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.
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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://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: Stuck On Coils and Flashlamps (Checking
Transistors and Coils)
If a coil is "stuck on" when the game is turned on, a shorted driver transistor
is often the 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, and other related faults.
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.
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TIP102 transistors, the small 2N5401 pre-driver transistors,
and the coil diodes on the driver board.
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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
(and solenoids 29,31,33,35 on some games).
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
(and solenoids 30,32,34,36 on some games, and solenoids/flash lamps 37 to 44 on
Indiana Jones, Star Trek Next Gen, Demo Man, Roadshow and Twilight Zone).
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 and
used as a pre-driver on the Auxiliary driver board.
Games with Solenoid Numbers Above 28 (Auxiliary Driver Board).
Even though the WPC driver board only supports solenoids 1 to 28,
there can be solenoids numbered up to 44. Most often seen
are numbers 29 to 36, which use transistors in the fliptronics section
of the board. If the game only has two flippers, the fliptronics section
will have two flipper power (TIP36) and two flipper hold (TIP102) transistors that may be
used by the game for things other than flippers. Also several games (Indiana
Jones, Twilight Zone, Demo Man, Roadshow and Star Trek Next Gen) used an 8-driver
auxiliary driver board, which contained eight more TIP102 transistors for
even more flash lamps or coils. Note this board also contains circuitry for
an extra ninth switch matrix column (used on STNG, Twilight, Indy Jones only).
This auxiliary driver board could be problematic, especially on Star Trek Next Gen. On Star
Trek, this board needs +50 volts for a "tieback diode" voltage for the circuit (because
it controls solenoids, and not just flashlamps; all the other games that use this
Auxiliary driver board only control flashlamps). The 50 volt tieback power is connected by
a thin violet/yellow wire which connects to the playfield's single drop target coil (at the
back of the playfield), and goes to the Auxilary Driver Board.
If this wire breaks, or if some other power wire in this coil power
daisy chain breaks, it can cause the two under-playfield
diverter coils to lock on (after they're first
activated in game play!) If the problem is not found quickly, the diverter coils and their
driving transistors can fail. Transistors on the auxiliary driver board will short
out in a couple of activations on Star Trek if the tieback voltage is not present
on the board. If the two Star Trek diverter coils lock on after a game is started,
check the violet/yellow wire which connects to the playfield's single drop target coil.
Additionally, add 1N4004 diodes to the two diverter coils (banded side of the
diode to the coil's power lug), and test the TIP102 transistors on the Auxiliary
driver board.
If a transistor shorts on the Auxiliary driver board, this will cause the driving
coil to lock-on as soon as the game is turned on. Again on STNG this is very common
for the under-playfield diverter coils. With the game off, check the diverter coils first -
they should have 7 to 9 ohms of resistance (tested in-circuit, any less and replace the coil).
Then go to the manual and figure out which Auxiliary driver board
transistor drives the coil in question. Don't bother testing the transistor(s) on
the Auxiliary driver board. They will *not* test correctly in-circuit. Just replace
the TIP102 and it's companion 2N4403. Replace *both* transistors at the same time!
Do not skimp here, or you will have to replace both transistors again after the
game is turned on! Also test all the resistors related to these two transistors,
and the 1N4004 diode (the diode and resistors can be tested in-circuit). Buzz
out all traces related to the two transistors also, especially the 50 volt tie-back
trace.
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?
A short summary (before reading all the info below).
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).
Also remember to test the resistance of a coil after replacing
the driver transistors. If a coil gets hot, it can burn the painted
enamel insulation off the coil windings. This lowers the overall resistance
of the coil because adjacent windings short together.
If resistance gets much below 3 ohms, the coil becomes
a "short", and will fry its associated driver transistors very quickly!
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).
Checking for power at the coil first. Use a DMD set to DC volts, one DMD lead
on either coil lug, the other DMD lead to ground (the metal side side rail
on the game is a good ground). Around 20 to 75 volts DC should be seen. Now
switch to the other lug of the coil, and the same voltage should be seen.
If there is no power at either coil lug, check the game's fuses. Also remember
power is "daisy chained" from other coil(s). Perhaps the power chain is broken
"upstream" from a broken wire (it is easy to manually trace the power
wire from coil to coil). If power is only seen at one lug of the coil,
the coil itself is bad, usually from a broken winding. Often it is the
winding that attaches to the coil's solder lug. Sometimes the broken wire
can be unwound one winding, sanded (to remove the painted-on enamel insulation),
and resoldered to the coil lug. Note intermittent coils can have a broken
coil winding that makes the coil sometimes work (or not work!)
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.
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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 one at a time. 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 one at a time. 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 one at a time.
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 one at a time. 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.
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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 wound coil wire before re-soldering, otherwise there
will be no connectivity.
- Make sure there is power at the coil. Using a DMM, there should
be 20 to 75 volts DC on either lug of a coil. If there is power only
on one lug, the coil winding is broken, and the coil should be replaced.
- 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".
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Flipper coil wiring. Note the wire color rules
specified below are the "usual" wire colors (but can't
be 100% guarenteed).
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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.
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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.
Test the Coil Resistance with a DMM.
After replacing the driver transistor, ALWAYS measure the resistance
of the associated coil. This is important.
If a coil gets hot (becuase its driver transistor was shorted),
it can burn the painted
enamel insulation off the coil windings. This lowers the overall resistance
of the coil because adjacent windings short together.
If resistance gets much below 3 ohms, the coil becomes
a "short", and will fry its associated driver transistors very quickly!
To test the coil's resistance, it is best to remove the attached wire
from one (either one) of the coil's lugs. Then set the DMM to low
resistance, and put the DMM leads on the lugs of the coil. Most coils should
be in the 5 to 15 ohm range, but could go as high as 150 ohms, or as low
as 3 ohms. If the coil is much below 3 ohms, it should be replaced with
a new coil of the same type. Coils with resistance much below 3 ohms are
basically a dead short, and this will fry its associated driver transistor.
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.
- Reset the driver board and CPU board ribbon cables. I have seen
situations where a coil hasn't worked because the gold plated ribbon
cable connectors were dirty.
3d. When things don't work: Game Resets (Bridge Rectifiers and Diodes)
What is a Reset?
Game resets are probably the biggest problem with 1990 to 1995 WPC to WPC-S games
(and to a much 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 4.7 volts (from heavy voltage draw when the 50 volt flippers are used),
the "watchdog" circuit chip on the CPU board
resets the CPU, momentarily shutting the game down.
The high current draw flippers stresses the
5 volt power components in the system. If these 5 volt 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. (When things are really bad, sometimes the game won't
even power-up, as it gets into a loop of turning itself off and on.)
Why are Resets so Common on WPC and WPC-S games?
I get this question a lot. "Why don't I have this reset problem on my
Williams System11 games?" When WPC was designed they decided to use a
voltage watchdog device, which was not implemented on earlier board designs.
This 3-legged transistor-looking MC34064 device is on the CPU board
at U10. (With pin1=output reset voltage, pin2=input supply voltage, pin3=gnd,
and could be replaced with a TO-92 case
Dallas DS1811-10
with a 4.35 volt reset, but not suggested.)
Williams did this to "micro-manage" the voltage to the CPU board. The new
parts implemented on WPC (ASIC chip, which replaced the six PIA chips on system11), requires
a consistent 5 volt power source. Their fear was without a solid 5 volt power source,
sparatic behavior could result, causing game and coil lock ups. Of course the
downside to this is, as WPC games get older, reset problems become
much more common.
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 115 to 120 volts AC present! If there is only 112 volts,
this can cause the game to reset. Some games, like Twilight Zone, will
often reset if the wall voltage is below 117 volts.
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 (air conditioner,
refrigerator, etc).
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. Also don't have the
game plugged into the same circuit as another power sucking device
(like a dehumidifier, sump pump, air conditioner, refrigerator, etc.)
If the problem is persistent, the game can be re-jumpered for
low-line voltage, or the driver board modified
to bump up the 5 volt power to 5.1 volts (this is described at the end
of this section, and really are 'last resort' things).
Check the Driver Board Voltages.
Next make sure the voltages at the driver board are Ok. Of course
this assumes the wall voltage is Ok (if the wall voltage is low,
any unregulated voltage will certainly be low, and often regulated
voltages will be low too). Here's what
to check ("TP" means Test Point, which are test points on the driver
board). Check these voltages with the game on, and in "attract" mode.
Remember there is more information on voltages in
part one
of this document.
- +5 volts DC: TP2 (TP101 on WPC95). Should be 4.92 to 5.1 volts DC.
If this is below 4.92 volts, the game will most certainly reset easily,
as this is the voltage the "reset watchdog" examines.
Often the problem is bridge rectifier BR2 (diodes D7-D10 on WPC95)
and the related filter capacitor C5 (C9 on WPC95).
Sometimes it could also be the +5 volt voltage regulator is failing
(Q1 LM323K or LM317 on WPC95). Or it's very common for the input connector (J101/J129)
or 5 volt to CPU board output connector (J114/J101) on the driver board.
Remove driver board +5/12 volt connectors J114 (power to CPU board), J116 (cabinet),
J117 (backbox), J118 (playfield), and measure the 5 volts at TP2 on
the driver board (on WPC95 connectors J101, J139, J138, J140/J141 respectively).
If you still below 4.92 volts, change the LM323K regulator.
If the +5 volts goes up with these four connectors removed, one of the
other boards/devices is dragging the +5 volts down. Replace the connectors
one at a time to try and find the culprit.
- +18 volts DC (lamp matrix): TP8 (TP102 on WPC95).
This is an unregulated voltage, so it can vary from 16 to 20 volts.
If this is low, check bridge BR1 and capacitor C6/C7 (diodes D11-D14 and caps C11/C12
on WPC95).
- +12 volts DC regulated: TP3 (TP100 on WPC95).
Should be 11 to 13 volts DC. This voltage comes from the +18 volts
lamp matrix (discussed above), and goes through a 12 volt regulator (7812) and
some 1N4004 diodes and an LM339 chip. If the +18 volts is
correct at TP8 (TP102 on WPC95), but this voltage is low,
it is usually the 7812 voltage regulator at Q2 has failed.
If any of the above voltages are low, resets will usually occur.
But just because the above voltages are Ok, does *not* mean the
game won't reset. Remember, the above voltages are being tested in
attract mode, and not under stress.
Now it's time to check some more voltages, but under stress.
This is a bit more difficult to do, but here is the procedure.
Use a non-autoranging DMM (or set your auto ranging DMM to non-autorange).
Or use a scope.
- Check TP2 (+5 volts DC) on the power board. Try and get the game to
reset and see if the +5 volts dips during the reset.
There should be no change in the +5 volts, even during a reset.
- Check TP4 on the power driver board, which is the
zero cross signal. Again it should look steady with no changes even during a reset.
- On the CPU board check U10 pin 1 (the reset pin on the MC34064).
This pin may dip low during reset, forcing a game reset when the flipper buttons are pressed.
The U10 is the watchdog circuit, and when it's reset pin 1 goes below
4.7 volts, the MC34064 forces the CPU to reset and reboot. You can follow the voltage
trail back from the MC34064 and try and figure out the exact component causing
the problem. Remember if during the process a reset connector fixes the problem,
this connector must be replaced (both header pins and terminal pins) to fully
fix the problem.
But why is the voltage on U10 pin 1 dipping below 4.7 volts?
There are a number of things that can cause this, as discussed here.
Check the Connectors (J101/J129, J102/J128, and Transformer).
First connector to check is input power J101 (J129 on WPC995)
on the power driver board. This provide AC power from the transformer
to the power driver board, which ultimately ends up as +5 volts DC, 18 volts DC
unregulated, and +12 volts DC regulated (via bridge rectifier BR1 & BR2, some
filter caps, and some voltage regulator circuits). If this connector is damaged
in any way, this can cause the voltages discussed above to be low, and resets
to occur. Try a simple reset. If a "dark" game now boots or resets go
away, replace the connector pins with Trifurcon style .156" pins, and
replace the driver board pins with new .156" header pins.
Also check the connector that takes power out of the driver board and
to the CPU board. This is connector J114 on WPC/WPC-S, or connector J101 on WPC-95.
Now try re-seating the connectors
on the large transformer in the bottom of the cabinet. 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.
Another bad connector could be J102 (J128 on WPC95) on the power driver
board, 16 volts AC. Though less likely to be a problem, reseat it
and see if resets change.
Also check J112 (J127 on WPC-95), as this provides power from
the transformer too (9.8 volts AC).
If the reset problem changes after reseating a connector, you have a TEMPORARY
fix! Yes I did say temporary, as chances are excellent the reset
problem will come back. The connector pins really need to be
replaced to permanently fix this problem The only way to fix this properly
is to replace (at minimum) the connector housing
terminal pins (with Trifurcon pins), and the circuit board header pins
(but at dead minimum replace the terminal pins with Trifurcons).
It is very common for these connectors
to have bad pins or cracked solder joints, especially on Twilight Zone.
Due to vibration and age, these connectors can just plain fail, and have
some internal resistance. Again use Trifurcon style pins, which grab
the male connector pin on three sides (thus giving better contact
and vibration resistance.)
Disconnect the Dot Matrix Display.
A failing dot matrix display can consumes more power, and can drive down
the other voltages in the game, causing resets. To make sure the display
is not causing resets, disconnect the power connector from the dot matrix
display glass (*not* the ribbon cable!) Then turn the game on and play (blind,
no display), and see if the game still resets. If it no longer resets,
the dot matrix display and/or the high voltage power section on the
DMD controller board will need to be replaced.
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. The
flipper problems section of this
manual shows how the flipper diodes should be installed. Check for
broken/cracked diodes, and replace them with new 1N4004 diodes if in doubt.
Biggest Game Reset Culprits: Bridge Rectifier (or WPC-95 Diodes),
Filter Cap, Cracked Solder Pads, and bad J101/J129 connector.
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 rectifier (or diodes) and its filter capacitor and
J101/J129 connector are over stressed and need replacement.
On WPC-S and prior games, a bad BR2 bridge rectifier,
its associated C5/C4 filter capacitor, and marginal terminal pins
on connector J101 are
probably the most commonly failed components relating to game resets.
As a general rule, if the wall voltage is good (above 116 volts)
these three things are what I replace first when there is a
reset problem. I replace ALL FOUR ITEMS (BR2 bridge, C5 cap, C4 cap, J101 terminal pins)
at the same time. Again this is my first line of attack when repairing
reset problems, and 95% of the time it works. On WPC-95 resets are
less common but the diodes D7,D8,D9,D10 and filter cap C9/C1 and
connector J129 are what I replace.
Also very common on WPC-S and prior games
are cracked solder pads on the bridge rectifier and/or
associated filter capacitor, which also causes game resets.
Always run jumper wires between the BR2 bridge rectifier
and the C5 filter cap when I replace them (solder side of board,
top right BR2 "+" lead to top C5 "+" lead, and diagonal BR2 "-" lead
to bottom C5 "-" lead). And I always check the
continuity between the new BR2 bridge rectifier's AC leads
and the zero cross diodes
(component side lower left AC BR2 board pad to the right side of D3 and
the upper right BR2 AC lead to the right side of D38).
Warning: when replacing a bridge rectifier it is VERY easy
to damage the circuit board. The bridge has four rather thick legs soldered
through the board. If they are incorrectly heated as they are removed,
it can pull the "plated-thru holes" out of the circuit board. This will
compromise the connectivity between the bridge and the board, causing
further reset problems. To avoid this, CUT the old bridge out first, leaving
the legs as long as possible. Now heat each leg individually, and pull
them out of the board with needlenose pliers, one at a time. Removing a bridge this way
should minimize damage to the board.
Testing Bridges.
Also keep in mind that just because a bridge rectifier tests as "good", does
*not* mean it is good. After all, a bridge can not be easily tested
when the game is in multi-ball, with the flippers flipping, and the
pop bumpers popping.
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".
When replacing bridge rectifier BR2, be careful not to tear or break the circuit
board traces at the bridge. Board damage here is very common because BR2 is
often replaced, and often in a hurry. Since a bridge rectifier is
a large part, vibration can crack the circuit board traces.
In particular notice the small trace on the component side of the driver board
under one of the bottom left AC leads of BR2.
This goes to the non-banded side of diode D3 (under connector J109) for the
zero cross circuit. If this trace is torn or cracked,
resets will likely still occur (more details/pics on that below).
After soldering in a new BR2, be sure check continuity on the board component side
from the lower left AC BR2 board pad to the right side of D3. Likewise
check the continuity from the upper right BR2 AC lead to the right side of D38
(or the solder side of the driver board from the upper left BR2 board pad
to the solder pad about 1" to the right).
Also it's a good idea to run jumpers from BR2 to its filter capacitor C5,
as described below, because the plated thru holes for the BR2 are damaged.
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.
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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.
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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.
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The Electrolytic Capacitors: 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).
A good replacement cap is available from Digikey,
Panasonic 15,000 mfd 25 volts, part number P6891-ND.
Also replace cap C4 (100 mfd 25 volts) with a 470mfd or 1000mfd cap.
Another potential electrolytic cap problem is at C4 on the driver
board (C1 on WPC-95). This 100mfd cap is a "keep alive" cap for the +5 volts, that
helps prevent the +5 from dropping when other parts of the power supply are
stressed, and helps stablizes the +5 a bit behind the LM323K.
Just like C5, the cap C4 also dries out and should be replaced too.
This 100mfd cap can be bumped up to 470mfd or even 1000mfd to help
prevent reset (but don't go any higher than 1000mfd, as this puts undo
stress on the LM323k voltage regulator).
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 capacitor
that fail the most, and cause the most reset problems. Also replace driver board
cap C4 with a 470mfd or 1000mfd cap.
- 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,
opto power, 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.
Note early versions of the Fliptronics II board had C2 installed, but later
versions did *not* use this capacitor, and it is missing from the board.
In any case, this capacitor is not needed, as the flipper coil 50 volts
does not really need to be filtered.
WPC-95 Driver Board:
- D3, D4, D5, D6 to C8 (10,000 mfd @ 35v) to F109: +12 volts unregulated for playfield devices,
opto power, 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 capacitor that fail the most, and cause the
most reset problems. Also replace C1 (100mfd 25 volts) with a 470mfd or 1000mfd version.
- 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 F107:
+20 volts for flash lamps.
- D19, D20, D21, D22 to C22 (100 mfd @ 100v) F108/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 black lead of the DMM on the "+" (positive) terminal of the bridge.
- Put the red lead of the DMM on either AC bridge terminal.
Between .4 and .6 volts should be seen. Switch the red DMM lead to the other AC
bridge terminal, and again .4 to .6 volts should be seen.
- Put the red lead of the DMM on the "-" (negative) terminal of the bridge.
- Put the black lead of the DMM on either AC bridge terminal.
Between .4 and .6 volts should be seen. Switch the black DMM lead to the other AC
bridge terminal, and again .4 to .6 volts should be seen.
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 Minor Load, In the Game.
This tip is from John Robertson.
This test is a more conclusive way to test a bridge (though a bridge that
tests good here can still cause game resets!) 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.
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- 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.
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- 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), or C4 cap (100 mfd 25 volt). But remember, a bridge that
tests good here can still cause game resets!
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.
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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). Also, if the game is
10 years old or more, I suggest replacing filter capacitor C5/C4
(C9/C1 on WPC95). If the game is still resetting (and the filter
cap was not replaced), definately go ahead and replace the associated
filter capacitors (C5/C4, or C9/C1 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 BR2 and/or BR1 on WPC-S and Prior:
Splitting the Large Heatsink.
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 may
need replacement shortly. If either BR1 or BR2
is bad, generally not a bad idea to replace 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 bridges are then screwed to the heat sink, and both bridges
re-installed (it is much easier to install the bridges if they
are both already screwed to the heat sink).
Also a lot of people cut the
heat sink in half when replacing BR2/BR1. This makes
replacing one bridge a lot easier. The theory is, the driver board's plated
through holes for these bridges take enough abuse, so doing any
unnecessary desoldering is a bad thing in my opinion.
Hence the heat sink is cut in half.
Note I do NOT recommend cutting the heat sink in half.
The reason has to do with physics. When the heat sink is
cut in half, it acts like a cantilever. This puts A LOT of
stress on the bridge's four solder points, and the circuit
board's plated-thru holes. Since pinball is a high vibration
environment, the cantilever effect can actually pull the
bridge out of the circuit board. But if the heat sink is
a single unit with eight solder points, the cantilever effect
is far reduced. This is why I do not recommend cutting the
BR1/BR2 heat sink in half.
Also there should be a thin layer of 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. A good brand of heat sink compound is "Arctic Alumina".
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 0.20 volts AC is seen, the capacitor is bad (actually many
people would say if more than 0.10 volts AC is seen the cap is bad).
The problem with this test is the leads for the
filter caps are nearly impossible to access when the driver board
is installed in the game. In the case of C5 (+5 volts with bridge BR2),
use an alligator jumper lead connected to the red DDM lead
to side of the "+" BR2 bridge rectifier, and the black DMM lead to ground.
Switch the DMM to low AC volts to measure the C5 capacitor ripple.
Note if the BR2 bridge is bad, excessive ripple will be seen.
For this reason, I usually just replace the filter caps in
question (C5/C4 or C9/C1 on WPC95) when replacing the BR2 bridge
or WPC95 +5 volts rectifiers.
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
(www.digikey.com or 800-344-4539)
or Mouser (www.mouser.com or 800-346-6873).
Don't get a cap that is too "tall", as it will stick out horizontally from the
driver board and increase stress on the cap's solder points.
- 15,000 mfd 25 volt, Digikey part# P6891-ND, Panasonic snap cap. An excellent replacement
in both quality and size.
- 15,000 mfd 25 volt, Mouser part# 5985-25V15000 or Digikey part# P6577-ND.
- 12,000 mfd 25 volt, Mouser part# 5985-25V12000 or Digikey part# P6575-ND.
- 10,000 mfd 25 volt, Mouser part# 5985-25V10000 or Digikey part# P6573-ND.
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 and plated through circuit board holes 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 and plated-through circuit board holes.
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. The plated-through
circuit board holes allow continuity from the solder side traces to the
component side traces. 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. It's the size and weight of
the bridge rectifiers and filter capacitors that causes this problem,
and heat just makes the problem worse. This can cause an intermittent
connection, or a higher resistance connection (cold solder joint).
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, especially if the
circuit board's plated-through hole traces are cracked (very common).
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.
WPC and WPC-S Driver Board Jumpers:
For reference, the driver board is positioned with the solder side showing,
and connector J104 at the "top". All jumpers added to the solder side of the
driver board.
- 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).
- C6: Add another jumper from the positive lead of C6 to TP8 (Test Point 8,
18 volt DC). Note this jumper is not shown in the picture below.
- 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.
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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.
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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 rectifying diodes on the driver board had a cracked solder pad. This
prevented the voltage from getting any further than it's
associated rectifying diodes (I should have known; the +20 volt
LED at TP104 on the Driver board was not lit!) Adding the
jumper wires from the diodes to the capacitor fixed the problem.
Remember, the purpose of the jumpers on a WPC95 driver board is
for added insurance on the *filter cap*. The diodes do *not* need
the jumpers (other than the filter cap connects to the diodes).
Its the weight of the filter cap is what causes the
solder pads to crack (from vibration). The diode's solder pads just don't crack.
WPC-95 Driver Board Jumpers.
At minimum, add jumper wires for the +5 volt filter capacitor
and rectifying diodes.
The other diodes and filter cap can be jumpered too, as desired:
- +5 volts: Jumper from the non-banded side of D7/D8 to the negative
lead of cap C9, and from the banded side of D9/D10 to the
positive lead of cap C9.
- 12 volts unregulated: Jumper from the non-banded side of D5/D3 to the negative
lead of cap C8, and from the banded side of D4/D6 to the
positive lead of cap C8.
- 12 volt regulated & 18 volt Lamp Matrix: Jumper from the
non-banded side of D11/D12 to the negative
lead of caps C11/C12, and from the banded side of D13/D14 to the
positive lead of caps C11/C12.
- 50 volt coils: Jumper from the non-banded side of D19/D22 to the negative
lead of cap C22, and from the banded side of D20/D21 to the
positive lead of cap C22.
- 20 volt coils: Jumper from the non-banded side of D16/D18 to the negative
lead of cap C10, and from the banded side of D15/D17 to the
positive lead of cap C10.
Replace the +5 Volt Filter Capacitor at C5/C4 (or C9/C1 on WPC-95).
If the game is still resetting, there's probably a good chance
that the +5 volt 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.
Any game that is 10 years old or more should have the +5 volt filter cap replaced.
Also replace driver board cap C4 (100 mfd 25 volts) or C1 (WPC-95) with a 470mfd or 1000mfd version.
Again Check the Power Driver Voltage Plugs (Transformer, J101/J129).
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
and connectors sections).
Any problems with the above mentioned connectors can cause
random game resets.
The Zero Cross Circuit and Resets on WPC-S and Prior.
The zero cross circuit serves a couple purposes, one of which
has to do with game resets. Part of the driver board's zero cross circuit are
diodes D3 and D38 (located just below connector J109),
which are both powered from driver board
AC power traces going to bridge rectifier BR2. Since BR2 is often a
replaced part, sometimes the traces going to D3/D38 get broken. This can cause
random game resets (it can also cause the General Illumination lights to not dim!)
So whenever replacing the bridge Rectifier BR2, be sure to use a DMM and
"buzz out" the two AC leads of the BR2 bridge, making sure they
go to non-banded side of diodes D3 and D38 (component side upper right BR2
lead to the right side of D38, component side bottom left BR2 lead to right
side of D3).
There is also a very easy way to make sure that the zero cross traces
from the AC leads of BR2 are not broken. Just power the game on and
go to the G.I. test menu. If the G.I. lamps do not dim (they are full
on regardless of the brightness level), then a circuit board trace
going to D3 and/or D38 is broken.
Component side of a WPC-S and prior driver board. Note the broken trace
(yellow circle) from BR2 to diode D3, which can be easily seen with BR2 removed.
If this trace is broken, the game will still ramdomly reset and the GI will
not dim.
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Solder side of a WPC-S and prior driver board. Note the trace (red circle) which
goes to diode D38, and is easily broken at BR2. If this trace is broken, the game
will not allow the GI lights to dim (GI only full on, or off, no in-between).
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Game is Still Resetting.
The 5 Volt Regulator and CPU board Chips.
The +5 volt regulator at U1 (LM323 on WPC-S and prior)
on the power driver board could be weak or bad.
This is a cheap and available part
(Radio Shack even sells them), so go ahead and replace it
(on WPC-95, the +5 volt regulator is again Q1, but it is a LM317k).
This +5 volt regulator does fail, and it's a smallish part, so
it would be the first thing to replace if everything else has been
checked or replaced.
Also the LM339 voltage comparator chip
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
(all WPC revisions). These chips connect directly to the CPU, and can have
heat problems that cause a game to reset.
Also I have seen problems with the CPU board's U8 (6264) RAM chip causing reset
problems. This is a static sensitive chip, so it is easily damaged.
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 Power Box and 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 moment, 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/caps),
limiting the in-rush current (and lengthening the life of the bridges)
by acting as a low value resistor.
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,
especially when the game is "cold".
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 (say one minute), no more
than 1.00 volts AC should be measured with a DMM across the Thermistor,
with the game in the attract mode (not playing). Note
when the game is first turned on, as much as 5 volts AC can be seen across
the Thermistor. But this voltage should drop down to under 1 volt AC as the game
warms up in the next minute. The thermistor is the gray disc device wired
from the line filter to the fuse.
The thermistor is an 8 amp, 2.5 ohm current limiter, and
can be purchased from Mouser Electronics (part number 527-CL30).
Do not confuse the thermistor with the
Varistor (MOV), which is the green disc wired across
the two AC lugs of the line filter.
Also be careful monkeying around inside the power box, on
do this with the game unplugged, as there is 115VAC (or 220VAC for Europe) present.
Also measure the thermistor with the game power off and "cold" using a DMM
set to ohms. No more than a 2 or 3 ohms should be seen. If any more than
that, replace it.
But the easiest way to determine if the thermistor is a problem
with game resets, is to jumper around it temporarily. Using an
aligator test lead, just jumper around the thermistor, and
power the game on and test for resets when the game is "cold".
No more resets means the thermistor is bad.
Note the thermistor was removed for many (but not all) WPC-95 games. It was
no longer needed as the bridge rectifiers were replaced with
discrete diodes, and the filter caps were changed from 15,000 mfd
to 10,000 mfd. So WPC-95 games may or may not have a thermistor installed.
The "power box" just inside the coin door.
Picture by John Robertson.
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Measuring the AC voltage across the Thermistor, with the game in
attract mode. No more than 1.00 volts AC should be seen.
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Connectors inside the Power Box.
While checking the thermistor and varistor, also check the single
spade lug connectors used on the power switch and the RF (Radio Frequency)
Filter. Sometimes these connectors can get loose and burn, causing
low power to the driver board, and game resets. Instead of installing
new connectors, just solder the wires directly to the power switch and
RF Filter, as shown below.
A power box where the power switch and RF filter connectors have been
removed, and the wires soldered directly (red circles). This was done because
the original spade lug connectors had burnt.
Pic by J.Robertson.
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Bad Line Fuse Holder.
Another not so common failure point is the main line fuse
for the game in the power box. This style of fuse holder is not
great quality, and can become "loose" and cause resets. Though
not common it can happen. Also the line fuse itself can have resistance
and lower the line voltage.
Power box where the power switch and RF filter reside, and the line fuse
holder is obviously having some problems (see the arcing burn marks on
the right side of the fuse holder). In this Twilight Zone replacing the
line fuse holder fixed the reset problems. The gray disc connected to
the line fuse is the Thermistor.
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Low Line Voltage Jumpers (105 Volts).
If the game is at a 120 volt location but has 112 volts or less at the
wall outlet and is resetting, the game can be jumpered for "low line voltage".
This is also known as the 105 volt Japanese voltage setting. I don't
recommend this if the voltage is above 112 volts as it does put stress
on the regulated voltage components on the driver board and possibly the transformer.
Please let me say that
again: DAMAGE can occur to your game if it is transformer jumpered incorrectly!
But it can be used in those rare situations where power is below 112 volts.
It involves rejumpering the .093" round Molex connector plugs at the transformer
(a .093" round Molex connector remover is required, available from
Waldom Electronics part# W-HT-2038 or Radio Shack part# 274-223 ($4.99).
Instead of the jumper going between pins 8 & 9 of this connector, they are
moved to pin 5 & 6. Below are pictures of this modification on pre-DCS WPC games.
ONLY DO THIS IF THE WALL VOLTAGE IS 112 VOLTS OR LESS.
The normal 120 volt transformer jumpers on an Addams Family.
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The low line 105 volt transformer jumpers on an Addams Family.
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The low line 105 volt transformer jumpers for WPC-S and later:
Pin 1 to 11, Pin 2 to 3, Pin 4 to 10, Pin 5 to 6.
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Still Reseting? Another Last Resort.
This bit of information is unique to this repair guide.
You probably won't hear about this stuff elsewhere. And
there may be a good reason for that. As this is the last reset
thing I can recommend. This is not a bad thing to do, but
I just think it's the absolute last thing you should try.
On WPC and WPC-S games, the 5 volt regulator is a LM323K.
These regulators have a working voltage range of 4.7 to 5.3 volts.
That's a big range, but unfortunately, that's how they work.
The problem is for a WPC game, anything below 4.9 volts and you
will have reset problems. Yes you can replace the LM323K, but
really, if you have 4.8 volts, the LM323k is working within spec.
And these LM323k regulators are becoming more expensive.
Though normally thought as a fixed voltage regulator, the LM323k
does have the ability to vary the output voltage. The metal
case of the LM323k goes directly to ground on the WPC and WPC-S driver board.
But if the LM323's metal case is isolated from ground, and then
connected to a 22 ohm 1/2 watt resistor (with the other end
of the resistor going to ground), this will increase the output
of the LM323k slightly. I found using a 22 ohm 1/2 watt resistor
will raise the output voltage to about 5.15 volts. This should fix
any persistant reset problems. (Note as the resistance is increased to say
33 ohms, 5.25 volts will result.) This option works GREAT in situations
where resets are a problem, and all the other options have been tried.
Modification to a WPC/WPC-S driver board to bump the 5 volts to 5.15 volts.
Here the BR2/C5 jumper wires are installed (red wires), and the blue circles
show the modifications to implement a 22 ohm resistor to the LM323 rectifier.
Note the ground trace is cut around the LM323k bolt, and ground is directed to
the bolt thru a 22 ohm 1/2 watt resistor. Also on some revisions of the WPC
driver board, the LM323 has a ground trace on the component side of the board
that will also need to be cut. Always buzz out the ground to the metal case of
The LM323 to ensure you have it isolated from ground when doing this mod.
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Component side of the driver board with the LM323k voltage regulator removed.
The blue line shows where the ground trace was cut to isolate the metal case of
the LM323k from ground. This mod is only needed on some revisions of the driver board.
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A similar modification can also be performed on a WPC-95 driver board.
In this case the 5 volt regulator is a LM317, which is an adjustable
output voltage regulator. Williams has the voltage set to 5 volts
using a 750 ohm 1/2 watt resistor at R1. If you change this R1 resistor
to 780 ohms, this will raise the LM317 output voltage to 5.2 volts.
Again this should cure any persistant reset problems.
The question may arise why any of this is needed. It turns out
the LM323 and LM317 do not have very tight manufacturer specs.
So the output voltage can vary greatly from regulator to regulator.
Also as components age in a game, they can consume more power.
Because of this you may find it necessary to do the above modification
to fix a persistant reset problem. I have found this modification
to work well on stubborn WPC games with four flippers, and in conditions
where the wall voltage is in the 110 to 115 range.
End of Reset Problems.
Other Misc. Bridge/Power Problems.
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
U14 (74LS374) on the CPU board. On WPC-95 and WPC-S it's U23 (74HC237 or
74HC4514 respectively).
- 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 C11 Capacitor (or C10 on WPC95).
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 on a WPC-S or earlier driver board,
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 or coil that 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.
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EOS Switches: Normally Closed or Normally Open?
Pre-fliptronics (non-computer controlled)
games have a high voltage, normally closed end-of-stroke
(EOS) switch. But Fliptronics flippers are basically an electronic CPU controlled (instead of
mechanical) version of the above explained non-fliptronics flippers. The main difference is
fliptronics CPU controlled 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 Coil Numbers and Strength.
If there are problems with fliptronics fuses and fliptronics
TIP36 and/or TIP102 transistors blowing, check the flipper coil resistance.
Resistance is shown below so a questionable flipper coil may be tested.
The upper measured ohms should be within 10% of the values below, and the
smaller measured ohms should be within 3%. To measure flipper coil resistance,
used a DMM with one lead on the center coil lug, and the other
DMM lead on either outside coil lug. The high powered side of the coil
is the low resistance. Note no WPC flipper coil should ever be lower
than 3.8 ohms! If it is, it will blow flipper fuses and could ruin
fliptronics driver transistor(s). Likewise the hold side of the flipper
coil should never be below 120 ohms, or again fuses can blow and
transistors may fail.
The flipper coils are listed below from weakest to strongest.
- FL-11753: used for small flippers, like the "Thing" flipper on
Addam's Family. 9.8 ohms/165 ohms. Usually a yellow coil wrapper.
- FL-11722: used for weak flippers, like Twilight Zone's upper
right flipper. 6.2 ohms/160 ohms. Usually a green coil wrapper.
- FL-11630: "standard" flipper strength, as used on older games
like Earthshaker, Whirlwind, etc. 4.7 ohms/160 ohms. Usually a red coil wrapper.
- FL-15411 : strong flipper, as used for main flippers on Addam's Family,
Twilight Zone, etc. 4.2 ohms/145 ohms. Usually an orange coil wrapper.
- FL-11629: strongest Williams flipper. Used on most of the newest WPC
games. 4.0 ohms/132 ohms. Usually a blue coil wrapper.
Flipper Diodes.
All WPC games will have two diodes attached at the flipper
coil lugs. 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".
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Fliptronics flipper coil wiring. Note the wire color rules
specified below are the "usual" wire colors (but can't be
100% guarenteed).
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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.
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Fliptronics versus "Classic Old Style" Flippers.
Starting with Addams Family in 1991, Williams changed from a conventional
"classic" flipper system (which had change very little from its invention in 1947), to
an electronic CPU controlled flipper system called "Fliptronics". The Fliptronics flippers
were now controlled by a circuit board mounted in the upper left corner of the backbox
(above the CPU board).
When the player pressed the cabinet flipper button,
the Fliptronics board would send 70 volts to the high-powered
side of the flipper coil (Fliptronics and non-Fliptronics parallel-wound
flipper coils are the same). Then the Fliptronics board looks for the
low voltage flipper EOS (End of Stroke) switch to *close* (where classic
old-style flippers had the EOS switch *open* when the flipper coil was energized). As soon it
sees this switch close, it diverts the 70 volts to the low-power side of the
flipper coil. This allows the player to hold the flipper cabinet switches in for
extended periods without burning the flipper coils. If the Fliptronics board
sees no EOS switch closure in a short period of time (the EOS switch is mis-adjusted
or broken), it still diverts power to the low-power side of the flipper coil,
preventing coil burn.
The advantage to this electronic system is the EOS switch can be broken, missing or
mis-adjusted and the flipper will work normally. That is, the flipper coil
will have normal power and won't burn if the player holds the cabinet
flipper buttons in. Essentially the EOS switches are redundant and not absolutely
needed. In older "classic" style flipper systems, a broken or mis-adjusted EOS
switch meant weak flippers, burnt flipper coils, or blow fuses. The fliptronics
system avoided this. It also allows the CPU board to control the flippers too,
allowing the game to flip for the player. This was used in games like Addams Family's
"thing flip" and Monster Bash's "phantom flip".
Another advantage to the Fliptronics system is it gave the game designers more
transistors for driving other coils. For example if the game only had two flippers
(Fliptronics boards could drive up to four flipper pairs), the Fliptronics board's
unused driver transistors could be used for other chores. This was
done on Theatre of Magic and Tales of the Arabian Nights (both two flipper games).
The game designers ran out of Driver board transistors, and used
the extra Fliptronics board drivers to control non-flipper coils.
Fliptronics I versus Fliptronics II.
The first Fliptronics system was used in Addams Family and is known as "Fliptronics_I".
This was the *only* game that used this sytle Fliptronics circuit board. All games
after Addams Family (including Addams Family Gold) use the "Fliptronics_II" circuit board.
The differences between these two boards is minor. The main difference is the
Fliptronics_II circuit board has an on-board 70 volt DC power supply for powering
the flipper coils. The Fliptronics_I
system uses a separate circuit board (mounted on the right middle side of the
backbox) for supplying the 70 volt DC flipper power.
Since the Fliptronics_I system was only used in Addams Family, many people look
for a spare Fliptronics_I circuit board (why I am not sure as this board
is easy to repair). The thinking being the Fliptronics_I board was only used in Addams
and is fairly rare and hard to find as a spare. The good news is that a
Fliptronics_II board *will* fit and work without any modifications in an
Addams Family (so there is no need to look for the rare Fliptronics_I board
as a spare, as any Fliptronics_II board will work in Addams Family).
Here is the connector mapping for the conversion from
Fliptronics-I to Fliptronics_II for the Addams Family (thanks to M.McAndrew for this info).
Note using a Fliptronic_II board in an Addams Family makes the game play *no* different
than the original Fliptronic_I board.
Using a Fliptronics_II board in an Addams Family:
- Fliptronics_II J902 = Fliptronics_I J802
- Fliptronics_II J905 = Fliptronics_I J805
- Fliptronics_II J906 = Fliptronics_I J806
- Fliptronics_II J904 = Fliptronics_I J804
- Fliptronics_II J903 = Fliptronics_I J803 (ribbon cable)
- Fliptronics_II connectors not used: J901, J907
Using a Fliptronics_II board in an Addams Family.
Power Driver board (only pertaining to flipper power section):
- J111 - Remove connector (disconnect) and do no use
- J112 - Leave connector
- J110 - Leave connector
- J109 - Leave connector
Using a Fliptronics_II board in an Addams Family.
Flipper Power Board board (small board, backbox middle right side):
- J901 - Leave connector
- J902 - Leave connector
- J903 - Leave connector
What If I Hook up a Flipper Coil Wrong in a Fliptronics Game?
If the wires are reversed or incorrectly attached to a flipper coil
on a fliptronics WPC game, damage will occur to the flipper coil
and the fliptronics board.
The first thing that happens is the flipper fuse will blow on the Fliptroncs board.
Turn the game off, and wire up the flipper coil correctly (see the
above information and pictures). Next replace BOTH 1n4004 diodes
on the flipper coil, and replace the blown fuse. You can try powering
up the game, but I would suspect the driving TIP36 transistor on
the fliptronics board will also be shorted. (This is easy to tell,
as the flipper coil will stay energize as soon as the game is powered up
or a game is started.) Also check all the 1n4004 diodes in that flipper circuit
on the Fliptronics board with a DMM. There is a good chance the
'hold' TIP102 and 2n4403 transistors may be bad too, which you can test with a DMM.
Lastly, check the traces on the back of the fliptronics board coming from
the top J902 connector. Often the hold traces will be burned right off
the board. (This happens because when the flipper coil is wired in reverse,
the hold circuit is now wired thru the high-current portion of the coil,
and the traces just burn like a fuse.)
Flipper Problem Troubleshooting.
If the flipper(s) don't work at all...
Non-Fliptronics Games:
- Check the flipper fuses on the driver board, fuses F101 and F102.
- Check for 50 to 75 volts at the flipper coil. Put a DMM on DC volts,
and the black lead on ground (metal side rail of game). Put the red
lead on any of the three lugs of the coil. It should be between
50 and 75 volts. No voltage means a fuse is blown, or a wire has
broken going to the coil. If voltage is missing from one of the coil
lugs, then the coil has a broken winding and should be replaced.
- Another way to test the flipper coil itself. To do this, turn your game on and
leave it in attract mode. 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 lug of the flipper coil.
The coil should activate.
- Also 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.
The outside lug with the banded side of the diode connected
has both the thick and thin wires connecting to it.
This is the "common" lead.
- Put one lead of the DMM on the outside common flipper lug
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