for all coils (BR3 and C8). An
open diode in the bridge rectifier that supplies power to the
flippers can cause weak flippers. A fatigued or cracked solder
joint on this bridge (or its associated capacitor) can do that
too. Soldering jumper wires from the bridge to its associated
capacitor is a good idea. This is rare, but does happen. This
problem will effect BOTH flippers equally. See the section, Testing
Bridge Rectifiers for more information.
While playing a game, a flipper gets weaker and
weaker. The longer the machine is left on, whether playing or not,
the flipper will still get weaker until it won't work at all...
Fliptronics Games:
- Dirty optic switches on the flipper board can cause this. Try
cleaning them with Windex and a Q-tip.
- Failing optic switches on the flipper optic board can cause
this too. Try swapping the left and right flipper boards. See if
the problem switches to the other flipper. Remember, both flipper
boards must be plugged in for this to work!
- On WPC fliptronics to WPC-S games, failing LM339 voltage
comparators at U4 and/or U6 on the fliptronics board. On WPC-95
games, replace U25 and/or U26 on the CPU board (since these games
don't have fliptronics boards). Although these don't fail often,
they can cause weak flippers. Do this as a last resort. See "WPC
Fliptronics Flipper Optos" in the switch matrix section for
more details.
Flipper coil gets very hot...
Non-Fliptronics Games:
- Check the EOS switch to make sure it is adjusted properly, and
that the contacts are clean and filed. The EOS switch should open
1/16" to 1/8" when the flipper is fully extended (on
non-fliptronics games).
Fliptronics Games:
- On WPC fliptronics and later games, if there is a marginal
flipper switch reading, this causes the high powered side of the
flipper to rapidly oscillate between on and off. The holding side
of the flipper coil never engages. This problem will cause the
flipper coil to get very hot in a short time. First try cleaning
the flipper board optics. If this doesn't work, the LM339's on the
Fliptronics board at U4 and/or U6 (or CPU board on WPC-95 at U25
and/or U26) will need to be replaced.
- Bad regulation of the 12 volt power to the optos can cause the
flipper coils to get hot too. Though rare, the 7812 voltage
regulator on the power driver board could be failing, or the
electrolytic filter capacitor for the 12 volts.
Flipper gets stuck in the up position... If the
flipper is stuck in the up position, turn the game off. If the flipper
falls back, the problem is electrical. If the flipper stays up, the
problem is mechanical.
Flipper problems should be addressed by at least one of the
above.
3f. When things don't work: the Lamp Matrix
Lights controlled by the CPU (not the General Illumination
lights), are controlled in a similar fashion as a switch matrix. That
is, there are eight lamp rows, and eight lamp columns. This gives a
total of 64 CPU controllable lamps. These lamps are powered by +18
volts DC. This voltage is strobed (turned on and off very quickly),
and hence the final power to the lamps is about 6 volts.
The lamp columns are controlled by TIP107 transistors that switch
the +18 volts on and off many times within a second. The lamp rows are
controlled by TIP102 transistors that switch the ground on and off.
Because the TIP107's source the current (instead of sinking the ground
like a TIP102), lamp column TIP107 transistors go bad more often than
TIP102 lamp row transistors.
Non-Working Lamps. If certain individual lamps do not
work (but others do, indicating the lamp matrix is functioning), there
are several things to check. If the lamp is mounted in a standard
socket, these sockets can become "loose" and go bad. A "loose" socket
allows air (and moisture) to get between the parts, causing corrosion.
Also the wires going to lamp socket are "daisy chained" from other
sockets. Did a lamp wire break "up stream"?
Circuit board mounted lamps have different problems. The most
common is cracked header pins on lamp circuit board. The connector
header pins soldered to the lamp's circuit board can crack right at
the board. Resoldering the header pins can fix this. Also the diodes
can break on the circuit board. For circuit board mounted 555 lamps,
this can happen due to vibration. This will make the lamp not
function. Finally, check the IDC (Insulation Displacement Connector)
on the lamp circuit board. These can have problems too.
Overly Bright Lamps. When a transistor or diode goes bad,
generally it shorts on. If a transistor shorts on in the lamp matrix,
it can make all the lamps in that row or column appear permanently on,
and be very bright. It can also make lamps that flash on and off
appear brighter too. This happens because the lamp matrix is actually
+18 volts that is continually turned on and off, a row or column at a
time. This nets a lower +6 volts that the lamps require. The lamps are
never allowed to get full brightness at +18 volts before being
switched off. If a transistor has shorted on, a row or column of lamps
will be turned on for a longer time, and hence be brighter.
All the computer controlled lamps in the lamp matrix should flash
in attract mode, or in the "All Lamps Test" diagnostic test. If a
number of lamps are just on (and they aren't general illumination
lamps), there may be a lamp matrix transistor problem.
If a number of lamps are out, check the bulbs and fuses first. If a
number of lamps are stuck on, check the game manual and see if they
are in the same row or column. If so, test the individual transistor
(see the Testing
Transistors and Coils section) before replacing it.
No Lamp Matrix Lights Work, or are Confused. If none of
the lamp matrix lights are working, the obvious thing to check is the
fuse. If the +18 volts is missing, none of the lamp matrix lights will
work and the 18 volt LED will not be lit. This is powered through
bridge BR1, fuse F114, LED6, and test point TP8 (on WPC-95 games
diodes D11-D14, fuse F106, LED102, and TP102).
What if the fuse is good (which would indicate the bridge/diodes
are good), the LED is lit, and the test point shows 18 volts DC? Yet
the lamp matrix lights don't work, or are "confused"? With the power
off, reseat the short ribbon cable that goes between the CPU and
driver board (this will clean the connectors on this ribbon cable).
Often this simple approach will solve the problem.
Lamp Matrix Fuse Keeps Failing (F114 or F106 on
WPC-95). If the lamp matrix 18 volt fuse keeps blowing (F114 or
F106 on WPC-95), isolate the lamp matrix power from the rest of the
game. This will determine if there is just a simple short or bad diode
on the playfield, or if there is a bad rectifying bridge or diode on
the power driver board.
On WPC-S and earlier, remove connectors J133-J138. On WPC-95,
remove connectors J121-J126. Replace the blown fuse, and power the
game on. If the fuse blows, the problem is probably a bad bridge BR-1
(WPC-S and prior) or bad diode D11-D14 (WPC-95). See the Game Resets
(Bridge Rectifiers, Diodes and Caps) section of this document for
testing or replacement.
If the fuse does not blow with the game powered on, replace the
removed connectors one at a time. When the fuse blows, you have
issolated the problem to the connector just installed. Most likely
there is a playfield lamp socket shorted. Or if new bulbs were just
installed, there may be a new bulb that is shorted (yes this does
happen). Either way, the wires from the connector just installed can
be traced, and the short located.
Left: #44/47 lamp, socket and the orientation of
the diode. Note the banded end of the diode goes to the
"middle" lamp lug. The non-banded end goes to the lamp's tip
lug. Right: The playfield socket used for 555 lamps. The
small metal tabs on the outside of the socket often get bent.
This prevents a good connection to the board on which they
plug. Bend them back for better contact.
|
|
Left: the component (lamp) side of a lamp board.
Note the 1N4004 diodes mounted to the board, and the use of
555 bulbs. The diodes can crack if soldered too tightly to the
board, causing the bulb to not work. Right: the solder
(socket) side of a lamp board. Note the Molex header pins
soldered here. Often these Molex pin solder joints crack or
become fatiqued, preventing the lamp(s) from
working.
|
|
Testing a
diode on a lamp socket circuit board. The black lead is on the
banded side of the diode.
|
|
Lamp Diodes (Lamps that don't work or work
"twice"). Each CPU controlled lamp will have a diode associated
with it. If this diode is bad (shorted on), it will cause other lamps
in that row or column (or even another row or column) to turn on. This
can usually be seen in the "All Lamps Test". The faulty row or column
will light *twice* in a single lamp matrix sweep (once when it should
be on, and a second time due to the short on *another* row or column
re-lighting it). The lamp(s) in question are on twice as long as all
the other CPU controlled lamps.
Another way to test this is to use the "Single Lamp" test. If two
different lamps are on for a single lamp test, there may be a short, a
bad diode, or a bad transistor.
If a lamp diode has broken (become open), or is disconnected from
the lamp socket, its lamp will not light. Broken diodes can happen on
circuit board mounted lamps (555 style bulbs). If the diode was
inserted and soldered into the circuit board "tightly", the diode can
crack due to mechanical stress and vibration. During the soldering
process, the diode body can elongate slightly. When it cools, the
diode shrinks back, adding more stress. If there's no other place for
that stress to be dissipated, the diode body is the weakest link, and
it can crack.
Two Lamps On Instead of One. If a lamp diode is shorted
on (or installed incorrectly), a bad TIP107/TIP102 transistor, or just
a short on the playfield lamp matrix, can cause two lamps to act as
one. This can be seen in the "Single Lamp Test". Each individual lamp
in the lamp matrix (as displayed on the screen) should flash. The "+"
and "-" buttons will move the test from one lamp to another. If TWO
lamps flash in this test instead of just one, suspect this lamp has
having a bad or mis-installed lamp diode, or it's associated
TIP107/TIP102 transistors as bad, or just a short between two row or
column wires.
It is pretty easy to tell which problem it is. First reference the
game manual, and figure out which rows/columns are the problem. To do
this, note all the lamps that "double light", and see what row/column
they occupy. A pattern should be seen, with the double lights being
all in the same row or column. As shown in the previously mentioned Transistor
Testing section, test the related TIP107 and TIP102 transistors
(as indicated in the manual for the related rows/columns) for a
problem.
If that checks out OK, next look for a short and/ or bad lamp diode
on the playfield. This is easy to test; just remove the lamp matrix
plugs from the power driver board (these connections are shown a few
paragraphs below). Using the DMM set to ohms, see if the associated
row/column wires are shorted to each other on the disconnected lamp
matrix plugs (not on the driver board!). If two lines buzz out with
zero ohms, there is a short or bad diode on the playfield somewhere.
Shorts happen often from solder drips when someone resolders a coil
under the playfield. These solder drips often land on the lamp boards
under the playfield, on the header pins, shorting two together.
Testing a Lamp Diode. In order to test a lamp diode, use
the DMM set to diode test. Put the black test lead on the banded side
of the diode. A reading of .4 to .6 volts should be indicated. Reverse
the leads and put the red lead on the banded side of the diode. A null
reading should be shown. Any other reading and this lamp's 1N4004
diode should be replaced. The light bulb doesn't need to be removed,
nor does the diode need to be desoldered to perform this test. Also
test the diode soldered to the circuit boards that hold the 555 lamps
in the same manner (but remove the connector and the 555 lamp before
testing).
Common Connectors. There are several lamp matrix
connectors which are common on the power driver board. Here are the
breakdowns:
WPC and WPC-S
- J133, J134, J135 = Lamp Rows (all wired identical)
- J137, J138 (large plug), J136 (small 3 pin plug) = Lamp Columns
(J137, J138 wired identical)
WPC-95
- J124, J125, J126 = Lamp Rows (all wired identical)
- J121, J123 (large plug), J122 (small 3 pin plug) = Lamp Columns
(J121, J123 wired identical)
With this in mind, on a WPC-95 game for example, connectors at J124
and J125 and J126 can be mixed up, because they are plug compatiable.
Testing the
lamp matrix rows using two test leads, a 555 socket
(pulled temporarily from the playfield), and a 1N4004 diode on
a WPC-95 game. One test lead is attached to column connector
J121 pin 1 (J137 on WPC-S and prior) on the driver board, and
is stationary. The other end is attached to the light socket.
Another test lead is connected to the second lead of the lamp
socket. A diode is clamped into the other end of the test
lead. Then the banded side of the diode is touched to
each pin of row connector J124 (J133 on WPC-S and prior). The
"all lamps" test should flash the lamp for each
pin.
|
|
Testing the Lamp Rows. If a TIP102 transistor that drives
a lamp row is suspected as bad, test it:
- Remove the backglass and fold down the display to gain access to
the Driver board.
- Turn the game on.
- After the game boots, press the "Begin Test" button in the front
door. Go to the Test menu's "All Lamp Test" test.
- Unplug the row connectors at J133 (or J124 on WPC-95) and column
connector at J137 (or J121 on WPC-95). These are on the lower right
portion of the Driver board.
- Connect an alligator test lead to column connector pin 1 of J137
(or J124 on WPC-95). Pin 1 is the right most pin, as facing the
board.
- Connect the other end of this test lead to one lead of a 555
light socket. One can be temporarily borrowed from a playfield lamp
(make sure it's a working lamp first!).
- Connect another test lead to the second lead of the 555 light
socket.
- On the other end of the test lead, clip on a 1N4004 diode, with
the non-banded end away from the alligator lead.
- Touch the non-banded end of the diode to row connector J133 (or
J124 on WPC-95) pin 1. Again, pin 1 is the right most pin, as facing
the board.
- The lamp should flash.
- Move the diode/alligator lead on row connector J133 (or J124 on
WPC-95) to the next pin. Again, the lamp should flash.
- Repeat the previous step, until the last pin of row connector
J133 (or J124 on WPC-95) is reached.
If a lamp row tested doesn't give a flashing test lamp, that row is
bad (or the test diode is reversed!). No light or a non-flashing,
bright lamp are signs that the respective TIP102 row transistor is
bad. Test the transistor as described in Testing
Transistors and Coils.
Testing the
lamp matrix columns using two test leads, a 555 socket
(pulled temporarily from the playfield), and a 1N4004 diode on
a WPC-95 game. One test lead is attached to row connector J124
pin 1 (J133 on WPC-S and prior) on the driver board, and is
stationary. The other end is attached to the light socket.
Another test lead is connected to the second lead of the lamp
socket. A diode is clamped into the other end of the test
lead. Then the non-banded side of the diode is touched
to each pin of column connector J121 (J137 on WPC-S and
prior). The "all lamps" test should flash the lamp for each
pin.
|
|
Testing the Lamp Columns. If a TIP107 transistor that
drives a lamp column is suspected as bad, test it:
- Remove the backglass and fold down the display, to gain access
to the Driver board.
- Turn the game on.
- After the game boots, press the "Begin Test" button in the front
door. Go to the Test menu's "All Lamp Test" test.
- Unplug the row connectors at J133 (or J124 on WPC-95) and column
connector at J137 (or J121 on WPC-95). These are on the lower right
portion of the Driver board.
- Connect an alligator test lead to row connector pin 1 of J133
(or J121 on WPC-95). Pin 1 is the right most pin, as facing the
board.
- Connect the other end of this test lead to one lead of a 555
light socket. One can be temporarily borrowed from a playfield lamp
(make sure the lamp works first!).
- Connect another test lead to the second lead of the 555 light
socket.
- On the other end of the test lead, clip on a 1N4004 diode, with
the banded end away from the alligator lead.
- Touch the banded end of the diode to column connector J137 (or
J121 on WPC-95) pin 1. Again, pin 1 is the right most pin, as facing
the board.
- The lamp should flash.
- Move the diode/alligator lead on column connector J137 (or J121
on WPC-95) to the next pin. Again, the lamp should flash.
- Repeat the previous step, until the last pin of column connector
J137 (or J121 on WPC-95) is reached.
If a lamp column tested doesn't give a flashing test lamp, that
column is bad (or the test diode is reversed!). No light or a
non-flashing, bright lamp are signs that the respective column TIP107
transistor is bad. Test the transistor as described in Testing
Transistors and Coils.
Most Common Problems with Lamps.
- Bad bulb. Any light bulb can burn out. Often it can visually be
seen the bulb is burnt, but sometimes it can't. Test the bulb with
the DMM, set to continuity. Put the test leads on the bulb. No
continuity, and the bulb is bad.
- Wire broken away from the socket. This happens quite often and
requires re-soldering the wire back to the socket lug. On lamp
sockets, wires are "daisy chained" from other sockets. Did a wire
break "up stream" in the chain?
- Cracked header pins on circuit board mounted lamps. The
connector header pins soldered to the lamp's circuit board can
crack. Resoldering the header pins can fix this.
- Diode broken away from the socket. If the lamp diode becomes
disconnected from its socket, the lamp will not light.
- Diode broken on the circuit board. For circuit board mounted 555
lamps, the diode can fail due to vibration. This will make the lamp
not function.
- Corroded or Bad Socket. Re-seating the bulb in its socket can
sometimes fix this problem, but often replacing the socket is the
only choice. On 555 plug-in sockets, bend the contact tabs slightly
for better contact.
- Blown Fuse. If several lights don't work, check the fuse
associated with them.
- Burned Connector on the Driver board. This happens most often
with GI (general illumination) lamps. See Burnt GI
Connectors for more info.
- Bad Column Transistor. The TIP107 transistors that control the
lamp matrix columns often fail. If this is the case, all the lamps
in a particular column will be brightly locked on, or can turn on
and off much brighter than other lamps.
- Two Lamps act as One. If a lamp diode has a shorted on, this can
cause two different lamps to act as one. A bad TIP107 transistor can
cause this too.
Burnt +18 Volt BR1 Bridge or WPC-95 Diodes D11-D14. This
problem is strange, but a lot more common than one might think. The
+18 volt (lamp columns) bridge or WPC-95 diodes get excessively hot
and burns. I've seen this where the driver board is black from the
heat. This happens because the lamp matrix is demanding more power
than the circuit is designed to handle. Eventually the associated fuse
F114 or F106 (WPC-95) will blow. Note the BR1 bridge or WPC-95 diodes
D11-D14 are probably OK. If these were bad, the fuse F114 or F106
(WPC-95) would blow immediately.
The reason for the burned bridge or diodes is simple; for some
reason, one (or more!) of the lamp columns is stuck "on". Remember,
the lamp matrix uses 12 volts, but this is derived by strobing
(turning on and off very quickly) 18 volts. If a column locks on,
instead of getting 12 volts, the full 18 volts is delivered. This
added voltage puts stress on the lamp column circuit, and causes the
+18 volt BR1 bridge or WPC-95 diodes D11 to D14 to get really hot (and
their associated fuse to eventually blow). To fix this, first check
all the TIP107 column driver transistors (see the Checking
Transistors section). Also see the next section too, on problems
other than the transistors.
All the Lamp Transistors are Good, so What's Next? If
none of the lamp matrix transistors have failed, then next suspect the
ULN2803 (U19 or U11 on WPC-95), or maybe the 74LS374 (U18 or U10 on
WPC-95). If the TIP107 transistors are OK, the ULN2803 is probably the
culprit. An easy way to tell if the lamp matrix has a problem is to
notice the controlled lamps right when the game is turned on. If any
playfield lamps flash on right at power-on (and the lamp matrix
transistors are good), there may be a problem with the ULN2803 driver
chip.
If the lamp matrix still does not work, the next thing to check are
the LM339 chips at U15/U16 (or U16/U17 on WPC-95). If one of these
LM339 chips are bad, part of the lamp matrix will not work. If the
entire lamp matrix is not working, also check resistors
R150-R153/R172-R173 (or R225, R228, R231, R234, R237, R240 on WPC-95)
for proper ground, as one side of all these resistors are tied to
ground. Likewise, capacitors C13-C20 (or C32-C39 on WPC-95) are also
tied to ground.
3g. When things don't work: the Switch
Matrix
When a switch closes, it informs the CPU to score points, award a
feature, and/or to activate a solenoid. If a switch is stuck closed
for a coil (such as a pop bumper switch), the CPU will ignore this
switch. Therefore the pop bumper will not work.
If a switch is not activated in 30 games, or is permanently closed,
the switch is assumed to be bad. This will create a test report, which
is shown when the game is turned on or when the coin door test button
is pushed. If a particular feature of a game is difficult to score,
it's associated switch may be (falsely) assumed bad (if not activated
in 30 games). To correct the test report, remove the playfield glass,
and activate the switch by hand within a game, or within the
diagnostics switch edge test.
All switches on a WPC game (except for the direct switches, which
includes flipper, EOS, and test button switches) are in the "switch
matrix". The switch matrix on a WPC game is controlled by eight switch
columns, and eight switch rows. the cross-section of any row and
column designates any one of the potential 64 different switches.
The Chips that Control the Switch Matrix. The switch
columns are controlled by a single 18 pin ULN2803 chip on the CPU
board at position U20. The switch rows are controlled by two LM339
chips on the CPU board at positions U18 and U19. The direct switch
rows are controlled by two LM339 chips on the CPU board at positiion
U16 and U17. These chip designations apply to all WPC generations.
On WPC-S and WPC-95 games, the ULN2803 that controls the switch
columns on the CPU board is socketed. On all other WPC games up to
1994 this chip is not socketed. When a series of switches goes out, it
tends to be the ULN2803 at U20 (all WPC revisions) that fails.
Williams recognized this, and started socketing this chip with WPC-S.
On WPC-S CPU boards, the ULN2803 chip is underneath the battery
sub-board. ULN2803 is equivalent to NTE2018. If U20 dies "hard", it
could also blow the 74LS374 at U14 (on WPC-95 it's U23, a 74HC237) on
the CPU board.
The LM339 chips that control the switch rows at U18 and U19 (all
WPC revisions) tend to fail less often. LM339 is equivalent to NTE834.
There are also two more LM339 CPU board chips at U16 and U17 (all WPC
revisions). These two chips control the direct switches (coin door,
diagnostics, etc). These do not fail often either.
There are also LM339 chips used on the under-the-playfield optic
board (if the game has one). If any one of these LM339 chips fail
(common), the switch matrix will be confused. When there is a switch
problem that can not be diagnosed, replace all the LM339 chips on the
under-the-playfield optic board, and use sockets.
The Switch Matrix Power Fuse. If fuse F115 (WPC-S or
earlier) or fuse F101 (WPC-95) opens (blows), the switch matrix will
not work (and hence none of the playfield switches will work). This
fuse supplies the +12 volts needed to operate the switch matrix.
Check TP3 on the Driver board for +12 volts. Using the
DMM multi-meter set to DC volts, check for +12 volts at TP3 (test
point 3) on the driver board (while the game is on). If +12 volts
isn't there, the switch matrix will never work. Also check for +12
volts at the "+" lead of bridge rectifier BR1 (the "indented" lead of
the bridge) on the driver board (WPC-S and before). Occassionally the
solder joints on this bridge will fail, therefore not providing +12
volts to the switch matrix (see the "Game Resets" section of this
document, and solder jumper wires under the board as shown in that
section).
How does the Game know the Switch Matrix doesn't
work? There is ONE switch in all WPC games called "always
closed" (always switch 24 on all WPC games). This switch is monitored
by the CPU board. If it sees this switch as open, the game knows there
is a switch matrix problem (perhaps no +12 volts!). Also if the
connectors are not attached on the CPU board at J206, J207, J208 and
J209, the CPU board can be confused about switch 24. For example, if
fuse F115 (or F101 on WPC-95) was blown, removing these connectors for
testing purposes, the game will probably give an error until the fuse
is replaced AND the connectors put back on. These connectors may have
to be removed to determine if the switch problem was on the CPU board
or in the playfield wiring. (The easiest way to determine this is to
disconnect all four switch matrix playfield plugs from the bottom
right of the CPU board {connectors J206-J209}. If the error goes away,
there is a playfield short. If the error stays, there is a problem on
the CPU board.)
Shorting the Switch Matrix to +50 volts. When in a hurry,
the repair person may make an under playfield adjustment with the game
turned on. If the coin door is closed, or the game doesn't have a coin
door interlock switch, it is easy to short a coil lead (+50 volts) to
a switch lead with a screwdriver. This will immediately blow the
switch matrix power fuse (F115 on WPC-S or earlier, or F101 on
WPC-95), and fry the ULN2803 at U20 on the CPU board. There is a good
chance the 74LS374 at U14 (on WPC-95 it's U23, a 74HC237) will fail
too on the CPU board. On WPC-S or later games, the U20 chip is
socketed (but not the U14, or U23 on WPC-95).
After Replacing CPU Chip U20, the Fuse does not Blow, but Many
Switches show in the Test Report. This is very common. The CPU
is confused from the blown U20 switch matrix chip, and will report
many switches as "bad" in the test report. To "unconfuse" the game, go
into diagnostic, and select the first switch test (T.1, switch edges).
Using a pinball, manually activate the switches that came up in the
test report (see the game manual for their location, if they can't be
found). The switches should report correctly on the display in this
test mode. After activating each switch once, exit the diagnostics,
and the game should work normally. Alternatively, if the game will
allow it, just play a game! This is often all that is needed to clear
the test report.
Still Switch Matrix Problems after Replacing U20. There
can still be problems after replacing the fuse and U20 and U14/U23 CPU
chips. For example, activating a switch in a column will trigger other
switches in that same column.
At this point, disconnect all four switch input plugs from the
bottom of the CPU board. Put the game into switch diagnostic test T.1,
and none of the switches should be activated! If a whole row of
switches is activated, that would mean that row's LM339 is bad. If
just one or two switches are activated, plug the four bottom
connectors back in and disconnect the ribbon cable that goes between
the CPU and the power driver board. If the switch matrix confusion
clears up, the problem in on the power driver board! This could be U7
and/or U8 (WPC-S and prior) on the driver board, which are 4N25 opto
issolators used for some of the direct switches.
There are also LM339 chips used on the under-the-playfield optic
board (if the game has one). If any one of these LM339 chips fail
(common), the switch matrix will be confused. When there is a switch
problem that can not be diagnosed, replace all the LM339 chips on the
under-the-playfield optic board, and use sockets.
I replaced F115 (or F101 on WPC-95), and the Fuse keeps
Blowing. If the switch matrix +12 volt fuse (F115 or F101 on
WPC-95) keeps blowing immediately when replaced, check these things
out.
With the game off, replace fuse F115 (or F101), and remove
connector J114 (or J101 on WPC-95) from the power driver board. Turn
the game on (the game will complain when powered on, but don't worry
about that).
If the switch matrix fuse F115 (or F101) does blow with
connector J114 (or J101 on WPC-95) removed, then there is a problem on
the CPU board. This usually means the CPU board chip U20 (ULN2803A) is
probably blown. Replace U20 (use a socket!), and reconnect J114 (or
J101), and the problem should be solved. Sometimes U14 on the CPU
board (U23 on WPC-95) will also need to be replaced. See the section
on fuses
for more information on what other problems can cause this fuse to
blow.
If the switch matrix fuse F115 (or F101) does not blow (and
the +12 volt LED is lit on the power driver board), then there
probably is a short somewhere in the playfield wiring or on an opto
board under the playfield. The opto boards under the playfield have
large blue resistors, and one to four LM339 chips. By disconnecting
the power to this opto board (there is a red LED on these boards
showing power) and turning the game on with connector J114/J101
connected, the opto board can eliminated or be the culprit (if fuse
F115/F101 blows).
If the problem is still present, Check for solder splashes and
maybe a nut/bolt that has fallen somewhere and has caused a playfield
short. Shorts on the playfield are quite common. Somewhere, the 20
volt lamp matrix or flashlamp circuit is getting shorted to the switch
matrix. Or the 50 volt solenoid voltage is getting shorted to the
switch matrix. Look under the playfield for lamp and solenoid wire
lugs that are close to switch lugs. The problem could also be on the
top of the playfield. Perhaps a errant pinball knocked a lamp socket
into a switch lug, causing a permanent or intermittent short.
If nothing can be found, here is a techinque to help find which
switch is shorted:
- After replacing the U20 on the CPU board with a socket, remove
the ULN2803 chip.
- Turn the game on. With the CPU chip U20 removed, the game will
complain with test reports, but ignore it.
- Using a DMM, set the meter to DC volts.
- Put the black lead of the DMM on ground (the side rail of the
game works well for this).
- Put the red lead of the DMM on pin 1 of the empty U20 socket.
- If the DMM reads anything over ~13 volts (for example 18 or even
70 volts), there is a permanent short for that switch matrix column.
Check all eight playfield switches in that switch column for a
short.
- Repeat steps 5 and 6 for all pins on the U20 socket.
- If no voltage over 13 volts is found, put the red lead of the
DMM back on CPU socket U20 pin 1.
- Press each playfield the switches on the playfield. If the DMM
reads anything over ~13 volts (for example 18 or even 70 volts),
check that target for a physical short to another voltage (flash
lamp power, solenoid power, etc.)
- Repeat steps 8 and 9 for all the pins of socket U20 on the CPU
board, by depressing each playfield switch.
Switch Numbering. Each switch has a number associated
with it. This number is referenced in the game manual, and is shown in
the diagnostics in the switch edge test. The switch number is always
two digits: the first digit is the switch matrix column number, and
the second digit is the switch matrix row number. For example, switch
number "42" is the cross section of column 4, row 2. This is handy
when trying to figure out if bad switches are all in the same row or
column.
Both
internal switch tests use this matrix to show which switches are
activated. The two outside columns of dots are the direct
ground switches; the left most dot column being the coin door
switches, and the right most dot column being the flipper
switches. The dots inside the square box are the 8 by 8 switch
matrix. A square represents an activated switch, a dot means a
non-activated switch. Notice the right most column inside the box
is missing; this game doesn't use a switch matrix column 8, as
it was not needed. Also the display shows the wire colors
(WHT-BRN and GRN-BRN) going to the last activated switch. The
"T.2" means this is test menu option #2.
|
|
Using the Internal Switch Tests. To test switches, use
the WPC internal test software. Press the "Begin Test" button, and go
to the Test menu. Select the "switch edge" test. Activate any switch
on the playfield using a pinball (this simulates real game
play), and it should show on the game's display. The display will
indicate the wire colors going to this switch, too.
Check for Broken Switch Wires "Up Stream" (Switches are "Daisy
Chained"). Since the switch matrix is a series of eight columns
and eight rows, the playfield switch wiring is "daisy chained". For
example, check out a switch matrix row in the manual. For row one, the
playfield switch in column three row one (switch 31) is wired before
the playfield switch in column four row one (switch 41). So if the row
one wire breaks off switch 31, all the switches "down stream" (41, 51,
61, 71, 81) will not work! This is one of the simpliest, and easily
overlooked, switch matrix problems.
Another hint that the there is a switch matrix wire broken; If for
any particular column and row other switches work, this indicates
there probably is not a problem on the CPU board! If there was a
column/row problem on the CPU board, it would most likely affect all
the switches in that column or row.
Broken switch wires can also occur at the CPU connector too. Make
sure to look at the connectors. The wires can fatique and break at the
connector, inside the insulation!
If a Bad Switch is Found. If a switch does not work,
check these things:
- Check the switch wiring "up stream". Switches are wired in a
"daisy chain". If a switch row or column wire breaks "up stream",
ALL the switches daisy chained after the wire break in that row or
column will not work!
- If it's a micro-switch, check the actuator arm. Make sure it's
adjusted properly. Listen for the micro-switch's "click" when
activating. No click usually means the switch is mis-adjusted or
broken.
- Check that the wires going to the switch are soldered well, and
haven't fallen off.
- Check the continuity (using the DMM's continuity setting) of the
wire between this switch and another working switch in the same
column (white wire) or row (green wire).
- If it's a blade or leaf style switch, check the contacts for
proper closure. Clean the switch contacts with a business card (do
NOT use a file as the contacts are gold plated). Put the card
between the contacts, close the contacts, and pull the card through
the contacts. This is all that is needed to clean gold plated switch
contacts.
- Check the switch to make sure it works. Use the DMM's continuity
setting, and put one lead on the "common" lug (the lug to which the
banded end of the diode connects) of the switch. Put the other lead
on the green (normally open) switch lug. The meter should only beep
when the switch is activated, and not beep when the switch is
de-activated. Move the DMM's lead from the green to the white wire
(normally closed) switch lug. The meter should beep when the switch
is de-activiated, and NOT beep when activated.
- Check the diode on the switch. Make sure the diode is connected
properly, and is working (see below).
- Check other switches in that switch's row or column. A ULN2803
controls columns and a LM339 controls rows, and often a gate within
these chip can fail. This will affect all the switches in that
particular row or column.
If the switch is bad, replace it. If all the switches are bad in a
particular switch column, replace the ULN2803 on the CPU board at U20.
If all the switches in a row are bad, replace the LM339 at U18 or U19.
Slam Tilt Stuck Open error. Upon turning the game on, a
"slam tilt stuck open" error is shown, and the game just won't do
anything past that. This can be as simple as the slam switch inside
the coin door is bent closed. Or it could be some sort of CPU switch
problem.
To issolate the problem, turn the game off and disconnect all the
connectors from the bottom of the CPU board. Then turn the game back
on. If the error is no longer shown, the problem is in the playfield
or cabinet wiring/switches. If the error is still shown, the problem
is in the CPU board itself. If the problem is on the CPU board,
usually it's a problem with a ULN2803 or LM339 chip.
Upper Flipper Switch Bad, but my game doesn't have an Upper
Flipper! On Williams games that use flipper opto switch boards
(Addams Family and later), the flipper opto boards have TWO switch
optics. One optic controls the lower flipper, and the other controls
the upper flipper. The same opto board is used on all games, even if
the game has no upper flippers.
Unfortunately, on some games, the software can create a switch
error "test report", if the game thinks the upper flipper board optic
switch is bad (even if the game has no upper flippers, and is not
using the switch). If the problem is really bothersome, the opto can
be replaced. But often, the problem is mearly the metal or plastic
flipper opto interuptor (the passes between the "U" of the opto
switch) is never moving outside the "U". By bending the activator to
clear the optic's "U", often this error message can be cleared.
Phantom Switch Closures: a Shorted Switch. It's a strange
problem. While playing a game, the ball goes down the right inlane,
and the left slingshot fires! Or when making a ramp shot, the game
slam tilts. One switch closes, but a completely unrelated event than
occurs.
This is a classic problem of a shorted switch. It confuses the
switch matrix into thinking something else has occurred. This can
happen from an "air" pinball, that bashes an above playfield switch's
contacts together, causing a short. Also a bad switch diode can do
this too. In either case, the shorted switch needs to be found.
Unfortunately, it won't be obvious. The switch matrix is confused, so
any diagnostics the game provides will be of limited help.
First, try and find the "phantom" switch (the switch that causes
something unrelated to happen). Take the playfield glass off, and
start a game. Activate the switches with your hand, and find the
phantom switch. Once the switch is found, go to the game manual and
find the switch's number, row number, and column number. Say for
example, switch 53 (column 5, row 3) is causing the phantom closure.
Now get the other three switches that make up the "square" of this row
and column. First get the reverse switch number, switch 35 (column 3,
row 5). Then get the other two switches: switch 33 (column 3, row 3),
and switch 55 (column 5, row 5). The switch short will probably be one
of these four switches.
The 10 opto
switch driver board as used in Indiana Jones and many other
games. The three IC's are LM339 chips. The power plug for this
board is on the left, next to the row of diodes. This
board is mounted under the playfield.
|
|
Phantom Switches and Opto Switches. If one of the
phantom switches is an optic switch, there may be a problem with the
under-the-playfield optic board. Williams also used optic light
emitting diodes (LED's) for switches. These are controlled by
sub-boards (opto driver boards), mounted under the playfield, which
interpret the light signals and converts them to digital signals. This
is done using LM339 chips on the opto driver board. If a LM339 goes
bad, it will give the CPU board bad switch signals. This is
interpretted as a bad switch column or row, when in fact, it's really
a bad opto driver board. This can make an optic or non-optic switch
row or column act wacky.
If there are phantom switches, the first and easiest thing to try
is to disconnect the power to the under-the-playfield optic board.
When the power plug is disconnected (usually the plug nearest the row
of diodes) from the optic board (you can do this with the game on),
the LED soldered to the optic board will turn off. Now re-test the
switches. If the problem has changed, there is a bad optic board! If
the problem has not changed, plug the optic board back in and move on.
If the optic board is at fault, replace ALL the LM339 chips on this
board (there are usually two or three of them). These chips can not be
tested easily. It is just easier to replace them all (use sockets!).
Some games (Shadow) with lots of optics can use a "opto24" board.
This board can control up to 24 optics! Again, this is done using
LM339 chips. In addition to this, there is also a 555 timer chip on
the opto24 board. This too can fail, causing intermittent opto switch
problems.
Bad Switch Diode. Each micro-switch on the playfield also
has an 1N4004 diode soldered to it. This diode can short closed. It
doesn't happen often though. Important: If a switch diode does
short closed, all switches in that particular column or row will
exhibit strange behavior. If a switch diode goes permanently open, the
switch will never register. Keep this in mind when diagnosing switch
matrix problems.
Fail-Safe Diode Test. A fail-safe way to test a switch
diode is to disconnect one lead of the diode from the switch, to
remove it from the circuit. Then use a DMM set to diode position. With
the black lead on the banded side of the diode, a reading of .4 to .6
volt should be shown. Reverse the leads, and get a null reading.
Reconnect the diode after testing, or replace if bad.
Testing a
switch diode on a microswitch without removing the diode. Not
the screw driver keeps the switch activated, and the middle
green wire (ground) has been disconnected.
|
|
Testing a Microswitch's Diode, without removal. The
diode on a microswitch can be tested without unsoldering a diode lead
from the switch. This technique assumes the switch is wired in the
standard configuration: green (ground) wire to the center lug, the
banded end of the diode to the far switch lug, and the non-banded
diode lead and the switch wire(s) to the close switch lug (as shown in
the pictures below).
- Disconnect the middle green (ground) wire from the switch. It
should have a quick connector. If the middle green ground wire is
soldered to the switch, ignore this test and do the above
"fail-safe" diode test.
- Put the DMM on diode setting.
- Connect the black lead of the DMM to the diode's banded side,
and the red lead to the non-banded side.
- Activate the switch.
- A reading of .4 to .6 should be shown on the meter.
- Reverse the DMM's leads (red lead to the diode's banded side),
and keep the switch activated. A null meter reading should be
indicated.
Testing a Blade/Leaf Switch's Diode. Testing the diode on
a leaf switch is far easier. No wires need to be disconnected, and the
switch should not be activated. This technique assumes the switch is
wired in the standard configuration: green (ground) wire to the center
lug, the banded end of the diode solo, and the non-banded diode lead
and the switch wire(s) to the other switch lug (as shown in the
pictures below).
- Leave the leaf switch's diode and all wires connected.
- Make sure the switch isn't activated.
- Put the DMM on diode setting.
- Connect the black lead of the DMM to the diode's banded side,
and the red lead to the non-banded side.
- A reading of .4 to .6 on the meter should be seen.
- Reverse the DMM's leads (red lead to the diode's banded side). A
null meter reading should be indicated.
Testing a
switch diode on a blade/leaf switch, without removing the
diode. The switch doesn't need to be activated, and no wires
need to be disconnected.
|
|
Installing a New Switch Diode. The diode can be replaced
with a new 1N4004 (or 1N4002 or 1N4001) diode. Make sure the new diode
is installed with its band in the same orientation as the old diode
(assuming it's correct!). If unsure, compare the diode's band
orientation to a working switch and diode. Most (but not all!)
switches have the green (column) leads connected to the center
(normally open) lead of the switch. Then the white (row) wire is
connected to the switch lead closest to the center lead (the normally
closed lead). The banded end of the diode is connected solo to the far
(common) switch leg, and the non-banded end is connected to the same
leg as the white (row) wire. There are some exceptions to this
mounting. The game manual should specify any non-standard switch
installations (Bride of Pinbot's zero position head switch is one such
exception).
Notice the
orientation of the diode's band on these switches. On a
micro-switch, the column (green) wire usually goes to the
center lug, the row (white) wire and the non-banded side of the
diode to the lug closest to the center. The band on the
diode goes to the solo, far third switch lug. The leaf switch
uses the same connection method (green to center, banded end
of diode solo). Note there are some exceptions to this
mounting.
|
|
Accidental Reversal of a MicroSwitch's Row and Column Leads
(mis-wired switch causes switch matrix havok!). If someone has
installed a new microswitch, the row and column leads could be
accidentally reversed to the switch. Say for example switch 48 is a
microswitch in the game, and has the row and column wires accidentally
reversed. The switch matrix will still reconized this switch (the
switch will seemingly work), but is registered as switch number 68,
not 48! This can be a hard problem to find, as the switch still seems
to work. Unless there is access to the game manual, and know that this
switch should be number 48 (and not number 68), the problem may not be
found!
If a switch is mis-wired, it can cause other problems too. Using
the internal wwitch test, often a single switch can show as multiple
switch closures (one switch shows two or more switches activated
during the switch test). Normally looking for crossed wires, bad
diodes, bad LM339 and ULN2803 chips on CPU or under-the-playfield
optic board would be the thing to do. But there can be another
(simple) cause too: a switch wired completely backward. This happens
often when someone changes a switch, and accidentally wires it
"backwards". Keep this in mind when diagnosing switch matrix problems.
Testing the
switch matrix columns: Using a diode and a test
lead, the test lead is attached to pin 1 of J209, and is
stationary. The other clip holds the non-banded side of the
diode. Then the banded side of the diode is touched to
each pin of connector J207. The "switch levels" test should
indicate switches 11 to 81 (by ten) when
activated.
|
|
Testing the Switch Columns (all WPC revisions). To test
the switch columns, do the following:
- Remove the backglass and fold down the display to gain access to
the CPU board.
- Turn the game on.
- After the game boots, press the "Begin Test" button in the front
door. Go to the Test menu's "Switch Levels" test.
- Unplug the connectors at J212, J206, J207, J208 and J209 (lower
portion of the CPU board).
- Connect an alligator test lead to pin 1 of J209. Pin 1 is the
right most pin, as facing the board.
- On the other end of the alligator test lead, clip on a 1N4004
diode, with the banded end away from the alligator lead. Touch the
banded end of the diode to pin 1 of J207. Again, pin 1 is the right
most pin, as facing the board.
- The display should show switch 11 is closed.
- Move the diode/alligator lead on J207 to the next pin. The
display should show switch 21 is closed.
- Repeat the previous step, until pin 9 of J207. Switches 11, 21,
31, 41, 51, 61, 71, 81 should be closed on the display as moving
forward, pin by pin, on connector J207.
Note: on some WPC games, columns 8 and/or 7 are not used.
In these cases, there may be no indicator for switches 81 and/or 71.
If a particular column does not display as closed, or is closed
without any test lead connection, replace the ULN2803 at U20 on the
CPU board.
Testing the
switch matrix rows: Using a diode and a test lead, the
test lead is attached to pin 1 of J207, and is stationary.
The other clip holds the banded side of the diode. Then the
non-banded side of the diode is touched to each pin of
connector J209. The "switch levels" test should indicate
switches 11 to 18 when activated.
|
|
Testing the Switch Rows (all WPC revisions). To test the
switch rows, do the following:
- Remove the backglass and fold down the display to gain access to
the CPU board.
- Turn the game on.
- After the game boots, press the "Begin Test" button in the front
door. Go to the Test menu's "Switch Levels" test.
- Unplug the connectors at J212, J206, J207, J208 and J209 (lower
portion of the CPU board).
- Connect an alligator test lead to pin 1 of J207. Pin 1 is the
right most pin, as facing the board.
- On the other end of the alligator test lead, clip on a 1N4004
diode, with the non-banded end away from the alligator lead. Touch
the non-banded end of the diode to pin 1 of J209. Again, pin 1 is
the right most pin, as facing the board.
- The display should show switch 11 is closed.
- Move the diode/alligator lead on J209 to the next pin. The
display should show switch 12 is closed.
- Repeat the previous step, until pin 9 of J209. Switches 11
through 18 should be closed on the display as moving forward, pin by
pin, on connector J209.
If a particular row does not display as closed, or is closed
without any test lead connection, replace its corresponding LM339 chip
on the CPU board. Here are the switch rows and which LM339 controls
them:
- Rows 1,2,3,4 = U18
- Rows 5,6,7,8 = U19
Testing the Switch Matrix Columns and Rows with a Logic
Probe. If a logic probe is available, the switch matrix can be
easily tested:
- Remove the backglass and fold down the display to gain access to
the CPU board.
- Turn the game on.
- After the game boots, press the "Begin Test" button in the front
door. Go to the Test menu's "Switch Levels" test.
- Unplug the connectors at J212, J206, J207, J208 and J209 (lower
portion of the CPU board).
- With the logic probe connected to power and ground, probe each
pin 1 to pin 9 of J207 (pin 1 is the right most pin, as facing the
board). These are the switch columns. All pins should show PULSE on
the logic probe. If no pulsing activity is shown, the ULN2803 at U20
is bad.
- With the logic probe connected to power and ground, probe each
pin 1 to pin 9 of J209 (pin 1 is the right most pin, as facing the
board). These are the switch rows. All pins should show HIGH on the
logic probe. If a pin is not high, its corresponding LM339 on the
CPU board is bad (rows 1,2,3,4 is U18, rows 5,6,7,8 is U19)
Switch matrix short: is it the CPU board or the
playfield? One of the diagnostic errors gotten from WPC games
often is "switch matrix row shorted". This can happen for a variety of
reasons (see below), but the big question is this: is the short on the
CPU board (a failed component like the LM339 at U18-U19 or the ULN2803
at U20), or on the playfield (where a switch may be physically
touching ground)? The easiest way to determine this is to disconnect
all four switch matrix playfield plugs from the bottom right of the
CPU board (connectors J206-J209). If the error goes away, there is a
playfield short. If the error stays, there is a problem on the CPU
board.
Further Diagnosing of the Switch Matrix. If there is a
switch matrix problem, the first plan of attack is to do the above
column and row switch matrix tests. If these tests pass, the problem
most likely is in the wiring. Note most switch failures show as Row
failures (even though it could be a column problem). Here are eight
different ways the switch matrix can fail. All require use of the
internal "switch level" or "switch edge" tests of the game.
- Switch column shorted to ground.
When a column wire is
shorted to ground, and any switch in that column is closed, the
switch test will show ALL switches in the ROW of the closed switch
as being closed. If no switches are closed, the switch test will
show no switches closed. To find the location of the short, go to
the end of the switch column wire on the playfield (the switches are
"daisy chained" together for an entire column or row). Then break
the daisy chain one switch at a time until the short no longer shows
in the switch test.
- Row shorted to ground (diode anode).
When the anode
(non-banded end of the switch diode) is shorted to ground, the
switch test will show the entire row as activated (whether any
switches are closed or not). To find the location of the short, go
to the end of the switch row wire on the playfield (the switches are
"daisy chained" together for an entire column or row). Then break
the daisy chain one switch at a time until the short no longer shows
in the switch test.
- Row shorted to ground (diode cathode).
When the
cathode (banded end of the switch diode) is shorted to ground, that
switch's entire row will show as closed in the switch test (whether
the switch is open or closed). To find the location of the short, go
to the end of the switch row wire on the playfield (the switches are
"daisy chained" together for an entire column or row). Then break
the daisy chain one switch at a time until the short no longer shows
in the switch test.
- Column wires shorted together.
When two column wires
are shorted together, and none of the switches in those columns are
closed, the switch test will show no problems. But pressing any
switch in either column will show that switch, along with a switch
in the column that is shorted on the row of the switch being closed.
For example, if column 2 and column 4 are shorted together, closing
switch column 2 row 3 will also show a closed switch in column 4 row
3.
- Row wires shorted together.
When two row wires are
shorted together, and no switches are closed, the switch test will
show no closed switches. When any switch in either row is closed,
another switch on the same column as the closed switch will also
show as closed. For example, if rows 1 and 4 are shorted, closing a
switch in row 1 column 3 will also show a closed switch on row 4
column 3.
- Column and row wires shorted together.
When a column
and row wire are shorted together, the switch test will show the
switch that is at the intersection of the row and column as being
closed, even though it is not closed. All other switches on all
other rows and columns will work correctly. For example, column 1
and row 3 are shorted together. The intersection of this column and
row will show that switch as closed (even though it's not). And
remember, this switch is not the cause of the problem!
- Open diode on a switch.
An open diode on a switch will
cause only that switch to not work.
- Shorted diode on a switch.
A shorted switch diode will
show no problems when only that switch is opened or closed. However
if additional switches in that row or other columns are closed,
false switch readings can be shown.
The Optic Switches are Going Crazy! The optic switches
are a bit more complicated than standard micro switches. All the
optics require +12 volts to operate. If this 12 volt supply gets
interrupted, has become intermittent, or drops to a lower voltage, the
switch matrix can go crazy. Sometimes this can be seen in the
diagnostic switch tests as optic switches that very quickly open and
close.
This can be caused by cold or cracked solder joints on the
connectors going to optic boards. While the game is in the switch test
mode, wiggle the wires and connectors on the opto driver boards under
the playfield. Also check the connectors at the power driver board
too.
Another problem can be cracked power solder joints on the power
driver board at capacitor C30 and bridge BR5 (WPC-S and prior), or
capacitor C8 and diodes D3, D4, D5, D6 (WPC-95). This happens much
more often on WPC-S and prior games though. Soldering jumper wires to
capacitor C30 (or C8 for WPC-95) can fix this problem.
If a large number of optics seem to be affected, it could also be a
CPU board problem. The U20 chip (ULN2803) on the CPU board may have
failed (this chip is socketed on WPC-S and later games). Or possibly
the +12 volt bridge and/or its associated capacitor on the power
driver board has a cracked solder pad, or the +12 volt bridge itself
could be bad.
Fliptronics Flipper Switches, EOS switches, and Test Button
Switches. On WPC-95 games, the flipper switches are wired
directly to the CPU board (on WPC-S and prior Fliptronics games, the
flippers are wired directly to the Fliptronics board). The test button
switches (inside the coin door) are also wired directly to the CPU
board on all WPC revision. These switches do not go through the
switch matrix on any WPC revision. The flippers and EOS switches (on
WPC-95), and test button switches (all WPC revisions) are part of set
of 8 direct switches to the CPU board, which go through two LM339
chips, at position U16 and U17.
On WPC-95, the EOS switches go to connector J208 on the CPU board,
and the flipper opto switches go to CPU connector J212. On pre WPC-95
games, the EOS switches go to the Fliptronics II board connector J906,
and the flipper opto switches go to Fliptronics II board connector
J905. The test switches on all WPC game revisions go to CPU board
connector J205.
On pre-Fliptronics games, the EOS switches and flipper switches are
NOT wired through any circuit board. They are wired directly to the
flippers themselves. The cabinet flipper switches and EOS switches
just complete the flipper power circuit to ground.
Switch Maintainence. Here are the procedures for
maintaining WPC switches:
- Micro-switch: no maintainence required. Can adjust the actuator
arm only by rotating the switch in its bracket. Do not BEND the
activator arm! Loosen the two screws holding the switch, and rotate
the switch to adjust the activator arm. Re-tighten the screws, but
not too tight as it will bind the switch mechanism.
- Blade or Leaf switch: clean with a business card inserted
between the contacts. Squeeze the contacts closed, and remove the
business card. Do not use a file on these gold plated contacts!
Re-adjust the contact spacing for correct operation.
- Opto switches: use a Q-Tip and some Windex. Dip the Q-tip in the
Windex, and clean the opto's two LED's (receiver and transmitter)
with the Q-tip.
End of WPC Repair document Part Two.
|