2a. Before Turning the Game On: Check the Coil Resistance.
A very good idea for any unknown game just purchased is to check all
the coils' resistance. If the game is new to you, and you have not
powered it on, a quick check of coil resistance will tell you a lot
about your new game. This takes about one minute and can save you
hours of repair and diagnosing work.
Any coil that has locked on (usually due to a short solenoid driver board
transistor) will heat up and have a lower
total resistance. This happens because the painted enamel insulation
on the coil's wire burns, causing the windings to short against
each other. This will lower the coil's resistance, causing the coil
to get even hotter. Within a minute or so the coil becomes a dead short,
and usually blows a fuse.
If the solenoid driver board (SDB) transistor is repaired, and the game is powered
on with a dead-shorted coil, this will blow the SDB's same transistor again
when the coil is fired by the game for the first time! There is no sense
making more work for yourself. So take 60 seconds and check all the coils'
resistance BEFORE powering the game on for the first time!
In order to check coil resistance, put your DMM on its lowest resistance
setting. Then put the DMM's red and black leads on each coil's lugs.
A resistance of 2.5 ohms or greater should be seen. Anything less than 2.5
ohms, and the coil and/or driving transistor may be bad.
Now remove the wire from one of the lugs of the coil, and test the coil
again. If the resistance is still the same (low), the coil or diode is bad (and
also perhaps the driving transistor).
If the resistance is higher than 2.5 ohms, the coil is good but
the solenoid driver board transistor is shorted and will need to be replaced.
Lastly, the coil's 1N4004 diode could
be shorted too, giving a false low coil resistance. Cut one diode
leg from a coil lug and retest the coil's ohms.
When replacing a coil with a new one, and make
sure there is a 1N4004 diode installed across the coil's lugs. Remember
when reconnecting the wires to the coi that the power wire (usually two
wires or thicker wires) goes to the coil's lug with the BANDED side of
the diode attached. The thinner wire is the coil's return path to ground
via the SDB.
2b. Before Turning the Game On: Removing the MPU Battery and Fixing
Corrosion.
A battery was used on all 1977 to 1985 Bally electronic game
MPU boards to keep bookkeeping, high
scores, and on some games, game options. This battery was a rechargable
nicad battery, and was soldered directly to the MPU board.
The original battery MUST be removed (cut off) immediately, and discarded!
The game will function fine without the battery in place (but we'll talk
about a replacement too).
The battery section of a Bally MPU board. This battery leaked and
corroded the board (see all the green?). None of the components
too seriously seriously effected, but there is still a fair amount of
work here to fix this board.
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The nicad battery used on the MPU board have a nasty habit of leaking
corrosive materials on to the MPU board, damaging it. This happens
because the battery is over-charged by the MPU board, and due to age.
How many 20+ year old batteries have been seen that haven't leaked?
Corrosion DANGER Warning.
Battery corrosion can lead its way to the J4 MPU board connector and
get under the J4 connector's plastic housing. This is important to
note as the J4 connector carries 43 volts to the MPU board through
this connector. The smallest amount of corrosion (or other crud)
under the J4 connector housing can allow the 43 volts DC
to leak onto the 5 volt buss. This can cause failure of every chip on
the MPU board! Because of this, lift the J4 plastic cover with a screwdriver
and check for any corrosion there. An almost imperceptible amount of
corrosion can allows the 43 volts to leak to the 5 volt buss.
Mild corrosion seen here. Although these components
haven't been ruined (yet!), this corrosion should at
least be neutralized with a vinegar and water wash.
Notice the solder pads have turned gray and are no
longer smooth. The 40 pin socket for the chip at the
top of the picture should also be replaced .
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In most cases the corrosion can be repaired. There can be a lot of work
involved in doing this repair correctly, if the corrosion affected
the electronic components and chip sockets.
Can This Corroded MPU be Fixed?
In my opinion, many Bally MPU boards with battery corrosion
can be fixed (I'm taking this approach from a "hobbiest" point
of view). Often a MPU board is sent out for repair, and is
returned not repaired with a note that says,
"not able to fix, too corroded". Perhaps they were right,
but from my experience they should have stated, "not able to fix
economically, too corroded". Remember these repair guys get paid by the hour.
With new replacement MPU boards available for as low as $150, and
if a repair guy gets paid $50 an hour, and he estimates it will
take more than four hours to fix the board, it's just not worth it.
But that doesn't stop you or me (the hobbiest) from fixing the
board! After all, we work a whole lot cheaper.
The Repair Connection has a very nice web page dedicated to
fixing battery corrosion. They explain the pitfalls, and the common
mistakes made when attempting this repair. Check it out at
http://www.repairconnection.com/acid_damaged_mpu.htm
as this is an excellent document. He often uses bead blasting for
corrosion - see the note about bead blasting below.
New Replacement MPU boards.
New replacement MPU boards are now available from:
Personally I like the $200 Alltek board, as it is
the reasonably priced, has improved Bally diagnostics, and is DIP switch
selectable for any Bally/Stern game. But the other two are also well thought
out and seem very good too. And the Repair Connection has a trade in deal
for their board at $150 that is hard to beat!
Can a Small Amount of Corrosion be Bad?
Yes! Even the smallest particle of corrosion on the MPU board or
under a connector's plastic base or under the DIP switches can cause shorts. The size of these
shorts is often so small that they cannot be seen even with heavy magnification.
The slightest amount of corrosion can short out the switch matrix or the power inputs.
Component layout on the Bally MPU.
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Bead Blasting.
A bead blaster is mearly a sandblaster,
but instead of shooting sand, it shoots small ceramic beads. This is
much gentler than sand. To bead blast a board, all the corroded electronic components
should first be removed that are in the effected area. Then the board
can be bead blasted (after bead blasting, the board should still be
neutralized with vinegar, as discussed below).
Finally, new components are installed to replace
the old ones.
Some people claim bead blasting is not a good way to
remove corrosion, as it "embeds" the corrosion deep into the pores of the
circuit board, making it impossible to remove at a chemical level.
This may be true, but many commercial board repair establishments
use this technique to remove corrosion (probably because corrosion
can be removed quickly, with a very professional "look",
using bead blasting). Most individuals don't
have the means to bead blast, so it's not worth arguing this point here.
But please keep this in mind.
Buy a Bally Reset Section Repair Kit.
Depending on how bad the corrosion is, many parts may need replacement. Instead of
ordering all the parts separately, I suggest just buying a "Bally
Battery Corrosion Repair Kit" BALLY35-BA-KIT from
Ed Krzycki (gpe@cox.net).
This kit includes all the resistors, capacitors, diodes, transistors and chips typically
ruined by battery corrosion. For a mere $10 (plus $3.50 shipping), this kit is well worth it.
See Ed's web page at
members.cox.net/gpe/GPE_Kits.html
for more information.
If for some reason the $10 is too much money, here are the typical parts needed for
- U8 - Static RAM type 5101, 450nS.
- 22 Pin IC socket, machine pin type, for U8 chip replacement.
- C1,C2 - Capacitor, 820pF, Axial Ceramic.
- C5 - Capacitor, 4.7uF, Radial Tantalum.
- C3,C13,C80 - Capacitor, 0.01uF, Axial Ceramic.
Note C80 is sometimes mislabeled as "C30" on some Stern M-100 boards.
- CR5,CR7 - Diode, Switching. 1N4148
- CR8 - Light Emitting Diode, Green. Be sure to install it correctly
(note the position of the flat side of the old and new LED).
- CR44 - Diode, Rectifier. 1N4004 (or better)
- R1,R3,R24,R28 - Resistor, 8.2K, 1/4W, 5%
- R2 - Resistor, 120K, 1/4W, 5%
- R11 - Resistor, 82, 2W, 5%
- R12 - Resistor, 270, 1/4W, 5%
- R16 - Resistor, 2K, 1/4W, 5%
- R17 - Resistor, 150K, 1/4W, 5%
- R29 - Resistor, 470, 1/2W, 5%
- R107 - Resistor, 3.3K, 1/4W, 5%
- R112 - Resistor, 1K, 1/4W, 5%
- R134 - Resistor, 4.7K, 1/4W, 5%
- R140 - Resistor, 20K, 1/4W, 5%
- Q1,Q2 - Transistor, 2N3904
- Q5 - Transistor, 2N4403
- VR1 - Diode type 1N4738A, Zener, 8.2V (alternate for 1N9598)
Removing the old battery and fixing corrosion.
Here's another procedure for removing corrosion:
- Remove the MPU board from the head box.
- Cut the old nicad battery off the MPU board and discard.
- If any components are damaged by the battery (look for green and/or gray!),
cut them off (leaving as much of the leg in the board as possible), and discard.
This includes chip sockets. Chips and transistors
are affected more by corrosion than resistors and capacitors. Be more
concerned with these. If Ed's reset kit was purchased above (highly recommended), remove ALL the
components included in the kit from the MPU board.
- To remove the cut off part's legs from the board, apply some new
solder to the leg's solder pad. Then heat the pad and pull the cut off
leg out of the board with needle nose pliers.
- Check the connector header pins for corrosion. If they are green or gray,
replace the header pins. Remove and discard any header pins
that are corroded.
- Desolder all the removed part's holes.
- Desolder all corroded header pins.
- Tip for desoldering
corroded solder: Often solder becomes so grey/black it can't be
heated and desoldered. First try adding some new solder. If that does not work,
take a Dremel tool with a tiny wire wheel to the
grey/black solder joints.
- Hand sand all green/gray areas with 100 or 150 grit sandpaper.
Sand all the grey oxides off the board, so the
underlying solder can be melted.
Sand until the copper is bright, which will allow solder to stick.
If a trace is sanded through, repair it with some
wire or copper solder wick (for large traces).
Another method to remove extreme corrosion is to use a
Dremel moto-tool with a mini wire brush. It does a neat job of stripping the
corroded areas. It would even strip off the defective solder down to copper,
where new solder can be flowed easily.
- Wash the pcb with a mixture of vinegar and water (50/50) to neutralize the corrosion.
Scrub with a toothbrush.
- Rinse the washed board with clean water.
- Rinse the board with 99% pure alcohol. This will disolve and wash
away the water. Repeat this step. The alcohol will evaporate fairly quick.
- Replace all removed components (except the battery!) Any removed chips
should be replaced with good quality sockets or better yet, machine pin strips.
Note any bare copper being soldered may need solder
flux to get the solder to stick.
Mount the new sockets slightly above the board (note
this is not necessary with machine pin strips, and this is
why they are highly recommended!) Then the new socket
they can be soldered on *both* sides of the circuit board (very
easy to do with machine pin strips). Also mount any new parts
(header pins, capacitors, diodes, resistors, etc.) slightly above the board. This is
absolutely necessary, as the "plated through holes" in the circuit
board are most likely damaged from corrosion (or removing the corrosion).
Soldering the new components on both sides of the board is required.
- Replace any header pins that are corroded with new pins.
- Check the connectors themselves! If the board had corrosion,
the connectors pins may
be corroded too! Replace the connector pins (inside their plastic housing)
if any damage is seen (the pins should be clean and shiny).
The board's header pin plastic base may need to be pried up (on
the component side of the board) to
see if corrosion is underneath it. Connectors J4 and J1 seem to be most affected
by corrosion.
- Check for corrosion around and under the DIP switches. Corrosion here can short
the switch matrix lines.
Removing and Replacing Corroded Components.
Step 1: Pry up the old socket base. If a black "open frame" socket (you can
see the circuit board thru the socket frame), it will come right
off easily, leaving the solder-in socket pins in the board. The
brown or black closed frame sockets (Augat or other brands) will not pry
up (don't even try, as these sockets will ALL need
to be replaced); skip right
to step number three. On the black open frame sockets be careful
not to damage any traces while prying with the
screwdriver tip! Once the socket base is pried up, examine
the socket pins for any grey/green corrosion. If the socket pins are
clean and undamaged, press the socket base back onto the pins.
A brown and a black closed frame socket.
There's no way around it, ALL these sockets will
need to be replaced on any Bally MPU board.
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Step 2: If the socket pins are grey or green, the entire socket
will need to be replaced. With the socket base removed, it is
easy to remove the old socket pins. The best way to
do this is to heat each individual pin,
and pull the pin out of the hole with needle nose pliers.
It may be easier to heat the solder joints from the back
(non-component) side of the board because the corrosion is
usually less there, and the solder will melt better.
After prying up the open framed socket base, heat each pin
individually and pull it out with needle nose pliers.
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Step 3: Desolder the MPU board chip holes. Using a desoldering
iron (Radio Shack $10), desolder the holes. It may be easier
to desolder the solder joints from the back
(non-component) side of the board because the corrosion is
usually less there, and the solder will melt better. Sometimes new
solder will need to be added to a solder joint before it can be de-soldered! Sounds
silly, but it works.
Step 4: Examine the connector header pins for corrosion.
Pry up the header pin's plastic
base on the component side of the board to see underneath it,
and around the pins. If any corrosion is found, remove the
header pins so the corrosion can be removed. Especially important
is the J4 (power!) connector. But any corrosion on the MPU board
connectors can cause adjacent connector pins to short together.
Step 5: Examine the DIP switches for corrosion. Any
corrosion around the DIP switches can cause these switches to short
together, giving all kinds of strange switch matrix problems.
Desoldering the holes.
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Step 6: Sand the area with 100 or 150 grit sandpaper
to remove any corrosion.
After the holes have been desoldered, the area
is sanded clean.
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Step 7: Wash the board in a 50/50 solution of white vinegar
and water (as descibed above).
Step 8: After the board is dry, sand the corroded area again with
150 grit sandpaper.
Step 9: Replace any damaged traces on the board. For large
(thick) traces (like the ground rail surrounding the outside
of the board), use desoldering braid. For small traces, use
wire wrap wire. For medium traces, use stranded 24 guage wire.
Use rosin soldering flux (Radio Shack) to help solder stick to
copper.
Step 10: Install machine pin strip sockets, or some other
high quality socket with an OPEN base (so the traces can be seen under
the socket!). Strip sockets are the best because they
allow complete access to the traces around the socket. HIGHLY SUGGESTED:
solder the machine pin sockets from the top of the board too (cheap
sockets will not allow this). Often the plated
through circuit board holes are damaged, and the only connection between the traces
on the top and bottom of the board is the socket's pins.
Use rosin solder flux (Radio Shack) on bare copper to get the solder to stick better.
Machine pin strip sockets. This is the best replacement
socket as it allows access to the component side traces
which would normally be covered by a conventional socket.
Note they come in strips, breakable to the number of pins
needed. Use solder flux on those bare copper traces to get
solder to stick better. Also it's a good idea to solder the
machine pin strip sockets on BOTH sides of the board.
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Mounting the battery back-up capacitor.
A hole is drilled right next to the negative battery mounting
hole for the memory back-up capacitor. This is done because
the capacitor is much shorter than a battery.
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Easier Soldering Tricks.
Often damaged copper traces are difficult to solder. Even after sanding
the traces to a bright copper color, sometimes solder will not stick
easily to the traces. To help with soldering, here are few tips:
- The longer one waits to solder after sanding the traces shiney, the
harder the soldering. Untreated copper will start to oxidize quickly
in the air, from humidity.
- Use rosin flux paste for easier soldering. This is available in
small tubes from Radio Shack. Just apply the paste to the copper traces,
and solder normally. The flux will allow new solder to stick much easier
to copper board traces.
New Battery
To replace the original battery, add a remote three "AA" battery pack and a 1N4001
or IN5817 (better, as there is less forward voltage loss) diode.
Install the
diode with the banded-end connected to the pcb "+" pin, and the non-banded
end connected to the positive lead of the battery pack. The diode is used
so the recharging circuit doesn't try to charge the AA batteries. The game can
also work with no battery. Not having a battery means that your high
scores and operating audits won't be saved. Personally, I find
this acceptable. But some Bally games also save game options (like sound
styles), so you may need a battery in these games, or the sound options
will always go back to the default setting.
Using an inexpensive four AA battery holder, a 1N4004 or 1N5817 blocking diode,
and three AA batteries as a remote battery holder for the CPU board.
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Here's the new 3 AA battery pack installed in a Bally Eight Ball.
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Memory Back-Up Capacitors.
If one insists on having a battery (can't live without those high scores!),
I would recommend installing a memory back-up capacitor instead. These
capacitors will charge when the game is on, and slowly discharge to keep
the memory alive when the game is off. The advantage to these capacitors
is they never wear out, and they won't leak corrosive materials. The best
of all worlds in my opinion. Their down side is the game must be on
for about one hour every month to maintain their charge (though I have
heard them keeping a charge up to six months). Also,
the game must be on for several hours continuously to initially
charge the capacitor. These capacitors are about the size of half a
single AA battery.
Jameco (800-831-4242) sells 1 Farad memory caps,
part# 142957, $3.95 each, $3.49 for ten or more.
Installing the Memory Back-Up Capacitor.
After removing the battery and addressing any board corrosion,
install the memory back-up capacitor.
Drill a hole for the second lead of the back-up
cap, just to the side of the negative battery
lead (see picture above). Then mount the cap in the board, and bend
the leads to hold it in place. Solder the cap in place.
On the second lead which goes throught the hole drilled,
solder a two inch wire. Extend the wire
to the other battery terminial hole on the MPU board.
Note the minus and positive leads were not labeled
on the cap I installed. There was only a black line on the cap to
designate the negative lead.
If the memory cap does not stay charged and keep scores for
say a month, there are a couple
things to check. First is make sure power is not getting
past 1n4148 blocking diode CR5 (that is, the memory cap is only powering
the 5101 RAM and not the entire board.) With the game off there
should only be DC voltage on one side of this diode, not both sides. Also check
the resistance of R12 (270 ohms). If this resistor goes open or is too high
of a value, the memory cap will never charge. And finally the brand
and type of 5101 will affect how long the game 'remembers' (for
example the PCD5101P RAM works well with a memory cap).
The underside of the MPU board with the memory back-up cap installed.
Note the positive cap lead that goes through the newly drilled hole
must be jumped back to battery board solder position.
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The memory back-up capacitor, installed in the MPU
board. Note the cap lead with the black lines going
to it is the negative lead.
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Check U8 RAM for Battery Voltage.
With the new battery pack or capacitor (charged) installed and
the game OFF, check
the U8 5101 RAM at pin 22 for 4 to 4.6 volts (use ground for the
black lead of the DMM, and U8 pin 22 for the red lead). If
there is no voltage, there is a problem with the backup cap
or remote battery holder, or with the traces going from
the original battery solder pad to the 5101 RAM (very common since it's
in the 'corrosion zone'.)
2c. Before Turning the Game On: Rebuilding the Power Supply
- Blown Fuses and What Causes Them
The Stern and pre-1981 (before Xenon) Bally power supply's rectifier board (-18 and -49) on
Bally electronic games is notorious for being under-powered and
troublesome. I suggest doing these power supply modifications before even turning
the game on. Chances are there is a rectifier board problem anyway!
There are three different version of the Bally electronic rectifier board.
The most common is AS2518-18 (which is identical to the rectifier board
used in Stern games too). This is the most troublesome design,
and will require some upgrades. The least common is AS2518-49,
and was only used on Kiss, Future Spa, and Space Invaders.
This rectifier board also will need some upgrades.
The AS2518-54 rectifier board as used in Xenon (10/80) and
later is quite good, and requires no upgrades (other than possibly
replacing header pins, if tarnished).
First Check the Test Points.
On -18 and -49 power supplies (pre-Xenon),
before beginning make sure your transformer and regulator board work.
Attach only connector J2 (remove connector J1 and J3). J2 brings 120 volts from the power cord
to the transformer and regulator board, which allows us to check the test
points for proper voltages.
The best place to pick up ground is at resistor R1 or R2's ,
lead closest to the fuses (or on rectifier board AS2518-54,
on the right side of the R1 resistor). This info applies to all three generations
of rectifier boards (AS2518-18, AS2518-49, AS2518-54).
- TP1 (on AS2518-18) = 5.4 volts DC +/- .8 volts (4.6 to 6.2 volts).
Fuse F1, bridge BR1. Used to power the "switched illumination" (feature lamps).
- TP1 (on AS2518-49 & -54) = 6.5 volts DC (5.8 to 7.2 volts). Fuse F1, voltage
regulator RP1 and RP2. Used to power the "switched illumination" (feature lamps).
- TP2 = 230 volts DC, +/- 27 volts (203 to 257 volts). Fuse F2, diodes CR1 to CR4.
Used to power the score displays.
- TP3 = 12 volts DC (11 to 16 volts). Fuse F3, bridge BR2.
Used to power the regulated +5 volts DC for the game's logic circuits.
- TP4 = 7.3 volts AC, +/- 1.0 volts (6.3 to 8.3 volts). Fuse F5.
Used to power the general illumination.
- TP5 = 43 volts DC, +/- 5.4 volts (47.6 to 48.4 volts). Fuse F4, bridge BR3.
Used to power all the coils.
If fuse F2 is blown and no high voltage at TP2,
almost for certain one of the four 1N4004 diodes next to fuse F1
are shorted. Use a DMM set to the diode function and test the diodes. In one direction
.4 to .6 volts should be seen, reverse the leads and null voltage should be seen.
If fuse F3 is blow, suspect bridge BR2 as shorted. If fuse F5 (TP4) is blown there is
a short in the general illumination circuit. If fuse F4 is blown, suspect bridge BR3
as shorted.
-18 Fuse F1 and Test Point TP1 - CPU Controlled Lamp Power.
If there is no DC voltage at TP1 (voltage for the CPU controlled lamps, first check
the fuse holder for fuse F1. Often this fuse holder is badly tarnished and
needs to be replaced with new Tin plated Beryllium Copper fuse clips
(marked "BC" for Beryllium Copper). Do NOT use
Tin plated Brass fuse clips for F1, as they can not handle the current required.
If fuse F1 is blown, suspect bridge BR1 as shorted. Again this is very common.
The -49 rectifier board with the two VAROs (heat sinked transistor-looking
devices at the top of the picture).
Picture by Steve.
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-49 Fuse F1 and Test Point TP1 - CPU Controlled Lamp Power Problems.
The -49 power supply used on Kiss, Future Spa and Space Invaders had a more
robust CPU controlled lamp circuit on the rectifier power supply board.
This happened because these three games had more CPU controlled lamps
than other pre-1981 games (thanks to an Auxiliary lamp driver board used in
these three games). Instead of using a VJ248 8 amp bridge rectifier to convert the AC transformer
voltage to DC, these games used two "Positive Center Tapped Silicon Rectifiers
30A (15A per Diode)", or "VARO Dual Diode Rectifiers". Unfortunately these
are no longer available (though sometimes they can be found from NTE under
part numbers NTE6200, NTE6202, NTE6206, NTE6208 or NTE6210).
If the -49 power supply shows no voltage at TP1 and the fuse F1 is good (or keeps blowing),
chances are good either one or both VARO dual rectifiers are bad.
First check for the AC voltage by putting a DMM leads on the
metal case of each of the two VARO rectifiers (aka E9 and E10). About 9 to 10 volts AC
should be seen. If test point TP1 shows low or no DC voltage, one
or both of the VAROs is bad.
Since the dual diode VARO is no longer available, the pair can be
replaced with a single modern 35 amp 200 volt wire lead bridge rectifier.
This will actually give a slightly more robust rectification (35 amps
versus the original 30 amps), and the modern style wire lead bridge
is readily available for under $5.
Replacing the -49 VAROs with a Single Bridge Rectifier.
Here are the step to replace the pair of -49 VAROs with a single 35 amp bridge
rectifier:
- Remove the two screws securing the two small 8 amp bridge rectifiers to their
metal base plate.
- Flip the rectifier board over and remove the four nuts holding the VARO
rectifier in place.
- Remove as much solder as possible from the two VARO leads and discard
the two original VARO rectifier.
The fuse side of the -49 rectifier board with the two VAROs removed.
Picture by Steve.
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- On the fuse side of the rectifier board, label the VARO pads with
a Sharpie to avoid confusion.
Labeling the fuse side of the -49 rectifier board with the two VAROs removed.
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- Put about 1/2" of 1/8" heat shrink tubing over the *UPPER* AC wire of the
bride rectifier. Lay a new wire lead 35 amp 200 volt (or higher) bridge rectifer on
the fuse side of the rectifier as shown in the picture below (see picture below). IMPORTANT:
notice the orientation of the offset "+" lead of the bridge.
On the back (solder) side of the rectifier board, attach a piece of wire from
the heat-shrunk AC bridge lead over to the far AC board solder point. Solder the
other AC lead and the Pos and Neg leads of the bridge (see picture below).
Mounting the new wire lead 35 amp bridge rectifier on the -49 rectifier board.
BEFORE soldering it in place, put some heat shrink tubing over the UPPER *AC*
lead of the bridge rectifier. Also note the orientation of the "offset"
(the + lead) of the bridge rectifier.
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Solder side of the -49 rectifier board showing the heat shrunk AC bridge lead.
Notice how its jumpered to the far rectifier board AC solder point.
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- Bolt a heat sink on the top side of the new bridge. This is required and
it is important, do not skip this step.
- Bend the bridge's wire leads so they fit into the mounting holes as required.
- Solder the new bridge into place on the fuse side of the rectifier board.
The new wire lead 35 amp bridge rectifier solder in place on the -49 rectifier board.
Note the orientation of the "-" and "AC" bridge rectifier leads and the heat shrunk
tubing bridge lead.
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The SINGLE new wire lead 35 amp bridge rectifier solder in place on the -49 rectifier
board, replacing the TWO original Varo units. The original 12 volt rectifier was also
replaced on this board (the large lower bridge).
Note a 120 volt power cord is connected to J2 pins 6,7 so the board can be
"bench tested" for the proper voltages, before installing it back in the game.
Also a circuit breaker is temporarily used for the F1 fuse. This makes testing the new
replacement bridge for the lamp matrix easier (if there's a short, you won't blow
through a bunch of costly fuses).
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The Power Cord.
Make sure it's a three prong cord. If someone cut off the third prong,
replace the cord and/or the plug. The third GREEN wire goes to the line interface filter.
That's the small silver box in the bottom of the cabinet (see below).
The Varistor.
Known as VR1, the varistor's job is to aborb large voltage spikes.
The first thing the power cord attaches to is the varistor.
If the power line gets struck by lightning, the voltage
spike coming down the power line can toast anything in its path.
The varistor will absorb this spike and short itself, preventing
damage to the game (electricity will take the shortest
path of least resistance). A blown varistor is usually obvious; it will no longer
look like a red disc capacitor, but will be a molten mess with two
wires attached to it.
The red varistor and the line filter, as found
in the cabinet of a Bally game.
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The Line Filter.
The line filter is the next thing connected to the power cord. It's a
small silver box that prevents the game from making line noise (which
could be "heard" by other products like stereos). Not much to go wrong
here, but occassionally these go bad and short.
On/Off Switch.
Next in line is the on/off switch. These too can go bad, but it doesn't
happen often. Just before the on/off switch is a service outlet. It's
always on, whether the game is switched off or on.
Left: AS2518-18 Power supply as used in most Bally games until 1981.
Stern also used a design identical to this one.
Right: AS2518-49 Power supply as used in Kiss, Future Spa, and Space
Invaders. Notice the two big heat sinked, metal cased voltage regulators.
These don't exist on the AS2518-18 power supply. The AS2518-49 power
supply board is exactly like the AS2518-18 board, except for the removal
of BR1, which is replaced by these two heat sinked voltage regulators.
Also the -49 added one pin to connector J1 (to double up the switch
illumination feature lamp line).
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The Rectifier Board.
The rectifier board takes AC voltage from the transformer and
converts it to unfiltered DC voltage.
Bally used three different rectifier board in thier games from 1977 to 1985.
The part number is silk screened right on the printed circuit board.
- AS2518-18 (used from 1977 until 1981, except in Kiss, Future Spa and
Space Invaders).
- AS2518-49 (used only in Kiss, Future Spa and Space Invaders).
- AS2518-54 (used in Xenon and later).
Prior to Xenon (late 1980),
the actual power supply is in the backbox (head) of the game. It's
usually located in the lower right corner (as facing the game).
It comprises a large transformer, a silver platform, and a smallish
printed circuit board known as the rectifier board. Most of the
game fuses are located on the
rectifier board (there is usually at least one playfield
fuse too).
AS2518-54 Power Supply module, located in the lower
cabinet, as used starting in 1981.
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Differences between -54 and -132 Power Modules.
The -54 power module was used starting with Xenon.
The -132 power module was used on Baby Pacman and Granny and the Gators.
These two power modules are largely the same with some minor changes.
Like -54 uses 3 amp diodes for CR5-CR8, where -132 uses 6 amp diodes. Better heat
dissipation with the 6 amp diodes, and can retrofit a -54 with 6 amp diodes at CR5-CR8.
The -54 has single fuse (F5) for the GI circuit, where the -132 breaks the circuit into two
strings with two fuses (F5,F6). Should still be able to use a -132 in a
-54 machine. I don't suggest using a -54 in a -132 game though, as the GI circuits
are heavily used in those two games - the GI circuit is used for the zero
cross for the CPU controlled lamps, so blowing a GI fuse will also take out
the CPU controlled lamps on Baby Pac/Granny.
How the Power Supply Works.
Power comes into the rectifier board from the line cord at
connector J2, pins 6 and 7. It then goes to fuse F6 (3 amp slo-blo),
and then to the transformer (primary). The transformer splits the
voltage into five different AC voltages. Then these voltages
run through their own fuse. Some of the voltages (7.8, 12, 49 volts AC)
go to a 200 volt, 8 amp bridge rectifier which converts the
AC voltages to DC (+5.4, +11.9, +43 volts DC respectively).
The 7.3 volts AC stays AC, and powers
the game's general illumination. The 173 volts AC that is used for the
displays is converted to 230 volts DC by four 1N4004 diodes (CR1 to CR4).
If there is a AS2518-49 rectifier board, this works identical to the above described
AS2518-18 model. The only difference being there's no 7.8 vac and no bridge BR1. Instead,
9.2 vac comes from the transfomer, and is converted to 6.5 vdc by
two heat-sinked 200 volt 30 amp voltage regulators. It works exactly the same
as the previous model, and has the same pin out (except for one extra
pin on J1), but has a beefier +5 volt output.
AS2518-18/-49 Power Supply connector pinouts (located in the backbox 1977-1980).
Note -49 has an extra ninth pin at J1. picture by t.callahan.
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Header Pins and Connector Pins on the Rectifier Board.
Due to the age of these games, I can almost guarantee that the
.156" connector header pins on the rectifier board are at least slightly
brown (regardless of the generation of power supply used).
If this is the case, these pins are acting like more like resistors
than connector pins. These should be replaced with new header pins. And
likewise, the female terminal pins in the connector housings should also be replaced
with new Molex Trifurcon pins (only use Trifurcon pins, as they have more
pin surface area, and last longer).
Make sure both are replaced! Replacing only the header pins or
the housing pins will make the new part brown in a short time
(wasting time and money). See the
Connector web page for more details
on these connector pins.
Trifurcon Connector Pins.
Molex makes a crimp-on .156" size female terminal pin called a
"trifurcon" pin (not available in the .100" pin size).
This style .156" pin differs than the
"normal" pin; the metal material is more heat resistant,
and it has three wiper contacts instead of just one.
The more contact points means the female pin "hugs" the
male header pin with greater surface area. I highly recommend these.
See the connector section and the
connector web page
for more details.
Check Rectifier Connector J3 Pins 8,17.
On the power supply's rectifier board, connector J3 can often
be over stressed and burned. In particular, connector J3 pin 8 (orange wire, +5 volts)
and J3 pin 17 (white wire with a
brown trace, ground) are often burned (both of these pins go to the Voltage Regulator/Solenoid
Driver board).
If either of these pins are even slightly brown, both the header pins and
the connector pins should be replaced. Trifurcon replacement pins are
highly recommended.
Bridge Rectifiers, Diodes, Voltage Rectifiers.
The bridge rectifiers are one of the Bally power supply's weak links.
The stock VJ248 bridges (200 volt 8 amps) are just too small to do the job. These
will need to be replaced with 25 or 35 amp bridges. The
bally rectifier board also uses four 1N4004 diodes CR1 to CR4 for the 173 volts AC
used to power the score displays. These do essentially
the same thing as a bridge. There isn't much current draw on these diodes, so
they usually don't fail. But when replacing these, use 1N4007 or better diodes.
On the AS2818-49 rectifier board, bridge BR1 is replaced
with two voltage regulators. These are R712, which are
200 volt, 30 amp devices. This rectifier board design is heavier duty then
the AS2818-18 model.
- BR1 (AS2518-18 only): converts 7.8 vac to +5.5 vdc (through F1). Used
for the "switched illumination" (feature lamps).
- RP1, RP2 (AS2518-49 only): replaced BR1 (as used on AS2518-18) with
two voltage regulators, which converts
9.2 vac to +6.5 vdc (through F1). Used
for the "switched illumination" (feature lamps).
- BR2: converts 12 vac to +11 to 16 volts DC (through F3). Used to created the regulated
+5 volts DC to power the logic chips.
- BR3: converts 49 vac to +43 vdc (through F4, uses a varistor too). Used
to power all the game's solenoids, including the knocker (in the backbox
or lower cabinet) and also goes to the sound board on many games.
- CR1 to CR4: converts 173 vac to +230 vdc (through F2) using four 1N4004 diodes.
Used to power the game's score displays.
The rectifier board as used in AS2518-18.
The bridges are mounted underneath this board.
The three phillips head screws need to be removed
to access them. The big red disc capacitor-looking
device is a varistor. Note the test points across
the top edge.
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Left: The bottom side of the AS2518-18 rectifier board. Note the three
small square bridge rectifiers. These will be replaced with larger 25 or 35
amp rectifiers. The one large bridge shown above the installed three is a
replacement 35 amp bridge.
Right: The bottom side of the AS2518-49 power supply. Note the two
small square bridge rectifiers, which will be replaced with larger 25 or
35 amp rectifiers.
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On the AS2518-18 and AS2518-49 rectifier boards, the bridges
are mounted on the back of the board,
and are bolted to a large metal heat sink. This allows the bridges
to run cooler. The phillips head screws on the power
supply board hold the bridges to the heat sink.
Remove these three screws to remove the board.
Note that the 49 vac that is converted to 43 vdc also has a
varistor mounted in it's circuit too. The varistor will short
if more than about 55 volts goes through it, when will instantly
blow a fuse. This is an over-voltage protection.
Power Supply "Test Points" (TP).
Bally rectifier boards have five "test points" where the
proper output voltages can be checked. To do this, the game need to be powered on and in
"attract" mode. The best place to pick up ground is at resistor R1 or R2's ,
lead closest to the fuses (or on rectifier board AS2518-54,
on the right side of the R1 resistor). This info applies to all three generations
of rectifier boards (AS2518-18, AS2518-49, AS2518-54).
- TP1 (on AS2518-18) = 5.4 volts DC +/- .8 volts (4.6 to 6.2 volts).
Fuse F1, bridge BR1. Used to power the "switched illumination" (feature lamps).
- TP1 (on AS2518-49 & -54) = 6.5 volts DC (5.8 to 7.2 volts). Fuse F1, voltage
regulator RP1 and RP2. Used to power the "switched illumination" (feature lamps).
- TP2 = 230 volts DC, +/- 27 volts (203 to 257 volts). Fuse F2, diodes CR1 to CR4.
Used to power the score displays.
- TP3 = 12 volts DC (11 to 16 volts). Fuse F3, bridge BR2.
Used to create the regulated +5 volts DC for the game's logic circuits.
- TP4 = 7.3 volts AC, +/- 1.0 volts (6.3 to 8.3 volts). Fuse F5.
Used to power the general illumination.
- TP5 = 43 volts DC, +/- 5.4 volts (47.6 to 48.4 volts). Fuse F4, bridge BR3.
Used to power all the coils.
If getting a voltage below the above value ranges, that associated bridge
rectifier is probably bad and needs to be replaced. If TP4 is out of limits,
the transformer may need to be replaced! TP4 is an AC voltage that
doesn't get converted to DC, and hence doesn't have a bridge rectifier.
Check the Rectifier Board Fuse Clips (HOT fuses!).
Often the metal clips that hold the fuses in place on the
rectifier board fatigue, corrode, and turn brown in color. This can cause a bad
connection with the fuse. These fuse clips need to be
replaced! They have become hot and are acting like resistors,
not connectors. Also these clips can fatigue and not have
a good "spring" action to them. This means the clips
again don't make good contact with the fuse. There is
no fix for this; just replace them!
The high amp fuses on the rectifier board show this problem the most.
These fuses will get hot the quickest, and can generate a lot of heat.
Once the fuse clips get hot and discolor, they
must be replaced to fix this problem. Tin plated brass fuse clips
work fine for low current and low voltage fuses. But for high current
and/or high voltage circuits, use tin plated beryllium copper fuse clips
(actually it's a good idea to just use tin plated beryllium copper
fuse clips for all the fuses).
First Upgrade: #47 Light Bulbs instead of #44.
This "upgrade" is actually VERY important! Change ALL the
playfield light bulbs from #44 to #47 bulbs. The #47 bulbs consume
less power, and put less of a strain on the power supply's
transformer, connectors, and bridge rectifier. Sounds ridiculous,
but it's true. The difference in amperage is very small, but with
75 of these lamps, it really adds up!
Number 47 lamps are a 150 mA (0.945 watt) lamp, where #44's are 250 mA
(1.575 watts) lamp. The difference between the two lamps is 100 mA (.63 watts).
If there are 75 of these bulbs, having #44's installed is like adding a
50 watt light bulb to the game. The additional power consumption uses more produces more
heat and strain on the connectors and plastic game parts.
Replacement Rectifier Boards.
The Repair Connection (www.repairconnection.com)
has a replacement
rectifier board available (including for Kiss, Space Invaders and Future Spa)
for games before Xenon. If fixing/updating a 1977-1980 rectifier
board is not possible, this is an excellent replacement. More info on this
replacement can be found at
www.repairconnection.com/dualplug.htm.
Rectifier Board Upgrades for AS2518-18 / AS2518-49 and Stern.
If the game has a Stern or Bally AS2518-18 or AS2518-49 rectifier board (pre-1981),
these upgrades need to be done. Note the Stern rectifier board is identical to
Bally's AS2518-18 model. This will make the power supply more
reliable. Note that after making all these upgrades, one could
use an older AS2518-18 power supply in a game calling for
the AS2518-49 power supply (they are pin compatible, except for
an added pin to double up the switched lamps on connector J1).
However the whole power supply must be switched (including the transformer),
and not just the rectifier board. Not advisable to switch, but it can
be done in a pinch if these modifications are made. Note female connector
J1 will have on extra pin that will hang over the edge of the
J1 male pins.
- Replace ALL the .156" header pins on the rectifier board.
Chances are these header pins are brown. Even if just slightly
burnt (brown), this means the pins are acting like small resistors.
Replace them all with new pins. Sanding the pins and re-tinning them
is only a short term fix. Sanding removes the protective plating
on these pins, which means they will brown up quickly again.
Just replace all the pins and be done with it.
When replacing the header pins they are also being re-soldered, which
solves another common problem of cracked solder joints on these pins.
Also on the larger .156" connector pins (all the pins in the power
supply are this size), replace the plastic connector's terminal pins with Molex
.156" Trifurcon pins. See the
connnector web page
for more details on connector pins.
Mod 2: adding a jumper from J1 pin 5 to J3 pin 10 on the solder side. Note
the convenient plated through holes were used for the wire.
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- On the solder side of the rectifier board,
add a jumper wire from J1 pin 5, to J3 pin 10. Note there are plated through holes
in the circuit board that make this mod very easy. This
adds additional area for the 7.3 vac general illumination lines.
Mod 3: adding a jumper from J1 pin 6, to J3 pin 9 on the solder side.
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- On the solder side, add a jumper from J1 pin 6, to J3 pin 9. Since there are no
plated through holes here, solder the wire directly to the
header pin and the circuit board trace. This
adds additional area for the 43 vdc solenoid lines.
- On the component side, drill a 5/64" hole to the left of the
header jack J1. Drill this hole exactly where shown in the
picture below, which is to the left of the marking "J1".
If a AS2518-18 is being modified, also drill another 5/64" hole
to the left of the header jack J3. Drill this hole exactly where shown in the
picture below, which is to the left and above the marking "J3".
NOTE: Drilling these two holes is optional.
Mod 4 & 5: On the component side a 5/64" hole was drilled next to
the marking "J1". On rectifier board AS2518-18 (only), another
hole above and next to the "J3" marking on the board was drilled.
The drilled holes are optional (the wires can also just wrap around
the edge of the board).
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- On the component side
scrape the green solder mask off the surrounding ground trace which
the hole(s) goes through. If no hole(s) were drilled, still scrape
the green solder mask off the large ground trace, to the side of the header pins
(where the hole(s) would have been drilled). Solder wire(s)
to this trace and fed it through the drilled hole(s).
If no holes were drilled, the wire can instead be
fed around the edge of the board. On the solder side, solder the other
end of the wire to head pins J1-1/J1-2. This
adds additional area for the 7.3 vac general illumination ground lines.
For AS2518-18 only, solder the second wire
to pins J3 pins 1,2,3,4 on the solder side of the board. This wire
add additional ground area for the lamp driver ground.
Mod 4 & 5: On the solder side, the wires go through the drilled holes (or
around the edge of the board, if the optional hole(s) are not drilled) and
soldered to their respective header pins. The J3 modification is only needed
on rectifier board AS2518-18.
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- Desolder the three (or two, if it is a AS2518-49 rectifier board)
bridges from the bottom of the rectifier board.
Mounting the larger 35 amp bridge on the component side of
the AS2518-18 rectifier board. The middle bridge must be mounted
first! Note the "notch" in the bridge (the "+" lead) is mounted
at the top. Add heat sinks to the bridges BEFORE installing them
as it's a lot easier (not shown).
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- If it is a AS2518-18 rectifier board (with the three bridges),
install a new 25 amp, 200 volt (or higher) wire lead bridge in the
middle position, on top of the rectifier board (originally
the bridges were soldered to the bottom of the board).
Note the offset lead (and the notch) on the bridge is the "+" lead of the bridge.
Install the bridge at least 1/2" off the board to allow good air
flow under the bridge. Do not solder the bridge in place yet.
Add heat sinks to the bridges before installing them. These were available
at Radio Shack (part# 276-1363 or 276-1368) but they now seem discontinued.
So it's better to get these wire lead bridges from
Great Plains Electronics (GBPC3502W) or
Competitive Products.
AS2518-18: Notice the "dog leg" bends in the power supply leads to
allow these larger bridges to be used. Again note the "+" lead is
mounted at the top.
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AS2518-49 (as used on Kiss): The "dog leg" bends are less
prevalent here because there are only two bridges to install
on this rectifier board.
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- Install the remaining bridge(s) (either model rectifier board).
To install them, "dog leg" the bridges to
get them to fit. It's Ok if the bridge's metal casing touch.
Install the bridges at least 1/2" off the board to allow good air
flow underneath. Do not solder the bridges in place yet.
Left: A top view of the newly installed bridges on a
AS2518-18 rectifier board.
Right: A top view of the newly installed bridges on a
AS2518-49 rectifier board.
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- Before soldering the bridges in place, it's a good idea
to bolt a heat sink to the top of the bridge. This is optional,
but highly recommended (see below for more details).
At minimum BR1 absolutely needs a heat sink.
- After all the bridges are installed, and their placement is good,
solder them in. Solder the bridge leads on both the front
and back sides of the rectifier board, to ensure good contact.
- Replace diodes CR1, CR2, CR3, CR4 with new 1N4007 diodes. Make sure
to install the new diodes with the band in the same direction!
These diodes are used for the high voltage (score displays), and are
often heat damaged.
- Check that resistor R2 (25 ohms 5 watts) is not damaged. Check
its value with a multi-meter. This resistor gets quite warm
during operation, and can crack. Replace if a value is seen outside
23 to 27 ohms.
- Check that the correct fuse values are installed in the rectifier board.
- When installing the rectifier board back onto its plastic
standoffs, note the screws and the metal heat sink
plate used to bolt the bridge rectifiers to the metal case are no longer needed.
These may be discarded.
Install heat sinks BEFORE soldering the bridges
in place! (it's a lot easier to do it before). I bought
my bridges, heat sinks, and heat sink compound at
Radio Shack. The heat sinks are really designed for
transistors, but they work well on the bridges too.
At minimum make sure BR1 has a heat sink.
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Installing Heat Sinks on the Bridges.
Bridges can fail from heat fatique.
Installing a heat sink increases the surface area of the
bridge, allowing it to cool easier. It really is a good
idea as any bridge installed will get hot. At minimum BR1
definately needs a heat sink.
Aluminum transistor heat sinks are available
at Radio Shack part #276-1363 or #276-1368. They
bolt right to the top of the bridges. The 276-1368 model uses a
4-40 screw (not included). Make sure to buy some heat sink
compound (Radio Shack part# 276-1372) too. This aids in the heat
transfer from the bridge to the heat sink. It is required!
Just spread a thin layer on the top of the bridge before bolting
down the heat sink. Get one heat sink per bridge.
Note it's a lot easier to install
the heat sink BEFORE soldering the bridge in place.
Testing rectifier board upgrade work on
the bench. Just hook up 110 volts to connector
J2 pins 6 and 7, and the voltages can be tested
at the test points. Here we're testing TP2.
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Testing Rectifier Board Upgrade Work.
After doing all the previous rectifier board modifications,
test your work right on the bench, without
installing the power supply back into the game.
To do this requires only a power cord, and two
alligator clip wires.
Connect the two alligator clip wires to connector J2, pins 6 and 7 on
the rectifier board. Then connect the other end of each
aligator clip to a 110 volt power cord. When plugging the line
cord into the wall, the power supply will be turned on.
Then test the rectifier board's "test points" for proper voltages. The voltages
may be slightly different than previously dicussed above, since
there is no load on the power supply. No load can cause voltages to vary somewhat.
Connect the black (negative) lead of a DMM multi-meter to
R1 or R2's lead closest to the fuses. This is approximately the readings that should be seen:
- Gnd (AS2518-18/-49): R1 or R2's lead closest to the fuses.
- Gnd (AS2518-54): R1 lead on the right.
- TP1 (AS2518-18): 6.4 volts DC.
- TP1 (AS2518-49): 8.2 volts DC.
- TP2 = 195 volts DC (could be as low as 150 volts).
- TP3 = 13.5 volts DC.
- TP4 = 7.5 volts AC.
- TP5 = 47 volts DC.
If the voltages seen are drastically different than the above,
check your work. Also check resistors R1 (600 ohms) and R2 (25 ohms).
Test your work with the power supply installed in
the game. Just hook up connector J2 (only!), and leave J1 (playfield
power) and J3 (logic board power) disconnected. Turn the game on
and check the voltages as described above. Having the J1 and J3
connectors removed will isolate the power supply from the
rest of the game.
Power Supply AS2518-54 Rectifier Board Upgrades.
The power supply changed for all games Xenon and
later. Instead of a bridge to rectify 12 volts AC to
+5 volts DC (though bridges are still used for the switched lamps
and the solenoid voltages), four individual diodes were used. These diodes
can become "leaky" (they normally run somewhat hot).
This can cause AC ripple to enter the
+5 volts logic circuits, which can cause the game
to reset or have other intermittent problems.
For games this age, these diodes should be replaced!
The replacement diodes should be a 6A50 (6 amp, 50 volt or higher)
diodes (games Eight Ball Deluxe and later were fitted with
this size diodes). Higher voltage diodes can be used too,
like a 6A2 or 6A200 (6 amp, 200 volt) or even 6A4 (6 amp 400 volts).
Radio Shack sells a decent replacement, part number 276-1661.
Also, 1N4004 or 1N4007 diodes could be used, but this is not
recommended! The amp rating on 1N4004/1N4007 diodes is only 1 amp,
compared to the 6 amp diodes that should be used.
Blown Fuses and What Causes Them.
Rectifier Board Fuses.
Here is a list of the rectifier board fuses. This applies to all generations
of Bally power supplies from 1977 to 1985.
- F1 = 10 amp fast-blo (CPU controlled feature lamps, pre-Xenon). 20 amp fast-blo for
Xenon and later games.
- F2 = 3/4 amp slo-blo (score display high voltage)
- F3 = 4 amp fast-blo (unregulated +5 volts)
- F4 = 5 amp fast-blo (solenoids, if game has 2 flippers)
- F4 = 6 amp fast-blo (solenoids, if game has 3 flippers)
- F4 = 7 amp fast-blo (solenoids, if game has 4 flippers)
- F5 = 20 amp fast-blo (general illumination lights)
- F6 = 3 amp slo-blo (incoming 120 volts AC line power)
Bridge Rectifiers and Fuses That Always Blows.
If powering on a game, and the fuse immediately blows,
there's a good chance one of the bridge rectifiers is shorted.
Try replacing the fuse's associated bridge. Or just do the
modification listed above (which replaces the bridges with bigger models).
- F1 - BR1 (or on AS2818-49, one or both of the voltage regulators RP1, RP2).
Used to power the "switched illumination" (feature lamps).
- F2- CR1 to CR4 (four 1N4004 diodes that act like a bridge). Used
to power the score displays 190 volts. Often one of these 1N4004 diodes
will short internally and cause fuse F2 to blown immediately when game
is powered on.
- F3 - BR2. Used to power the regulated +5 volts DC.
- F4 - BR3 (check varistor on the rectifier board too, its the large red disk).
Used to power the coils 43 volts. Also goes to the MPU board, Solenoid driver board, and the
sound board. Very common to see a short somewhere in the 43 volt power
train causing this fuse to blown at power-on.
- F5 - no bridge. Short in the 7.3 volt AC general illumination circut.
- F6 - no bridge. Short in the main 110 volt AC power circuit.
Check the varistor and the line filter in the cabinet.
Fuse F4 - The Playfield Solenoids Don't Work.
First thing to check is the under the playfield fuse might be blown.
Next check fuse F4 on the power supply regulator board. Also check
it's fuse clip is in good condition with good tension, and is not brown. Now check TP5
(test point 5) on the power supply regulator board. A voltage of about 43 vdc should be seen. If
no voltage at TP5, assume the bridge BR3 on this board is bad and
replace it.
After getting +43 vdc at TP5, then check power supply
connector J1 pin 6. This brown wire goes directly to the playfield flipper
coils. If there is +43 volts at the connector, but not at the brown
wire on the flipper coils, there is a problem in the wiring. Here's a breakdown
of where the 43 volts goes on most games:
- Power supply J1 pin 6 goes to the flipper coils on the playfield.
- Power supply J3 pin 9 goes to the Solenoid driver board's flipper coil relay.
- Power supply J3 pin 12 goes to MPU board connector J4 pin 15.
- Power supply J3 pin 13 goes to the knocker in the backbox. Note some games have the
knocker in the cabinet, hence this pin is not be used on all games.
- Power supply J3 pin 19 comes from the Solenoid driver board J3 pin 23 and
is the 43 vdc solenoid return (ground).
- Power supply J3 pin 20 comes from the Solenoid driver board J3 pin 24 and
is the 43 vdc solenoid return (ground).
- Solenoid driver board J1 pin 6 goes to the playfield flipper coils.
- Solenoid driver board J3 pin 5 goes to the sound board J1 pin 9 on many games.
Also note +43 volts on some games is used on the early A8 sound
board (Lost World to Dolly Parton). A problem on this sound board (or
a bad connector there) can cause problems. Though some sounds boards do not
use the 43 volts, the wiring may still be present that brings 43 volts
to the sound board. Remove the sound board connectors for testing purposes.
If the game is not getting the 7th MPU LED flash, that means +43 volts
is missing. After checking all the above, verify there is +43 vdc on
the MPU board on the left (connector) side of R113. Now check the right
side of R113. If no voltage there, then replace R113 (2k, 1/4 watt) and
retest. If still no voltage, there may be battery corrosion damage in
this area of the MPU board.
Fuse F5 - General Illumination (G.I.) Fuse Woes.
There isn't much to this circuit,
so if fuse F5 blows, this usually means there is a shorted general
illumination bulb or socket. This is never a quick or easy fix -
you'll have to do quite a bit of looking and eliminating to find the
problem.
First, a good idea is to purchase a clip-on circuit breaker. Instead
of replacing the F5 fuse for each test "power on", the circuit breaker
can be reset and reused. This is great |
