3a. When things don't work: Making a MPU Test Fixture.
If your game is not working, chances are the MPU board is at fault. To fix
the board, you'll have work on it on your bench, then install it in the
game to test it. I found this too tedious when doing MPU repairs. Instead,
I constructed a simple test fixture I would use to test the MPU board right
on my workbench.
The J4 MPU Board Connector.
If you don't want to make a work bench test fixture for repairing
your Bally MPU board, there is an easy way around this. Assuming
your Bally power supply is working correctly in your game, when testing a Bally
MPU board, you only need to use connector J4 on the MPU board.
The J4 connector is the power connector. With it only attached and
a working power supply, you can quickly test your Bally MPU right in the game.
Making a Test Fixture.
To make a test fixture, you will need some sort of power supply that will
deliver +5 and +12 volts. You can buy a video game switching power supply
(about $25), or you can use an old computer power supply. Either will work
fine. Old computer AT or ATX power supplies are plentiful, and often $15 or less
used at computer stores.
On the left is a video game switching power supply.
On the right is a used computer AT power supply. Either
will work fine for a test fixture. Note the computer
power supply connector on top of the box is the one
that will supply our +5, GND and +12 volts. This plug
was used to power drives (hard drive, CD rom, etc).
Red is +5, black is GND, and yellow is +12.
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When it comes to buying a computer power supply, remember there are
two types, AT and the newer ATX. It is better to have the older AT style, as
this power supply will have a physical switch to turn it off and on.
If the power supply does not have a 20-pin connector (two rows of 10 side by side),
you don't have an ATX power supply. Also the ATX style usually has no AC power
switch. On the other hand, a true AT supply will have a 120V power switch
connected to it. And when an AT is switched on, the fan runs and it stays
on, whether there is a power load or not.
The newer ATX style has a "soft switch" (which allows the Windows
operating system to automatically turn the computer off),
as it relies on signals from the motherboard to power it off and on.
In order to turn "on" an ATX power supply, the large 20 pin connector
must have its green PS-ON wire (pin 14) tied
to the black COM ground wire (pins 13 or 15-17).
Note that pin 1 is the "square" pin, and pin 11 is directly across from pin 1.
Tying this green wire
to a black COM wire will turn the power supply permanently "on", so
you could install a physical switch between these two wires as a
power switch.
Also remember switching power supplies like the AT and ATX
are switch-mode power dependant on load.
This means that the power is switched on and off rapidly to meet the
load. If there is no load (nothing attached), the output power is switched off.
So using a DMM (digital multi-meter) alone to test the power supply output
voltages may not be enough draw to make the power supply turn on.
In either case, all you need to do is connect the power supply
to a wall plug (110 vac), and put aligator clips on the GND,
+5 vdc and +12 vdc. That's all you need to power up a Bally MPU
board on your workbench!
On a computer power supply, the best way to do this is to use
one of the plugs that connected to the computer's hard drive,
floppy drive, or CD ROM drive. There are usually at least
three of these 4 pin plugs on each computer power supply.
These plugs have two black wires, and one red and one yellow wire.
The two black wires are ground, the red wire is +5 vdc, and the
yellow wire is +12 vdc. I used some crimp-on male connector
pins and jammed them into the plug. Then I connected these to
aligator clips, which ultimately go to your MPU board.
Using a computer power supply on the workbench to
power a Bally MPU board.
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On the MPU board, the test points to connect the aligator
clips to are:
- TP5 = +5 volts (right next to the battery). Red power supply lead.
- TP4 = GND (opposite end of the board from the battery). Black power supply lead.
Don't get this confused with TP1, which is right next to it!
- TP2 = +12 volts (on the same side of the board as the battery; don't
get this confused with TP3, which is right next to it!) Yellow power supply lead.
- TP3 = +21.5 volts (right next to TP2). No power supply lead since neither
a computer power supply or a switcher supply this voltage. This assume this is
*not* a -133 MPU board. If a -133 (with a 1N4148 diode at R113, as used on
Granny and the Gators, Baby Pacman, & Grand Slam), temporarily convert R113
from a 1N4148 diode to a 2k ohm resistor.
Once you have your test fixture constructed, you can diagnose Bally MPU
problems with the flashing LED on the board easily. Instead of putting
the board back in the game to test it, just turn your power supply on
and count the flashes!
Warning!!
Be careful when you hook up the voltages to your MPU board. If you short
+12 volts to +5 volts (for example), you will probably destroy all the chips
on the MPU board! Also be careful when you hook up +12 volts to TP2. It is
VERY easy to short TP2 to TP3. This may damage the MPU board too! (Unlikely,
but let's not risk it). So be careful, and double check your connections before
you turn the power supply on.
Problems Using the Computer Power Supply.
The original linear power supply for the game powers on
with 5 volt very quickly. That is, within 50 miliseconds or so.
Remember the purpose of the MPU board's reset section is
to hold the U9 6800 pin 40 low for a short period of time, allowing the +5 volts
to stablize. Then the U9 6800 pin 40 goes high, which starts the
6800 running code out of U2/U6 ROMs.
The problem with *some* computer switching power supplies is they
take longer than 50 miliseconds to get the 5 volts up and stablized.
If you are using one of these slower switchers, a perfectly good MPU
board may not boot with that switching powe supply (that is, the MPU LED will be lock on).
Until you find a faster computer power supply, you can
get the MPU board started by shorting U9 6800 pins 39 and 40 for just
a moment (I use a small screwdriver to do this). This simulates
the reset section of the MPU board manually, holding pin 40 low for
moment. This should start the boot-up process and the MPU LED flashing.
To get the last flash from the MPU board, 20 to 25
volts DC is needed at test point TP3 on the MPU (or put a
temporary alligator jumper wire from chip U12 pin 3 to U14 pin 14).
This can be done by purchasing an inexpensieve 25 volt
transformer and bridge rectifier. I screwed this make-
shift power supply to a board for easier use.
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The Last LED Flash (missing voltage at TP3).
Using the above jig to power a MPU on your workbench
will NOT get the last MPU LED "flash" in the power-on sequence.
This happens because there is no +43 volts DC present (as used for
the solenoids) on the MPU board, which has a circuit to detect
this voltage. For most games, this means
only getting 6 of the 7 total flashes (for a working MPU). The exception to
this is Baby Pacman and Granny and the Gators, which only
get 5 of the 6 total flashes. And since the last flash is not achieved,
the board won't go into full attract mode.
There are *two* ways to solve this problem. The first is to trick
the MPU board into thinking the 43 volts is present. To do this, put a
temporary jumper wire on the MPU board, connecting chip U12 pin 3 to
chip U14 pin 14. This can be done easily with an alligator jumper wire,
connecting the top leg of resistor R23 (leg closest to chip U12) to the top leg of
resistor R17 (leg closest to TP3). This is certainly the easiest approach.
The other solution is more realistic, but involves some parts (a transformer and
a bridge rectifier). Radio Shack sells a 120 volt AC to 25 volt AC transformer
(#273-1366) for $6 that works well for this. They also sell a 25 amp
50 volt bridge (#276-1185) for about $2.70, which is also needed.
To wire this up, connect the
two black transformer wires that are together on one side of the transformer to a 120 volt power
cord. The remaining three wires (two yellow, one black) on the other
side of the transformer are the
output. Connect the two yellow wires to the AC terminals of
the bridge. The black (center tap) transformer wire you won't use.
The bridge should have a label signifying at least one AC
lead. The second AC lead is diagonal or across from the labeled lead.
The J4 connector of the MPU board. Notice
the TP3 and TP2 test points at the upper right
corner of this picture. The R113 resistor takes
the +43 volts from J4 pin 15 and lowers it to
+21.5 volts at TP3.
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Another lead on the bridge should be labeled "+". This is the
positive DC voltage output lead. The lead opposite or diagonal
to this terminal is the negative DC lead. Connect the "+" lead
to the MPU's test point TP3 (which is right next to TP2).
Connect the negative bridge lead
to ground (TP4) on the MPU board.
The output from the bridge will be about 25 volts DC.
43 volts DC is not needed because this connects 25 volts to
the MPU board's TP3 test point, which is looking for 21.5 volts DC.
What happens is the 43 volts DC comes from the rectifier board
and goes to MPU connector J4 pin 15. Then the 43 volts goes through
resistor R133, which lowers the voltage to 21.5 volts. Then a
"zero crossing" voltage detection circuit looks for that 21.5 volts.
If present, a working MPU board will flash the last time. If the voltage is missing,
there is no last LED flash.
So instead of supplying 43 volts to connector J4 pin 15, we just
skip resistor R133 and connect our 25 volt DC power supply directly
to TP3. It's pretty easy to get a 25 volt transformer, but getting
a 43 to 50 volt transformer is more difficult. The zero crossing
circuit will work fine if you supply 25 volts DC (instead of 21.5 volts)
to test point TP3.
The voltage supplied above with the transformer and bridge gives
25 volts DC to test point TP3. This DC voltage is NOT smoothed
with a filter capacitor! This is done for a reason. The original
Bally power supply doesn't filter this voltage, and for good reason.
The zero crossing circuit requires the DC voltage "ripple" to
work!
(Re-)Booting a MPU Board with the Test Fixture.
After connecting the test fixture to the MPU board, simply
turn the power supply on and count the LED flashes. To
re-boot the MPU board, simply short together (with a screwdriver blade)
pins 39 and 40 of the U9 CPU.
This will quickly reset the CPU, and the flash sequence will start over, without
having to turn the power supply off.
3b. When things don't work: Fixing the MPU (LED flashes
and the such).
Skip right to the LED Flash codes by clicking
here.
LED Flash Code Introduction and Assumptions.
I am assuming if your MPU board had any battery corrosion,
that you have fixed it (see the Removing the MPU Battery
and Fixing Corrosion section). Fixing a MPU board with corrosion
is like a dog chasing its tail; a never ending path of frustration.
Corrosion can cause intermittent problems. Take care of the corrosion first
before trying to fix a MPU board.
Fixing a Bally MPU board, generally speaking, is one of the easiest
game boards you will ever repair. The reason for this, is Bally uses
a "LED flash test". The green LED (light emitting diode) lamp is right
next to the battery on the MPU board. As the MPU board boots, it does
self diagnostics. For each diagnostic test the MPU board
runs, it flashes the LED when that diagnostic is complete. If a diagnostic
fails, the boot up process stops, and the LED stops flashing. There
are a total of 6 or 7 LED flashes during the boot-up process. This
makes determining MPU board problems fairly easy.
Preliminary Step: Power.
The Bally/Stern MPU boards need only 12 volts and 5 volts to start
booting (43 volts is needed later, but for now let's keep it simple).
Before starting the LED flash code diagnositics, check the power train.
Always check the end of the powerline first, the MPU board. It must have good
5 volts DC at TP5 and an unregulated 12 volts at TP2.
If the LED is lit solid and the MPU is not booting, it can be assumed that
the 12 volts is present (because 12 volts is needed to light the LED). So check for
5 volts DC at TP5, it should be in the 4.8 to 5.1 volt DC range.
Many times the MPU is locked only because the 12 or the 5 volts
are missing or low.
If the MPU LED is not lit, check TP2 for 12 volts DC. If 12 volts is there
but LED does not (never) lights, cross the two legs (on right side) of Q2
with a small screwdriver. This should turn-on the LED.
If it doesn't, assume that the MPU board's LED is bad and replace it.
If the 12 volts is missing from MPU TP2, forget about the
LED and go to the rectifier board and check for voltage there.
The following info applies mostly to games prior to Xenon (where
the power supply is in the backbox). But it can
be applied to the later games, especially when testing the 12 volt
and 5 volt DC circuits of the solenoid driver and MPU boards.
Different wire colors may be used in newer games,
but the test points (TP) and voltage readings are the same.
Check rectifier board TP3 for 12 volts. If missing, check the fuse
F3. Remove the 4 amp slo-blow and buzz it out with a DMM.
Check the fuse clips for damage or burns, as this is very common.
If still no 12 volts DC at TP3, check E11/E12 test points on the
rectifier board. These are the two AC inputs and should read
about 12 volts AC with your DMM connectors to both E11 and E12.
If no voltage check the wiring to the transformer or the transformer itself.
If the 12 volts AC is present at E11 and E12, then the bridge rectifier BR2
is open. If fuse F3 blows immediately at power-on, then the bridge rectifier
BR2 is shorted.
If there is 12 volts DC at TP3 on the rectifier board but no 12 volts
on the MPU board, likely it is just one wire causing the problem.
Check J3 pin 8 (orange wire) of the rectifier board, as it may be burnt.
It is a good idea to replace this connector pin as it handles the 12 volts
distribution and is often burnt.
Next the orange wire goes to the solenoid driver board
connector J3 pin 12. It makes a U-turn and heads back out J3 pin 11 and
goes to the MPU board (this is why there is often a jumper between the solenoid
driver board TP1 and TP3, to make sure this U-turn does not get cut).
At the Solenoid Driver, the 12 volts DC heads also heads
to the 5 volt regulator going through the big capacitor C23 (this smooths
out the raw 12 volts DC).
Often there is a problem with the begative side of cap C23 that
causes problems. The negative side of this cap goes back to the
Power Supply in a separate wire, independent of other ground circuits.
Even though all grounds end up at the same spot, this independent wire
helps limit line noise. It also can lead to some weird
problems like shutting down the MPU or causing massive resets.
This single white/brown return wire goes from the solenoid
driver from J3 pin 10 to the rectifier board J3 pin 17.
Note that these pin numbers at the rectifier board may
not the same the game you are working on. The
grouping of the pins at rectifier board connector J3 are often
swapped around between pins 1-4 and pins 14-20. These are all ground
returns and over the years perhaps the wires were moved. Keep this
in mind.
The point is if this ground
return wire from the solenoid driver board capacitor C23 to
the rectifier board gets cut, it will shut down the 5 volt regulator
and the MPU. The fastest way to do a check is to jump the left (negative)
side of the cap C23 to any ground in the backbox. If the game
comes up, you have found a problem with the white/brown wire.
You should now have +5 and +12 volts DC at the MPU board, and can
start diagnosing the MPU LED board flash codes.
First Step: Count the LED Flashes.
The first step in fixing a non-working game is to count
the LED flashes. On a working MPU board, when you turn
the game on, the LED should "flicker" (a very faint and
quick flash), and then flash seven times (only six times on
Baby Pacman or Granny and the Gators). If the board does
not do this, the internal diagnostics have determined
a problem. At this point you should remove the board
from the game, and hook it up to your test fixture (which
you made above in the Making a MPU Test Fixture
section). Working on your MPU board on a workbench is much
easier than trying to fix it, and then test it in the
game itself.
The Last Flash.
If you game does the initial flicker, and then follows with
all the flashes but the last flash (flash number seven, or flash
six on Baby Pac/Granny), check your +43 volt solenoid power F4
fuse on the rectifier board before proceeding. This last flash
verifies that the game has +43 volts for the solenoids. If it
doesn't (the F4 fuse is blown), the game won't boot and won't
finish the flash sequence.
No Flashes: the LED is Permanently On.
If you turn your Bally game on, and the LED stays on
continually, this is one of the hardest problem to
fix on these boards. A stuck on LED can be caused by
any (or all!) of the following:
- The reset circuit is damaged (after all, it's in the
battery corrosion area!) This includes transistors Q1 and Q2 (both 2N3904),
Q5 (2N4403), and diodes CR5 (1N4148 or 1N914) and VR1 (1N959B or 1N4738A).
- The program ROM (read only memory) at U6 is bad.
- The ROM jumpers are incorrectly set for the U6/U2 ROMs installed.
- The U9 CPU microprocessor is bad.
- The U11 PIA (peripheral interface adapter) is bad.
- ANY of the sockets for chips U6, U9, U11 are bad.
- The ground trace to U11, U6 or U9 are bad. U11 is especially
important to check the ground trace, as it's right in the corrosion
zone. And corrosion just loves to travel up the ground traces. Use a DMM
set to continuity to check ground at U11 pin 1 (and U11 pin 20 for +5).
Also check U6 pin 12 for ground (and U6 pin 24 for +5).
U9 pin 1,21 (gnd) is less of a problem as it's well outside the corrosion area.
The first and last two points are probably the most common problems.
Go "Bare Bones" (What to Remove for the first "Flicker").
To get the initial flicker out of the MPU board's LED,
you only need three chips on the MPU board. These three
chips are U9 (the CPU), U11 (PIA) and U6 ROM (except on
some Stern games, which also require the U2 and/or U5/U6 ROMs).
Remove all other socketed chips! Once you get the initial
flicker out of the MPU board, then you can re-install the
other removed chips.
The Reset Circuit.
If the reset circuit is damaged, the MPU board will never
start, and the LED will stay on at power up.
Since the reset circuit is in the "corrosion zone",
it is often damaged from battery corrosion.
The reset circuit holds pin 40 (reset) of the U9 CPU
low until +5 volts is "stable", and then sets pin 40 high
(telling the CPU it can start the boot up process).
While the reset section is holding pin 40 of the CPU low,
the LED will be on. This is one part of the initial "flicker" seen
when a working Bally board is first powered on.
Here's what to try first:
- With the MPU board OFF,
Put a logic probe or DMM set to DC volts
on pin 40 of the U9 CPU. The logic probe will be "low" (or the DMM at zero volts).
- Power the MPU board on.
- In just an instant, the U9 CPU Pin 40 should go "high" on the logic probe,
or about 4.75 to 5.5 volts on the DMM. Repeat this for
U9 pin 2, which also should also go high.
If the above happens, the reset circuit is probably working fine.
If pin 40 of the CPU is low and never goes high, there is a problem
with the reset circuit. Since pin 40 never goes high, the CPU will
never start the boot process, and the LED will stay on.
Here's some other stuff to try:
- With the MPU board powered on and pin 40 of the U9 CPU high (4.75 to 5.5 volts),
short the junction of resistors R1 and R3 to ground.
To do this, find the junction where resistors R1 and R3 connect together
(the right side of R1 is the junction of R1 & R3).
With the MPU board on, use a wire and short this junction to ground (TP4).
- U9 CPU pin 40 should now go low to zero to .5 volts while the R1/R3 junction is grounded.
The above procedure is simulating what the reset circuit is meant to do.
If shorting the junction of R1 and R3 does not pull U9 Pin 40 from high to low,
then there is a problem with the reset circuit.
Most likely there is a problem with Q1 (2N3904),
Q2 (2N3904) and/or Q5 (2N4403).
Replace them all (they are cheap!) and repeat the above procedure. Also check/replace
diode CR5 (1N4148 or 1N914). Finally check/replace diode VR1, which is a 1N959B (1/2 watt)
or 1N4738A (1 watt), 8.2 volts (note VR1 is mis-labeled in the manual as "1N9598").
If you still can't get U9 CPU pin 40 to go low, there is some other problem
in the reset circuit (corroded traces?).
Here are some other points to check. Turn the MPU board on and test:
- U9 pin 3 = 2.4 volts
- U9 pin 36 = 2.6 volts
- U9 pin 40 = 4.75 to 5.5 volts
- U9 pin 5 = 2.8 volts
If the above voltages check out, then the reset section is probably
working correctly. This means your problem probably lies with chips U6, U9 or U11
(or their sockets), or incorrect MPU board jumpers.
A Reset Trick (LED stuck On) - Adding a Capacitor.
If having problems with the reset (LED stuck on),
try shorting together (with a screwdriver blade)
pins 39 and 40 of the U9 CPU. This will manually reset the CPU, since
reset pin 40 gets set low by ground, pin 39.
Essentially, the screwdriver blade is doing what the reset does.
So if the flashes start and proceed, there is a problem with the reset
section of the MPU board.
It could be the +5 volts is not stablizing within the "window"
the CPU expects (about 50ms). To make the reset window longer,
try putting a 470 mfd electrolytic capactor in the reset section
(on the solder side of the MPU board).
Solder the positive leg of this cap to the collector (top leg)
of Q1. Then solder the negative leg of the cap to ground (the emitter
of Q1). This will increase the reset timing length. Now test the MPU board.
If the MPU board works and continues with the flashes, the +5 volts
was just not getting "stable" in the 50ms window (there could be
a power supply problem, probably with the large 12 volt C23 rectifying capacitor
on the driver board).
One note about this added reset capacitor. Since the 470 mfd cap
increases the reset timing (the time pin 40 of the CPU is held low),
the initial "flicker" may not longer be a "flicker". The LED will
stay on longer (because the reset is longer), making the "flicker"
more of a "flash".
Buy a Bally Reset Section Repair Kit.
Having problems with the reset section on your Bally board?
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
gone bad in the reset section. For a mere $10, or $4.50 (without a 5101 RAM chip),
this kit is well worth it. See Ed's web page at
www.greatplainselectronics.com
for more information. When buying the kit, install *all* the parts,
even if the originals "look good".
If for some reason the $4.50/$10 is too much money, here are the typical parts needed for
reset section repair:
- Q1,Q2 - Transistor, 2N3904
- Q5 - Transistor, 2N4403
- VR1 - Diode type 1N4738A, Zener, 8.2V (alternate for 1N9598)
- CR8 - Light Emitting Diode, Green.
- CR5,CR7 - Diode, Switching. 1N4148
- CR44 - Diode, Rectifier. 1N4004 (or better)
- C1,C2 - Capacitor, 820pF, Axial Ceramic.
- C5 - Capacitor, 4.7uF, Radial Tantalum.
- C3,C13,C80 - Capacitor, 0.01uF, Axial Ceramic.
- 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%
Using a Dallas/Maxim DS1811 in the Reset Section.
There is also another way to fix the reset section.
This involves using the new Dallas/Maxim Semiconductor D1811 reset chip (TO-92 package).
This single reset chip should replace a whole bunch of
the stock reset components on a Bally MPU (thanks to Neil for doing
the leg work on what can be removed).
This inexpensive Dallas device looks like a transistor, but is really a three leg chip in a TO-92
transistor package (I also show how to use this same reset chip on Gottlieb
System80 MPU boards in the Gottlieb System80 Repair Guide).
Click here or
here (PDF, more info)
for the specs on this chip. Cost is less than $1, and can be ordered directly
from Dallas/Maxim Semiconductor at
www.dalsemi.com
via their phone number 888-629-4642 (but orders must be faxed in at 408-222-7174).
Be sure to order the TO-92 package (part number DS1811-10), as this
chip also comes in a surface mount SOT23 package.
Interestingly, the new Alltek Systems replacement MPU board
(allteksystems.com)
also uses a Dallas-Maxim reset chip. The only difference is their
board uses a DS1233 (which is the same as the DS1811, except the
reset timing is 250ms, where the DS1811 is 150ms).
The Dallas DS1811 comes in three TO-92 flavors of
"normal reset threshold":
- DS1811-15 = 4.13v
- DS1811-10 = 4.35v
- DS1811-5 = 4.62v
Probably the best one to order is DS1811-10.
The DS1811 is installed with pin 1 going to /RESET (Q5's leg closest
to resistor R11), pin 2 to +5 volts, and pin 3 to ground.
If the MPU board boots fine by shorting pins 39 and 40 of the
U9 CPU, installing this part may be the "quick fix" to your reset problems.
Also the benefit of removing many of the stock reset components
on boards with battery corrosion certainly helps.
There is a side affect of the changed reset circuit:
Since the Dallas DS1811
increases the reset timing (the time pin 40 of the CPU is held low)
from about 50ms to 150ms,
the initial "flicker" may not longer be a "flicker". The LED will
stay on longer (because the reset is longer), making the "flicker"
more of a "flash".
Installing the Dallas DS1811.
Here are the steps to replace the Bally reset section with a
single Dallas DS1811 reset chip.
- Replace R11 with a *new* 2 watt, 82 ohm resistor.
- Remove Q1, Q5, R140, R138, R139, VR1, R112, R1, R2, R3.
- Put a jumper from the lower hole of R138 to the upper
hole of R139 (note "lower" and "upper" being relative to the MPU board in
its normally installed position in the game).
- Connect the reset pin of the DS1811 (bottom pin, as
the flat side of the DS1811 is towards connector J4)
to the collector hole of Q5 (the single left most hole
of Q5 closest to connector J4). Wait to solder this connection until the next step.
- Add a 1k ohm pull-up resistor from +5 volts to the DS1811 reset pin
(which is connected to the left most hole of Q5). In the picture below,
the banded side of CR5 was used to access +5 volts.
- connect the VCC pin of the DS1811 (the middle pin) to +5 volts,
which is the bottom right pin of Q5.
- Connect the GND pin of the DS1811 (the top pin) to ground,
which is the top right pin of Q5.
- Leave CR5, CR7 installed.
Replacing the reset section with a Dallas DS1811 reset chip. Picture by Neil.
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Note the 1k pull-up resistor is needed for additional current draw for all devices
needing reset. If not installed, the MPU board can be intermittent on powerup
because the DS1811 can't source enough current to bring the reset signal high
by itself.
As Neil explains,
replacing resistor R11 is a good idea. These carbon resistors
eventually heat up and break down, and once you replace the rectifier
circuit with better diodes, the leakage is smaller and that results in
around 14 volts on the 11.9 volt line. This is enough to push the stock
resistor out of spec. It will heat up and change resistance,
and in some cases will go open, which causes a reset. As long as R11 is a 2
watt resistor, it should be fine. If the current resistor is discolored or
of a carbon type, it should be replaced.
A "Good" U6: EPROMs, Masked ROMs, and Jumpers.
If the LED is stuck on,
next give yourself the advantage of knowing that at least the program jumpers
match the type of Game ROMs being used (EPROMs, Masked ROMs,
etc.). Jumper are discussed in the Game ROMs, EPROMs,
and Jumpers section below. Basically these jumpers tell the
MPU board what type, size, and how many game ROMs are being used on the
MPU board. Bally did this as a convenience factor; if you wanted
to use an older MPU board in a newer game (that had a larger program and
hence larger or more ROMs), you could. All you needed was to change
the jumpers. It also allowed you to use the board with EPROMs (erasable,
programable read only memory), or factory created "masked" ROMs. The
factory masked ROMs are black with numbers screened on them. These
are not re-programable, and must be used in the game they are
intended for. EPROMs on the other hand, can be re-programmed and
re-used (if you have an EPROM programmer, which costs about $150
and can connect to your computer).
An accurate jumper chart is mandatory here and a basic knowledge of
how to recognize the different types of ROMs is also a plus.
U6 is the program ROM chip which contains the code for the boot-up
diagnostics (and on some Stern games, U2 and/or U5/U6 ROMs are also required for the initial "flicker").
If you don't have a good U6, and don't have the MPU
jumpered properly for that U6/U2, the diagnostics can't even start
to run. If you don't have an EPROM programmer to make your
own U6 EPROM, contact Tom
Callahan and order the ROMs needed for your particular game.
Make sure you plug them into the sockets correctly (notch
oriented correctly) when you install them. Also make sure you
have the jumpers set correctly for the type of ROMs you are installing.
Don't Change the MPU board's ROM jumpers unless you have to!
If the U6/U2 ROM jumpers are incorrectly set on your MPU board,
this can cause a locked-on MPU board LED. For this reason,
I suggest not changing the MPU board jumpers until getting
the initial flicker from the LED. If the jumpers are changed,
TWO problems could exist instead of just one! If
not sure if the U6 ROM is good, try and install a known good ROM
of the same type (or test the U6 ROM in another game).
This way the board jumpers don't need to be changed.
Using 2532 EPROMs instead of 9332 Masked ROMs.
If the game in question is a later Bally game with 9332 masked
ROMs, these can be changed to 2532 EPROMs with NO jumper modifications!
This can be handy and convenient if the original black 9332 masked
ROMs need changing, but the repair person doesn't want to mess
with the jumpers.
A "Good" U9 and U11.
These two chips MUST also be good to get your MPU board to
even start to work. The diagnostics won't even start to run
if you don't have a good CPU chip at U9. Also a good PIA chip
at U11 is required.
If your LED is locked on, and the reset circuit is working (see above),
I would next invest in a new 6800 CPU for U9,
and a new 6821 PIA for U11. You can buy these for just a few dollars.
Get a couple extras of each chip. While you're at it,
get a few 5101 RAM chips too (as these go bad a lot on the MPU board).
What Chips are Required to Get the MPU "Unlocked"?
The only socketed chips that are required to get the MPU board
to do its first flicker, are a working U6 (program ROM), U9 (the CPU),
and U11 (a PIA). Of course this assumes the reset circuit is working
properly. All other socketed chips can be removed
until the board becomes "unlocked" and does its first flicker.
How Can I Ensure I have good U6, U9 and U11 Chips?
I keep a working MPU board around, and plug the unknown
chips (one at a time!) into the working MPU. Then I power the
MPU on and see if it still works. This works best for me,
but you may not have a good MPU spare laying around.
If you have no spare working MPU, make sure you buy some
new U9 (6800 CPU) chips and U11 (6820 PIA) chips.
They are inexpensive and worth keeping "in stock".
And get a set of known good EPROMS (U6/U2) too. You can buy these from
many sources if you don't have an EPROM programmer
Good Chip Sockets (replace the "closed frame" sockets!)
If the sockets for U6, U9 and U11 are "bad", nothing will
make the LED start flashing until this is fixed. If the sockets are
the closed frame brown or black sockets (closed frame means the
circuit board can not be seen under the socket),
or have the brand name "SCANBE" or "RS" impressed
into the sockets, replace ALL of them! These types of sockets are known
to be troublesome. Another approach to replacing these problem sockets
is to plug a new machine pin socket into the problem socket, then
plug the chip into the new socket. This is
a good temporary solution until you get the MPU board working.
Then you can later replace the old bad sockets with new machine pin sockets.
Using your DMM, buzz-out the chip legs to the under side of the MPU board
to make sure the sockets are good.
Note: do NOT get gold plated sockets! These react with the different metal in
the chip legs, and can cause intermittent problems. Also remember that U11
is in the "corrosion zone". This means this socket could have easily
been affected by battery corrosion.
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.
|
|
Re-seating the Chips.
Sometimes fixing a MPU board can be as easy as taking all the socketed
chips out, and re-seating them into their sockets. It's worth a try,
as it only take a minute (and costs nothing). Sometimes bad connections
can be rectified by doing this. Make sure when you plug the chips back
in, that ALL the legs go into the socket and that the chip notch is oriented
in the correct direction (a common neophyte error). Plugging a chip in
"backwards" usually destroys it. If re-seating the chips does work, this
usually means the sockets will need replacing.
If re-seating actually fixes something, this mean the socket in question
is BAD. No question about it, replace that socket.
Component layout on the Bally MPU.
|
|
Do I have the Right Jumpers/ROMs Installed?
As stated above, if the jumpers are set incorrectly for the ROMs
installed in the MPU board, the MPU LED will be locked-on. This happens
because the ROM code is what turns the LED off - if the MPU can't access
and run the ROM code, then the LED will never turn off and start its flash
sequence.
On the CPU chip U9 pin 5 is the VMA line (valid memory address), and
it should never be stuck HI or LOW (it "polls" the U6 ROM).
A bad U6 ROM can affect the CPU U9 pin 5's behavior.
The CPU's U9 Pin 5 behavior is controlled by U9, but tying it to a bad
or mis-jumpered U6 ROM can cause many problems.
So if you are confused about the ROM jumpers, try this:
Boot the MPU board with only U9 and U11 installed (all other
socketed chips removed). The LED will stay on, but using a logic probe check U9 pin 5.
It should be pulsing. Power down, add ROM U6 and repeat. If U9 pin 5 is now stuck high
or low, U6 is either bad, or you have the wrong jumpers.
The LED is Still Locked On.
If the U6, U9, U11 chips and sockets are known to be good,
the reset section tests good,
and the board is jumpered correctly, you should be getting
at least a initial flicker from the LED. The inital flicker
indicates these three chips are good, and that the MPU has
started its boot-up process (a good sign!) Remember, on some
Stern games, a good U2 and/or U5/U6 ROMs chip are also needed to get the
initial flicker.
If the reset section is working, get a head start and
put in your own "known good" U9, U6 and U11 (and re-jumper the board
if necessary). This will usually get at least a flicker out of the LED.
If the LED is still locked on, here's some other things to test:
Reset Section Components to Replace:
- If the zener diode VR1 (1N959B or 1N4738A, 8.2 volt) on the MPU board is bad,
the LED will remain on.
- If the reset transistors Q1 (2N3904) and Q5 (2N4403)
are damaged, the LED will remain on. As a general rule, it's
always a good idea to replace these inexpensive transistors.
- If diode CR5 (1N4148 or 1N914) is bad, the LED will
remain on.
- If transistor Q2 (2N3904) is bad, it could leave the LED on (regardless
of what the MPU is doing!)
After the Reset Section is Rebuilt, try this:
- If your CPU board has brown sockets, or sockets labeled
"SCANBE" or "RS", you may want to replace ALL the sockets.
These sockets are known to be problematic. An alternative
to replacement is to plug a machine pin socket into the
problem socket, then plug the chip into the new socket.
This is a good temporary solution until you have the MPU
board working.
- Measure the voltage at the CPU board. Even if you are
using your test fixture, measure the voltage right at the
chips to verify. The +5 line should be 4.8 to 5.2 volts DC.
Check the power at the required socketed chips (U6, U9, U11). This will tell
you if power is getting through the board to the chips
- U6, U2 (ROM): +5 = pin 24, GND = pin 12
- U9 (CPU): +5 = pin 8, GND = pin 1 or 21
- U10,U11 (PIA): +5 = pin 20, GND = pin 1
- U8 (5101): +5 = pin 22, GND = pin 8
- U7 (6810): +5 = pin 24, GND = pin 1
You don't really need to check the +12 at the board.
If the LED is lit, you know the +12 volts is already present.
- Using a logic probe, check U9 (CPU) pin 2 and pin 40. They
should be high. Pin 40 is the Reset line, and this pin will
start LOW at initial power-on (for about 50 ms), and then go HIGH. As you turn the power on,
the logic probe's low LED should light briefly, then the Hi LED
should turn on and stay on.
If there is no initial LOW followed by about 4.5 volts at pin 40, the "valid power"
reset circuit in the lower left corner of the board is at fault.
The reset section's job is to hold the CPU pin 40 low until the +5 volts stablizes,
and then allow pin 40 to go high to 4.5 volts. If pin 40 stays low, the board
will never reset, and the LED will stay locked on. Most
likely there is corrosion damage to transistors Q1 (2N3904), Q2 (2N3904), and Q5 (2N4403).
Also check diode CR5 (1N4148 or 1N914). Replace all of
these if you suspect them as bad. Or better yet, order a reset rebuild
kit from Ed (about $10) at
www.greatplainselectronics.com,
and rebuild the entire reset section.
- If U9 CPU pin 40 is high (about 4.5 volts), then
jump the junction of R1 and R3 (the right side of R1)
to ground. Now check U9 CPU pin 40 again.
This pin should be low (about .5 volts). This is simulating what the
reset section does at power-on. If jumping R1/R3's junction to ground
does not give .5 volts at U9 pin 40, there is still a problem with
the reset section. Try replacing the
reset transistors Q1 (2N3904), Q2 (2N3904), and Q5 (2N4403).
Also check the diode CR5 (1N4148 or 1N914). To do this, put your DMM
on diode setting. You should get a reading of .3 to .6, and reading
of null (zero) when the leads are reversed. Or again, install
one of Ed's reset section rebuild kits (which includes all the
reset parts needed).
- Using a logic probe, make sure chip U9 (the CPU), pins 3 and 36, 37
are "pulsing". These are the "clock" signals. If you don't have a
logic probe, put your DMM on these pins and you should get
about 2.5 volts (the average of the pulsing waveform).
If you don't have a pulse or about 2.5 volts, suspect chips
U15 (MC3459L or 74S37) and U16 (9602 or NTE9602). Also sometimes
the C14 and/or C15 (470 pf) capacitors have failed. However the most common cause
is a bad U15 (MC3459L or 74S37).
- Check that U9 (CPU) pin 2 is high (+5 volts). This is the Halt signal
on the CPU. If it's not HIGH, check for a broken or missing resistor
at R135 or a short on the J5 connector.
- Using a logic probe, check that U9 (CPU) pin 5 is pulsing (or use your
DMM and you should get about 2.8 volts). This is the VMA
(valid memory address), and is an output from the CPU. If it's not
pulsing, the CPU is not running! It could be a bad U9 chip, or some
fault on the address and/or data lines cause U9 to "crash". Watch U9 pin 5
on the logic probe after turning the power off and then back on. You should see it
pulse for a second or two before stopping. If any CPU output pin is shorted,
this can cause the CPU to crash.
Left: Chip U9 (CPU),
pin 3. Note pins 36, 37
will have the same
signal pattern too.
This is the clock signal.
|
Middle: Chip U9 (CPU),
pin 40 and pin 2. Should
be a straight line "high",
except initially at
power-on.
|
Right: Chip U9 (CPU),
pin 5. This is the Valid
Memory Address line.
|
|
|
|
- Trace the VMA signal through its path. Using a logic probe, test
the following path. You should get a pulsing signal at all points
while the game is in attract mode (or when the MPU is on the bench
in your test fixture):
- U9 pin 5 (VMA line on the CPU): Pulse
- U19 pin 8 (input to U19): Pulse
- U19 pin 9 (input to U19): HIGH
- U19 pin 10 (output from U19): Pulse
- U14 pin 11 (input to U14, about 1.3 volts measured with a DMM): Pulse
- U14 pin 12 (output from U14): High Pulse
- U15 pin 4 (input to U15): Pulse
- U15 pin 5 (input from U16 pin 10): Pulse
- U15 pin 6 (output from U15): Pulse
- U15 pins 1, 2 (input to U15 again; both pins tied together): Pulse
- U15 pin 3 (output from U15, about 1.8 volt measured with a DMM): Pulse
Tracing the above, you can see where the signal runs astray. Replace
the suspected component. U15 (MC3459L or 74S37) seems to be the
component that fails the most here, followed by U14 then U19.
Left: U9 (CPU) pin 5, and U19 pin 8.
|
Right: U19 pin 10, and U14 pin 11.
|
|
|
Left: U14 pin 12, and U15 pin 4
(U14's wave form is tighter)
|
Right: U15 pin 5 (only seen on a fully booted MPU).
|
|
|
Left: U15 pin 6, and U15 pins 1 and 2.
|
Right: U15 pin 3.
|
|
|
- Check U9 (CPU) address and data lines with your logic probe for
pulsing signals. This includes pins 9 to 20, 22-24 (address lines, pin
24 is only used if 2732 EPROMs installed), and pins 26 to 33 (data lines).
Note pin 21 is ground.
- If the PIA at U11 is bad (or its socket is bad), all
the above pulses can be present and acting correctly. Yet the LED will
still be stuck on. This PIA is right in the "corrosion zone",
so make sure the U11 socket and chip are in good shape.
- If C23 on the solenoid driver board is not filtering the full wave rectified DC volts
effectively, this can cause the MPU to lock and leave the LED on
(see Upgrading the Voltage Regulator/Solenoid Driver Board
for details on this).
- If Q20 (the +5 voltage regulator) on the Solenoid Driver board
is bad, the LED will remain on.
If you've gotten to this point, and the MPU's LED is still staying
lit, you may want to consider sending the board out for repair.
Strengthen the Reset Signal by Replacing Caps C14 and C15.
The two capacitors at C14 and C15 (470 pfd) should also be
replaced. If these capacitors are weak, the reset signal will not
be as crisp and strong. This is very apparent if you have a scope.
Was there Work Done on Chips U15 and U16?
If chips U15 (MC3459L or 74S37) or U16 (9602) were worked on, suspect problems.
Even though these chips are not directly involved in the reset circuit,
there are very fragile traces which travel underneath the
U15/U16 sockets. If someone replaced these chip and/or sockets,
these traces could be damaged.
Using a ohm meter and check for continuity on all of these
traces (this may require removing the U15/U16 sockets; always
replace these sockets with strip socket headers, so the
traces maybe seen and worked on easily in the future).
More on the RESET Signal and a Locked-on LED.
A major part of the reset circuit is transistor Q1, and there is an easy
way to test it. As we learned above, when the game is first turned
on, the reset line (pin 40 of the U9 CPU) goes low for just a moment,
then sticks high. You can similate a reset by shorting the
ground junction of resistors R1 and R3. This will force a reset
in a good MPU board. As you do this, watch pin 40 of U9 with your
logic probe. It should go low for a moment, then stick high.
If it doesn't, try replacing Q1 (2N3904). If Q1's collector doesn't
go to about 4 volts DC when R1/R3 junction is grounded, then Q1 is bad.
Q5 gets Cooked by R11, and the Game Re-boots Intermittently.
Another strange problem relates to transistor Q5 (2N4403). This
transistor is also part of the reset circuit (along with Q1),
and is located right below R11, an 82 ohm 2 watt power
resistor. The problem here is resistor R11 gets HOT, and is sometimes
touching Q5. The heat is transfered to Q5, and this can cause the
MPU board to suddenly stop running, and reboot the game.
To fix this, provide an air gap between Q5
and R11. You should also probably replace Q5 too. If you replace R11,
make sure you leave some "air" between R11 and the MPU board.
The Game only Starts up "sometimes".
If the MPU only starts up properly "sometimes",
replace Q1 and Q2 (both 2N3904), Q5 (2N4403), VR1 (1N959B or 1N4738A) and CR5
(1N4148 or 1N914). These transistors and diodes need to be in perfect
working order for the MPU to boot reliably.
LED Still Locked On: MPU Board Signals.
If having play problems with an otherwise working MPU,
check all the chip's
signals with a logic probe, and cross reference them to this
chart. If a signal is other than shown below, check the schematic. If it's
an input line to the chip, the device that feeds that pin is
probably bad. If it's an output line from the chip, the chip
itself is probably bad.
All the following signals are with the MPU board in "attract" mode,
and a MPU -35 loaded with Kiss 2732 EPROM's at U2 and U6.
Because these signals are with the game in attract mode, this
chart won't help much if your MPU is in some other state.
Key:
- H = Logic High (+5)
- L = Logic Low (GND)
- P = Pulse
- HP = High Pulse (signal is mostly high but pulsing)
- LP = High Pulse (signal is mostly low but pulsing)
- X = No signal
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U16 (9602) |
L 1 |
|
16 H |
|
U15 (MC3459) |
P 1 |
|
14 H |
|
LP 2 |
|
15 L |
|
| P 2 |
|
13 P |
|
H 3 |
|
14 LP |
|
| P 3 |
|
12 P |
|
P 4 |
|
13 H |
|
| P 4 |
|
11 P |
|
H 5 |
|
12 P |
|
| P 5 |
|
10 P |
|
P 6 |
|
11 H |
|
| P 6 |
|
9 P |
|
P 7 |
|
10 P |
|
| L 7 |
|
8 P |
|
L 8 |
|
9 P |
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U20 (4502) |
P 1 |
|
16 H |
|
U17 (7400) |
P 1 |
|
14 H |
|
P 2 |
|
15 L |
|
| P 2 |
|
13 P |
|
P 3 |
|
14 P |
|
| P 3 |
|
12 P |
|
L 4 |
|
13 HP |
|
| P 4 |
|
11 P |
|
LP 5 |
|
12 HP |
|
| P 5 |
|
10 P |
|
P 6 |
|
11 LP |
|
| P 6 |
|
9 P |
|
LP 7 |
|
10 P |
|
| L 7 |
|
8 HP |
|
L 8 |
|
9 LP |
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U18 (4049) |
H 1 |
|
16 X |
|
U19 (4011) |
HP 1 |
|
14 H |
|
P 2 |
|
15 P |
|
| HP 2 |
|
13 P |
|
P 3 |
|
14 P |
|
| P 3 |
|
12 P |
|
P 4 |
|
13 X |
|
| P 4 |
|
11 P |
|
P 5 |
|
12 P |
|
| H 5 |
|
10 P |
|
P 6 |
|
11 P |
|
| HP 6 |
|
9 H |
|
HP 7 |
|
10 H |
|
| L 7 |
|
8 P |
|
L 8 |
|
9 L |
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U14 (4049) |
H 1 |
|
16 X |
|
U12 (555) |
L 1 |
|
8 H |
|
P 2 |
|
15 LP |
|
| HP 2 |
|
7 P |
|
P 3 |
|
14 HP |
|
| HP 3 |
|
6 P |
|
P 4 |
|
13 X |
|
| H 4 |
|
5 H |
|
HP 5 |
|
12 P |
|
HP 6 |
|
11 P |
|
P 7 |
|
10 HP |
|
L 8 |
|
9 P |
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U2 (ROM) |
P 1 |
|
24 H |
|
U6 (ROM) |
P 1 |
|
24 H |
|
P 2 |
|
23 P |
|
| P 2 |
|
23 P |
|
P 3 |
|
22 P |
|
| P 3 |
|
22 P |
|
P 4 |
|
21 P |
|
| P 4 |
|
21 P |
|
P 5 |
|
20 P |
|
| P 5 |
|
20 P |
|
P 6 |
|
19 P |
|
| P 6 |
|
19 P |
|
P 7 |
|
18 L |
|
| P 7 |
|
18 P |
|
P 8 |
|
17 P |
|
| P 8 |
|
17 P |
|
P 9 |
|
16 P |
|
| P 9 |
|
16 P |
|
P 10 |
|
15 P |
|
| P 10 |
|
15 P |
|
P 11 |
|
14 P |
|
| P 11 |
|
14 P |
|
L 12 |
|
13 P |
|
| L 12 |
|
13 P |
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U7 (6810) |
L 1 |
|
24 H |
|
U8 (5101) |
P 1 |
|
22 H |
|
P 2 |
|
23 P |
|
| P 2 |
|
21 P |
|
P 3 |
|
22 P |
|
| P 3 |
|
20 P |
|
P 4 |
|
21 P |
|
| P 4 |
|
19 P |
|
P 5 |
|
20 P |
|
| X 5 |
|
18 P |
|
X 6 |
|
19 P |
|
| P 6 |
|
17 H |
|
P 7 |
|
18 P |
|
| P 7 |
|
16 P |
|
P 8 |
|
17 P |
|
| L 8 |
|
15 P |
|
P 9 |
|
16 P |
|
| P 9 |
|
14 P |
|
P 10 |
|
15 P |
|
| P 10 |
|
13 P |
|
P 11 |
|
14 P |
|
| P 11 |
|
12 P |
|
P 12 |
|
13 P |
Chip |
Pin/Signal |
|
Chip |
Pin/Signal |
U10 (6820) |
L 1 |
|
40 H |
|
U11 (6820) |
L 1 |
|
40 HP |
|
P 2 |
|
39 HP |
|
| HP 2 |
|
39 LP |
|
P 3 |
|
38 HP |
|
| H 3 |
|
38 HP |
|
P 4 |
|
37 HP |
|
| P 4 |
|
37 HP |
|
HP 5 |
|
36 P |
|
| P 5 |
|
36 P |
|
P 6 |
|
35 P |
|
| P 6 |
|
35 P |
|
P 7 |
|
34 H |
|
| P 7 |
|
34 H |
|
P 8 |
|
33 P |
|
| P 8 |
|
33 P |
|
P 9 |
|
32 P |
|
| P 9 |
|
32 P |
|
HP 10 |
|
31 P |
|
| H 10 |
|
31 P |
|
HP 11 |
|
30 P |
|
| H 11 |
|
30 P |
|
HP 12 |
|
29 P |
|
| H 12 |
|
29 P |
|
HP 13 |
|
28 P |
|
| H 13 |
|
28 P |
|
HP 14 |
|
27 P |
|
| H 14 |
|
27 P |
|
HP 15 |
|
26 P |
|
| L 15 |
|
26 P |
|
HP 16 |
|
25 P |
|
| H 16 |
|
25 P |
|
HP 17 |
|
24 P |
|
| H 17 |
|
24 P |
|
LP 18 |
|
23 P |
|
| L 18 |
|
23 P |
|
LP 19 |
|
22 P |
|
| H 19 |
|
22 P |
|
H 20 |
|
21 P |
|
| H 20 |
|
21 P |
Chip |
Pin/Signal |
U9 (6800) |
L 1 |
|
40 H |
|
H 2 |
|
39 L |
|
P 3 |
|
38 L |
|
HP 4 |
|
37 P |
|
P 5 |
|
36 P |
|
H 6 |
|
35 L |
|
L 7 |
|
34 P |
|
H 8 |
|
33 P |
|
P 9 |
|
32 P |
|
P 10 |
|
31 P |
|
P 11 |
|
30 P |
|
P 12 |
|
29 P |
|
P 13 |
|
28 P |
|
P 14 |
|
27 P |
|
P 15 |
|
26 P |
|
P 16 |
|
25 LP |
|
P 17 |
|
24 P |
|
P 18 |
|
23 LP |
|
P 19 |
|
22 P |
|
P 20 |
|
21 L |
The LED is Always OFF, and Never Comes On.
This can be caused by a lack of +12 volts getting to
the LED, or the LED could be dead. A dead LED happens quite a bit actually.
But first trace the +12 volts:
- TP2: should have +12 volts.
- R29: should have +12 volts on both sides of this 1/2 watt 470 ohm resistor.
- Q2: should have +11 volts on the leg closest to U11 (PIA). <-- CLAY CHECK THIS.
- Q2: Cross the two legs that are next to each other with a screw driver.
The LED should come on.
If +12 volts is at the above three points (or at least two of them),
the LED is probably bad. If you have
the above voltages, cross the two adjacent legs of Q2 together with
a screw driver. This should light the LED. If it doesn't, and the above
voltages exist, replace the LED.
Ok, the MPU's LED "Flickers": What's Next?.
At this point you have an "unlocked" MPU board. By
"unlocked" I mean you get the initial LED flicker upon power-on.
This tells us that U6, U9 and U11 are good, and the CPU is
"running". Now the MPU will test the other components on the
board. So at this point, you should have all the other socketed
chips like U7, U8, U10, U2, etc (if you removed them) back in the board.
The U6 ROM will continue to run its diagnostics on the other
components on the MPU board and will FLASH when each of its
tests are COMPLETED. What follows is a description of these
flashes (or lack of them), and what they mean.
The MPU Diagnostic LED Flash Sequences Explained.
Introduction: The following LED "flash" sequences are indications to
the user that the MPU board's components are being tested, and passes these tests. The
number of flashes counted can determine very precisely what MPU board component
has failed (1977-1984 Williams pinball owners wish they had it this good!)
People familiar with repairing Bally MPU boards are indeed very thankful of
these tests, as most often they identify the exact problem on the MPU board.
Remember, the indication of a particular flash means the part being tested
passed. That is, if a MPU board boots with just a flicker and then two LED flashes,
this mean the reset section and chips/sockets U6/U9/U11 are good (the flicker indicates
they passed), ROM chips/sockets U1 to U6 are good (the first flash indicates they passed),
and the U7 RAM 6810 is good (the second flash indicates it passed).
Since no third flash was seen, this means the item being tested at the third flash
(the 5101 RAM at U8 or its socket) did not pass the test, and therefore no third
flash was seen. At this point, the boot-up program locks up, and will
not continue testing the MPU board until chip U8 (the third flash test item) is fixed.
Of course if the MPU board's LED locks on at boot up with no flashes, this means (as
discussed above) that the reset section and/or chips/sockets U6/U9/U11 are bad. At this
point, I am assuming the LED is not locked on, and that the reset section and
chips/sockets U6/U9/U11 are good (basically that the MPU board at least gives the
first LED "flicker").
1st Brief Flicker Completed:
The Fakers Guide: If the LED briefly flickers on power-up,
the CPU chip has booted and found the startup code in ROM U6, and is
starting to execute startup/test program in ROM U6.
So U6 (ROM), U9 (CPU), U11 (PIA),
the reset components, and +5 volts DC are good (remember some Stern games
also require the U2 and/or U5/U6 ROMs for the first flicker). If the LED locks on, one of these components
(or some other supporting components such as the MPU's Q1, Q2, Q5, VR1, or
C23, Q20 on the solenoid driver board) are bad (see above).
Also the traces connecting these components together could be bad (battery corrosion!)
Techno Guide: On power-up, the U9 CPU chip requires +5 volts DC be applied
before the reset line is allowed to swing from 0 to +4.8 volts. It also requires
the presense of a two-phase, non-overlapping clock pulse. If these conditions are
met, and if the U9 CPU chip itself is good, the LED on the MPU board briefly
flickers.
The brief flicker indicates the operation is proper. The MPU has gone out to
memory and obtained the starting address of the self-test from memory.
The flicker indicates that it then went to that address in the U6 ROM and started to
execute the self-test program in the U6 ROM.
The Valid Power Detectors circuit on the U9 CPU works with the +5 volts DC
regulator Q20 on the solenoid driver board. This prevents the reset line
from going high until +5 volts DC is proper at the U9 CPU chip. Q20 is
supposed to go into regulation when +7.5 volts DC is applied to its input.
This means that when the game is turned on, and a sufficient time (milliseconds)
has passed so that C23 on the solenoid driver board has charged, Q20 switches
into regulation. This supplies +5 volts DC to the MPU board.
Q1 on the MPU board (in the valid power detector circuit) does not allow
the CPU chip to turn on immediately. The zener diode VR1, in series with the
base of Q1 delays application of the reset voltage until C23 charges. At
this point, Q1 and Q5 on the MPU board go into conduction, and the reset
line at the MPU is caused to go high. Only then is the U9 CPU chip "on".
The importance of the Valid Power Detection circuit can be appreciated
when the following fact is known; should the reset line be allowed to go
high before the +5 volts is applied and proper, or should the +5 volt
supply fail and go out of regulation, the U9 CPU chip can jump out of
the program. The reason this happens is that the U9 CPU goes out to the
program memory bank U1-U6 for instructions. The logic levels are wrong
because the +5 volts is not proper. The MPU misinterprets the data,
jumps out of the program, and executes this misinterpreted program!
The U9 CPU is now like a train that has left the tracks, and it can end up
anywhere. The difference is that a train will eventually stop. But the
U9 CPU may continue as long as the clock circuit continues to run.
If the U9 CPU jumps out of the program, it is said to be in "run away".
While it is mis-interpreting the program, it invariably overwrites
the Bookkeeping function in U8 and the scratch pad RAM. An indication
of a "run away" would be false data in bookkeeping. Probable
cause is a faulty Q20 or C23 (or both) on the solenoid driver boared,
or a leaky zener diode VR1 on the MPU board.
First Flash Completed:
The Fakers Guide: flash number one means
ROM U1 to U6 are good.
No first flash means one (or more) of the game
program ROMs U1 to U6 are bad. Could be a mis-jumpered board,
or a bad ROM chip at U1 to U6, or a bad ROM socket at U1 to U6.
Techno Guide: the U9 CPU chip next goes out to the program
ROM's (read only memory) U1 to U6. It tests each chip in the
bank, in accordance to how the MPU board is jumpered. When it
finds the bank is correct, it flashes the LED for the first
flash. A fault in the U1 to U6 ROM chips is indicated by the
absense of the first flash.
The U9 CPU tests each ROM chip's function like this: in a game
with ROM chips U2 and U6 (typical), the CPU first goes to
U2. It fetches the first byte in U2, and adds it to the
second byte in U2. It will add to this sum the third byte
in U2. This continues until all bytes in the chip have been
added up. If the sum of all the bytes is "0000 0000", the U9 CPU
proceeds to U6 and repeats this process. If U6 has a sum of
"0000 0000", the U9 CPU causes the LED to flash the first
time. Fault in either U2 or U6 is indicated by the absence
of the first flash.
The contents of each ROM chip have byte locations called checksums,
reserved for this test routine. There is one checksum byte reserved in each
512 bytes of ROM memory. The game programmer at Bally must insert a
btye with the proper value in each checksum byte location to force
each 512 byte checksum to equal "0000 0000".
During the life of an electronic game, if a ROM chip U1 to U6 fails
by so much as a single bit, it will be detected during this CPU test.
The CPU will not continue until the defective ROM chip is
replaced.
Second Flash Completed:
The Fakers Guide: a second flash means
the 6810 RAM at U7 is good.
No second flash means U7 (6810) or its socket are bad.
Techno Guide: The U9 CPU chip goes out to the U7 RAM and
erases the contents of the first byte (U7 is a 128 byte scratch
pad memory). It then tries to read back the word "0000 0000" (indicating
erased). If it can read it back, it adds "1" and continues. 256 tries
later, it writes the word "1111 1111". If it can read it back, it has
determined that the first byte in U7 is good. It repeats this
process for each of the 128 bytes of RAM in U7, one at a time. If at
the end of this 256 x 128 (=32,768) tests, each time the CPU writes,
it can read the same word back, the CPU cause the LED to flash
a second time.
Note the pause between the first and second flashes. This is the CPU
doing 32,768 tests to the RAM at U7 and repeats the process.
Third Flash Completed:
The Fakers Guide: a third flash means the
U8 5101 RAM is good. No third flash means U8 (5101) or its socket
is bad.
Techno Guide: The U9 CPU goes out to U8 (CMOS 5101 RAM) and
makes a copy of the contents of the first half byte. It does this
because U8 is battery supplied, non-volatile memory where the
bookkeeping functions are stored. It then erases the contents of
the first half byte, and tries to read back the word "0000 xxxx".
If it can read it back, it adds "1" to the previous word (giving
"0001 xxxx"). It continues to write and read until it reaches
the word "1111 xxxx". When this is done successfully, the CPU
restores the original contents to the first byte located in U8. It then
makes a copy of the contents of the second byte, and repeats the
process. It does this for the entire 256 bytes, one at a time. If at
the end of the 256 x 16 (=4096) test, each time the CPU writes and
reads the same word correctly, the CPU caused the LED to flash
a third time.
Since the 5101 U8 RAM is in the "corrosion zone", here is a quick
check of the U8's connection to other components. This will help
determine if the U8 socket is bad. (Note the letter/number in parends
is the address, or data, or chip enable number.)
- U8 pin 1 (A3) - U7 pin 20, U6 pin 5
- U8 pin 2 (A2) - U7 pin 21, U6 pin 6
- U8 pin 3 (A1) - U7 pin 22, U6 pin 7, U11 pin 35
- U8 pin 4 (A0) - U7 pin 23, U6 pin 8, U11 pin 36
- U8 pin 5 (A5) - U7 pin 18, U6 pin 3
- U8 pin 6 (A6) - U7 pin 17, U6 pin 2
- U8 pin 7 (A7) - U7 pin 15, U6 pin 1, U11 pin 24
- U8 pin 8 - Ground
- U8 pin 9 (D10)*- U7 pin 6, U6 pin 14, U11 pin 29
- U8 pin 10 (D00)*- U7 pin 6, U6 pin 14, U11 pin 29
- U8 pin 11 (D11)@- U7 pin 7, U6 pin 15, U11 pin 28
(* U8 pins 9&10 shorted together)
(@ U8 pins 11&12 shorted together)
|
- U8 pin 12 (D01)@- U7 pin 7, U6 pin 15, U11 pin 28
- U8 pin 13 (D12)*- U7 pin 8, U6 pin 16, U11 pin 27
- U8 pin 14 (D02)*- U7 pin 8, U6 pin 16, U11 pin 27
- U8 pin 15 (D13)#- U7 pin 9, U6 pin 17, U11 pin 26
- U8 pin 16 (D03)#- U7 pin 9, U6 pin 17, U11 pin 26
- U8 pin 17 (CE2) - Q5 rt upper leg, U9 pin 40, U11 pin 34
- U8 pin 18 (OD) - U18 pin 6
- U8 pin 19 (CE1) - U17 pin 8
- U8 pin 20 (R/W) - U7 pin 16, U11 pin 21, U9 pin 34, U18 pin 7
- U8 pin 21 (A4) - U7 pin 19, U6 pin 4, U11 pin 22
- U8 pin 22 (Vcc) - C13 left leg, R12 upper leg, CR5 lower leg
(@ U8 pins 11&12 shorted together)
(* U8 pins 13&14 shorted together)
(# U8 pins 15&16 shorted together)
|
If all the U8 RAM lines ring out as described above, and
the 5101 U8 RAM is known "good", yet only two LED flashes
are received, next replace U19 (4011). This often fixes
a stubborn two-LED-flash MPU board.
Also be aware of the speed of any replacement 5101 RAM.
A too-slow 5101 will may pass the initial boot-up LED code test,
but can cause wack score display behavior.
Turns out a bad 5101 RAM or one that is too slow will not
keep up with the CPU's demand for accessing the display data.
Here's a list of 5101 RAM speeds:
- PCD5101P : 150nS (Philips)
- 5101-1 : 450nS
- 5101L-1 : 450nS
- 5101-2 : 450nS
- 5101L-2 : 450nS
- 5101 : 650nS
- 5101L : 650nS
- 5101-3 : 650nS
- 5101L-3 : 650nS
- 5101-8 : 800nS
The Phillips brand of 5101 is the best, as it's the fastest and will work
in all Bally/Stern MPU board applications.
Sterns MPU-200 need 450ns or faster RAM, Bally MPU -35/-17 need 650ns or faster.
So you can see that some 5101 RAM just won't work properely in Bally or Stern
MPU boards.
Fourth Flash Completed:
The Fakers Guide: a fourth flash means the U10 PIA (6821) is good.
No fourth flash means U10 (6821 PIA) or its
socket are bad. Or battery corrosion had broken a trace going to U10.
Or the chip leading to U10 is bad, which is U20 (4502).
Techno Guide: The U9 CPU chip now tests the first 6821 PIA
chip. There are two of these chips on the MPU board, which are
identical and interchangable. The test for both is the same.
To determine if a PIA chip is good, the U9 CPU does the following:
- The CPU accesses, by means of input RS0, RS1, CS0, CS1 and CS2
each of the two full byte registers used to store the port initialization
information. If does this, one register at a time. After it completes
the first register, it repeats for the second. It goes through 256
tests similar to that used to check each byte in U7 (second flash). If
each time the CPU writes a word into the register, it can read the same
word back, it continues to test until completion.
- The CPU accesses, by means of input RS0, RS1, CS0, CS1 and CS2,
each of two full byte registers used as data output registers when
PA0 to PA7 and PB0 to PB7 are used as outputs. It does the
same type of test on each register as described just above. Again if
no faults are found, the test is continued until completion.
- The CPU then accesses, by means of input RS0, RS1, CS0, CS1 and CS2,
the two ports CA2 and CB2. The port is initialized as an output. The port
is then written into to see if it can store a "1" and then a "0".
A total of 4 x 256 + 4 (=1028) test steps are required to test the
PIA chip. However, there are internal buffer amplifiers used with the
PB0 to PB7 output registers and CB2 port register which can not be tested
by the CPU. Access is only to the register; if the buffer is open, it does
not interfere with the registers ability to be written into and read
from by the CPU. It is this uncertainity that reduces the accuracy of
these test to 99.5%.
Also check and make sure that the MPU connector J1 and the lamp
driver connector J1 are not mixed up! These two connectors are about 4 inches
apart, and are keyed the same. If only three MPU LED flashes
are seen, this problem can also sometimes show the score displays
with an '8' or a '9' in the hundreds place.
Also I recently fixed a game (Bobby Orr Power Play)
where sometimes it would not get the fourth MPU flash,
but sometimes it would get all seven. If it did boot, the score displays would
flicker and only show some of the six digits.
The problem was a trace going to U10 on the component side of the MPU
right near the battery that was intermittent from corrosion.
After I cleaned up the corrosion (sanded and neutralized) and repaired
the broken trace (it was obviously open after sanding), the MPU booted and
the game worked correctly.
Fifth Flash Completed:
The Fakers Guide: a fifth flash means the U11 PIA (6821) is good.
No fifth flash means U11 (6821 PIA) or its
socket are bad. Note the flipper enable relay
will usually click on/off at about the fifth flash.
The lack of a fifth flash could also be a bad resistor
connecting to U11 like R134. Another issue could be a bad score display,
which can cause the MPU board to stop during the 5th LED diagnostics.
Disconnecting all the score displays (power off), then reconnecting
them one at a time (power off) and rebooting can help identify a bad display
that is dragging down the fifth MPU LED flash.
Techno Guide: Same test is performed on U11 as was performed
on U10. See above.
Sixth Flash Completed*:
The Fakers Guide: a sixth flash means the PIA at U11 (6821) and
the U12 timer (5550 chip is good. No sixth flash means either PIA U11 (6821)
or its socket is bad, or the U12 (555) timer is bad.
Lack of the 6th flash (five flashes only) can also mean a problems with
the zero-crossing detector. Often this is
the MPU board's R113 resistor (2k ohm, near the J4
connector) is open. This resistor takes the 43 volt DC coil power to
the zero-crossing detector circuitry and normally runs hot. Hence it
may eventually go open, so check it if only 5 flashes from the LED are seen.
Thanks to Ray J. for this tip.
Techno Guide: The U9 CPU chip monitors PIA2, port CA1 (U11). If
transitions from high to low are detected, the CPU decides the Display
Interrupt Generator is working. If U12, a 555 timer, or any associated circuit
component fails, the CPU will not flash the LED the sixth time.
* Note on Baby Pacman and Granny and the Gators, this flash step
is skipped and not tested.
Seventh (Last) Flash Completed**:
The Fakers Guide: Getting the seventh flash means the
CPU board has passed all self-tests. After the 7th flash, the LED
should have a very dim glow to it (this "dimness" occurs because
the game is strobing the switches), and the game should be in 'attract' mode.
No last LED flash generally means
there's no +43 volts DC for the solenoids (power transformer fuse F4 is
probably blown), PIA U10 (6821) or its socket are bad, or U14 is bad.
Remember the 7th flash is looking for 43 volts (or 6 volts AC in the case
of Baby Pac's last flash) on the MPU board. Note this test for voltage is performed on Baby Pac too
(the prior flash step is skipped, giving Baby Pac a total of 6 LED flashes).
This is done thru PIA U10's CB1 port. The PIA is looking for the zero-cross
of the 43 volts (or 6 volts for Baby Pac). If 43 volts is not present (rectifier
board F4 fuse blown), the last flash will not occur.
If the game locks_up after the 7th flash, try unplugging
the sound card and reboot. If it then works check the isolation power diode CR3
on the sound card - sometimes this bad diode on the sound board can lower the 43 volts
enough to stop the MPU board's 7th flash (Star Trek comes to mind).
Also Check the solenoid driver board cap
C23 is in good condition. There is also a chance the 555 timer chip and/or C17 could be
bad on the MPU board.
The 43 (or 6) volts can be "faked" and not supplied
(for example if you are booting the MPU board on the work bench),
and the last LED flash can happen. Just connect the top leg of resistor R23
(leg closest to chip U12) to the top leg of resistor R17 (leg closest to TP3)
using an alligator test lead.
Techno Guide: The U9 CPU chip monitors PIA1 port CB1 (U10). If
transistion from high to low are detected, the CPU decides that the
zero crossing detector is working. If U14 fails and the CB1 line is stuck
high or low, the test will also fail. The zero crossing detector circuit
input is the +43 volts DC line that is used for the solenoids. If the fuse
in that line (F4 on the power transformer module) is blown when the game
is turned on, the CPU will not flash the LED the seventh time.
** Note on Baby Pacman and Granny and the Gators there is no 7th LED flash.**
These games only had six flashes instead of seven. The easiest way to
determine if the MPU board is a -133 designed for Baby Pac/Gators and 6 flashes is to
look at the J4 connector (lower left corner) around pin 19. Between L1 and
L2 (the very large inductors that look like 2 watt resistors) is either
a diode (cr52) or a resistor (r113). If it's a diode, this is a -133 MPU
board and there will only be 6 flashes. If it's a resistor, it is a -35
or -17 MPU board and there should be 7 flashes.
Converting the -133 MPU to a -35 MPU is very easy do.
Just replace the 1N4148 diode at CR52 with a 2k ohm 1/4 watt resistor.
New EPROMs will need to be burned too of course
For more information on the -133 MPU board see here.
Game Initialization.
The U9 CPU chip now initializes the two PIA's U10 and U11, assigning
to each port its role as either an input or an output, as required.
It then clears out U7 (6810 RAM). Now the CPU takes a picture of the
settings of fixed switches S1 to S32 on the MPU board. It stores this
"picture" in memory in chip U7. The CPU next jumps to a routine which
turns on the "Game Over" feature light, lights the "Ball in Play"
light, and the "Credit Indicator" light if there are credits stored
in memory. It resets the drop targets and activates the saucer kickers
or any kicker associated with a playfield device that can trap
the ball and keep it out of the outhole. It then energizes the coin
lockout solenoid to allow the game to accept coins (unless the credit
maximum was met). Playfield and backbox feature lights
associated with and appropriate to animation effects are turned on.
With the game tested and initialized, the CPU now divides its time
between monitoring momentary switches for closure (coin switch, credit
button) and updating displays (lamps and score registers).
Problems/Solutions with the Seventh Flash.
Of course first verify that the MPU board is *not* a -133 model
with Baby Pacman or Granny and the Gator EPROMs (hint: if
U2 and U6 are a 2732 and 2532, suspect a -133 MPU board).
A few paragraphs above describes how to tell if it is a -133 MPU board.
If fuse F4 is blown on the solenoid board, the seventh flash
will not occur. But what if there is a problem on the playfield which
is forcing this fuse to blow (stopping the final LED flash on the MPU board,
hence stopping your MPU diagnostics)?
The easiest way to deal with this is to remove the solenoid connectors
from the solenoid driver board to the playfield. These connectors are
on the left side of the solenoid driver board, and the one connector at
the bottom right of the board too. This should allow the F4 fuse to be replaced,
and the completion of the MPU booting process.
To help find the playfield coil that is causing the F4 fuse to blow,
replace the connectors one at a time on the solenoid driver board (with the game off), and reboot
the game. This will help issolate the bad coil.
Another thing to try: remove the under-the-playfield coil fuse, and
replace fuse F4. If F4 does not blow, then one of the coils under
the playfield is somehow shorted or staying energized (and blowing
the solenoid driver F4 fuse). If fuse F4 still blows, there is either
a problem with the backbox knocker, or the cabinet coin door lockout
coil, the solenoid bridge rectifier (on the rectifier board), or the rectifier board's varister.
Also try removing connectors J1 and J3 from the rectifier board
(this moves the solenoid power back a step further, not allowing it to get any further
than the rectifier board).
Replace fuse F4 on the solenoid driver board, and turn the game on. If the fuse still blows,
the solenoid bridge rectifier (on the rectifier board) or the rectifier board's varister
is probably at fault.
If it is a coil under the playfield, check the coils to see which one energizes when
the game is powered on. Or disconnect a wire on each solenoid, and re-attach each wire,
one at a time, until the fuse blows. At this point it could be the coil, coil diode,
or coil driver transistor at fault.
Still No Seventh Flash - Other Things to Check.
First check TP3 and make sure there is 21 volts DC (of
course this assumes fuse F4 is not blown on the solenoid board).
If there is still no seventh flash, here are some other things to check.
Remember all the components mentioned
below are in the battery corrosion area.
- Check resistor R17 (150k).
If this resistor goes open, or is not making good contact
the circuit board, there will be no 7th flash. This resistor
commonly fails.
- Check resistor R16 (2k).
- Check resistor R18 (1.5 meg).
- Check diodes CR52 and CR49 (1N4148 or 1N914).
- Check the IRQ line (U9 pin 4 to U10,U11 pins 37,38) and
resistor R134 (4.7k) which ties the IRQ to +5 volts.
If there is still no seventh flash, the last thing to check is chip U14 (4572).
After the seventh flash the bally mpu enables the IRQ line. If the IRQ line is
broken, the will restart over and over.
Faking the 7th Flash.
If you are diagnosing a Bally MPU on the bench and don't have a 43 volt
power supply, there is a way to fake the MPU board into doing the 7th
flash. This may also be useful if all other things have been tried
and there's still no seventh flash.
To fake out the MPU board, use an alligator jumper wire and connect the top of resistor R23
(leg closest to U12) and the top of resistor R17 (leg closest to TP3).
This makes the MPU think the 43 volts is present, and
will allow the board to fully boot (7 flashes).
This happens because the 43 volts is reduced to 5 volts and then converted into an
"impulses train". This signal comes from pin U10 pin 18 and then the MPU
monitors this impulse train signal. If the signal is present the MPU thinks
the 43 volts must be Ok. By making the connection between the tops of R17 and R23
we simulate the presence of the 43 volt impulses train.
Problems After the 7th flash (game sitll doesn't work).
In a normal boot-up sequence, after the seventh LED flash,
the LED glows very dim (some LEDs show this more than others).
Occassionally, a game will do the seven flashes, but won't
go into "attract" (game over) mode.
Stern MPU-200 boards in particular can have problems where the
seventh flash is seen, but the game does not work.
Of course the first thing to check (especially on multiball
games) is if all the pinballs are installed and
the ball trough switches are working.
If there is a single dip switch on anywhere,
the MPU boots (seven flashes), then some score digits
on all displays come on for about five seconds, then all displays
go out (display blanking). Slam switch (and its capacitor) are
not the problem!
So what could be the problem? The answer is usually a bad 5101
RAM chip. Especially on Stern MPU boards, the 5101 RAM chip(s)
need to be the proper speed (100ns, unlike Bally which can use
a 300ns 5101 RAM chip), or the game will not work (even
though it passed the 5101 self-test at power-on).
MPU Boots Fine, but after Turning Off and Immediately back On, The MPU board
is Locked.
Game is turned on and works fine. Then the game is
turned off, and within a few minutes, turned back on. But the MPU board's LED is
locked on, and will not (flicker) boot. The reset section of the MPU board has
been rebuilt, as described in this document.
The first thing to suspect is MPU battery corrosion in the reset circuit.
Inspect the board for any damage due to corrosion. The problem may be
the reset line stays high from the battery power. When the battery is
discharged enough, the game will restart. This can happen from the two
8.2k resistors (R1, R3) at the bottom of the MPU board. Other resistors
in the reset section should be checked too (R2, R112, R120, R140, R139, R138, R140, R12, R11).
Seven Flashes Constantly Repeats.
The MPU boots and gets to the 7th flash, then start all over
and repeats the seven flashes, then starts all over and does it over and over
(like the game is constantly trying to reboot itself over and over).
This can happen from a bad 6810 RAM at U7, or possibly a bad socket or broken trace at U7.
Also there can be a broken trace or bad socket at the U11 PIA especially around pins 35 to 40.
Since U7 and U11 are in the "battery corrosion zone",
look for broken/corroded traces or bad chip sockets in this area.
But besides that,
if all -32 MPU board DIP switch
are off, the game goes in self-test mode (toggling alternatively every
solenoid, flashing controlled lamps and testing single digit at a time
on every display) after the seventh flash.
3c. When things don't work: Test EPROM & Fixing a Dead MPU board.
Leon from Europe wrote a test EPROM that is very handy for fixing a Dead MPU board.
"Why do I need a Test EPROM when Bally/Stern has this neat built-in system
of flash codes?" Well in most situations you will not need the Leon Test EPROM. But
in many situations it does come in handy. If the LED is locked on, this Test EPROM can
be very helpul. The best thing about Leon's Bally/Stern Test EPROM
is it requires a minumum of working MPU parts to run:
- +5 and +12 volts.
- Valid Clock signal chips U15 and U16 (usually not socketed).
- Test EPROM in U6 (either 2716 or 2732).
- 6800 CPU chip in U9.
That's about all that is needed (all other socketed chips can be removed to
minimize problems, and can be added one at a time after the board is running
the Test EPROM to confirm their validity, or all the chips can be left
installed if desired). The reset
section of the board doesn't even need to work - instead we can do a "manual reset" by
jumping TP5 (+5 volts) to CPU U9 pin 40 to get a the processor running.
The Test EPROM only needs the 6800 CPU at U9 and the reset/clock circuits.
It is not dependent on memory chips U7 (6810) and U8 (5101),
and the game-specific EPROMs (U1, U2, U5, U6). And the PIA chips at U10 and U11
don't need to be installed (even though the Test EPROM will try and test
these two PIAs).
The Test EPROM has a short program which runs from EPROM U6 and controls the two
PIA chips at U10 and U11. Basically it sets the U10/U11 PIA chip outputs
PA0-PA7 and PB0-PB7 and CA2/CB2 high and low, over and over at one second intervals.
While it does this it flashes the built-in MPU LED at one second intervals and
a Test LED which we will connected to CPU U9 pin 15.
This gives us the opportunity to test the PIA outputs using a Test LED or logic probe
or even a DMM. The Test EPROM does not care if the chips are
working or not, and it does not care about the other memory chips on the board either.
It will try and run this test over and over regardless, unlike the built-in Bally/Stern
test which will stops as soon as it finds a problem. This allows us to get the MPU
board working with a mimimum of chips (and a minimum of problems).
Remember it is always easier to tackle a small set of problems, instead of trying to
find all problems at once. If a MPU board can run Leon's Test EPROM, you are well
on your way to fixing the MPU board. It is always the initial step of making a
MPU board boot on its own that is most difficult. Problems past this tend to be
easier to tackle.
Download the Test EPROM files here and burn them into a 2716 EPROM:
2716 format Test EPROM.
Using the Test EPROM.
If using the Test EPROM "on the bench" outside of the pinball machine,
connect +5 and +12 volt (43 volt is not needed) as shown in the
Making a MPU Test Fixture section of this document.
This involves using a computer power supply and connecting +5 volts to TP5,
+12 volts to TP2, and ground to TP4. I highly recommend this approach.
If using the Test EPROM in the game, remove connector J4 on the
Solenoid Driver board to kill power to the solenoids.
With the power off, remove MPU board chips U1, U2, U5, and U6 (the game ROMs),
also U7 (6810) and U8 (5101). Note all these chips do not have to be
removed, but it's a good idea to minimum potential problems by
removing them. Also remove the two 6821 PIA chips at U10 and U11 (again not
necessary, but a good idea).
Because the Test EPROM is a 2716 EPROM, the MPU board need to be jumpered
for 2716 or 2732 EPROMs. Or if you have a MPU board with its original black 9316
ROM chips, the easiest thing to do is to make an adapter as shown in the
9316/2716 Adaptor section of this document
(note only one of the two sockets is needed, and the test clip does *not* need
to be connected - see the description below).
Instead of making MPU board jumper changes (which
could be mistakenly done wrong, making the MPU board more difficult to fix),
using a 9316/2716 adaptor socket is a much better idea. If the MPU board is jumpered
for 2732 EPROMs that is fine - this 2716 Test EPROM will plug right in without
any jumper changes and work.
The 9316/2716 adaptor for this application
takes two good quality (machine pin) 24 pin sockets, and sandwiches
them together. There are a couple pins that need to be cut and jumper wires added:
- On one 24 pin sockets, jump pins 21 and 24 together with some wire.
- On the above modified socket, cut pins 18 and 21 short so they won't plug into
anything.
- Plug the modified sockets into an unmodified socket. Make
sure pins 18 and 21 do not contact the unmodified sockets. To be double
sure this happens, you can cut pins 18 and 21 off the bottom socket too.
- Plug the 2716 Test EPROM for U6 into the modified socket sandwich.
- Plug the socket sandwich and EPROM into the MPU board at positions U6.
The Test LED.
In addition to the built-in LED on the MPU board, we also need to make a
"Test LED". Even though the on-board MPU board LED is present, without PIA U11
the on-board LED will not work. So to test a MPU board with a minimum of chips,
a "Test LED" is needed to indicate if the Test EPROM is running (without the Test LED,
there is no easy way to tell).
The Test LED will be connected to address line 6
of the 6800 CPU chip (U9 pin 15 or MPU connector J5 pin 16).
Take a LED and a 150 ohm resistor connected to the "flat side" of the LED leg.
The resistor side of the LED is connected to ground (TP4), and the non-resistor
side of the LED is connected to U9 pin 15 or J5 pin 16.
Use micro-clips to attach the Test LED.
Using the Test EPROM.
To get started, install the Test EPROM in the MPU board at socket U6. If
the board originally used black 9316 ROMs, an adaptor will be needed for
the 2716 EPROM (do *not* change the jumpers on the board!) Remove all
socketed components from the board except for the U9 6800 CPU, the U6 Test EPROM,
and U15 and U16 (which are normally not socketed anyway).
Do not have U10 and U11 (the 6821 PIAs) installed at this time.
Also do not have the U7 (6810) and U8 (5101) RAMs installed.
Power up the MPU board (ideally on the work bench using a computer
power supply for +5 volts to TP5, +12 volts to TP2, and ground to TP4.
The Test LED will immediately start flashing about once a second.
If the Test LED flashes in rhythm then the reset section of the MPU
board and the Clock circuit are working (a very good sign). Note the
on-board MPU mounted LED will be locked on if PIA U11 is missing or bad.
If the Test LED is not flashing: Probably the reset section of the MPU board
is dead or the MPU board is not jumpered correctly for the U6 EPROM installed.
To check the U9 reset,
with the board power on, use a DMM and check for +5 volts
at U9 pin 40 (this is the reset pin of the 6800 CPU chip).
If less than 2 volts, the reset is being held low, and
the reset circuit of the MPU board is not working (the reset circuit should
hold U9 pin 40 low for about 50 miliseconds, and then bring U9 pin 40 high to
5 volts and keep it high - this will start the CPU chip).
If U9 pin 40 shows 5 volts, then the reset section is working.
If U9 pin 40 is low and you want to simulate the reset circuit with a "manual reset",
power the board on. Then use a jumper wire and jump TP5 (+5 volts) to CPU U9 pin 40.
This will make the CPU chip's reset line "high", and it should start
the CPU running (assuming the CPU chip itself is good, as are all the
address and data lines to the U6 ROM).
If a "manual reset" does not wake up the CPU, try another 6800 chip at U9.
Still no LED flashing? Checking the signals of the U9 CPU chip:
- Check for a clock signal at U9 pin 3. A DMM will show about 2.4 volts, or
use a logic probe or an oscope for a clock signal. No clock, then
check U15 and U16.
- Check for the second clock signal at U9 pin 37. This should also show about 2.4 volts.
- Check U9 pin 2 for +5 volts.
- Check U9 pin 4 for +5 volts.
- Check U9 pin 5 for around 2.8 volts.
- Check U9 pin 34 for a positive signal with very short negatives spikes
(use a logic probe for this).
- Check the address line signals U9 pin 9 to pin 24 using a logic
probe, except A8,A9,A10 and A13 (U9 pins 17,18,19,23), as
these four address lines will be 0 volts.
If any of these signals are bad (and the U9 6800 was replaced with a known
good one), trace the bad signal to its source and repair it using the schematics.
A last possibility is that the ROM selection of U6 doesn't work.
Check the following pins of U6:
- U6 pin 18 without an adapter 2.5 volts (with an adapter 0 volts).
- U6 pin 21 is 3.6 volts (if no 9316/2716 adaptor) or +5 volts (with a 9316/2716 adaptor).
- U6 pin 20 is ground with very short positives spikes,
only seen with a logic probe or scope.
If all these signals are good, there should be a flashing Test LED (again, with
PIA chip U11 removed, the on-board MPU LED will be locked on). Once the LED is
flashing, replace the PIA chips U10 and U11. With U11 installed, the on-board MPU
board mounted LED should flash in rhythm (but opposite) with the Test LED.
Testing the PIAs Using the Test LED.
Using the Test LED, all outputs of PIA chips at U10 and U11 can be tested.
The Test LED will need to be connected as shown above, which is slightly different
than the U9 Test LED connection. The non-resistor leg of the Test LED goes to +5 volts
(TP5), and the resistor leg of the LED is used to probe the pins of the U10/U11 PIA chips.
Note with PIA U11 installed, the MPU board mounted LED will not blink too (but this
LED really does not help with testing).
Using the Test LED, probe the two PIAs U10 and U11:
- PIA Pins 2-17 high then low (Test LED on and off), alternating every second.
- PIA Pins 19,39 high then low (Test LED on and off), alternating every second.
- PIA Pins 26 to 33 are the data lines, and should be pulsing (use a logic probe for these pins).
If one PIA output does not flash, temporarily connect it (short it)
with the output pin next to it.
This will cause one of two things - Both outputs "dance": this means
the first output is dead and the 6821 must be replaced.
If both outputs do not "dance":
there is an short somewhere on the suspect output line.
If this is the case, disconnect the output line by bending the PIA pin up and out
of the socket, and connect the Tester LED to the extracted pin. If the LED dances,
the 6821 PIA is OK and the short is somewhere on the MPU board. If the extracted PIA
pin does not "dance", then the 6821 is dead and must be replaced.
Finishing Up.
If all the PIA ouput signals are there, replace all the other chips
(except the original ROM chip U6). The replaced chips should
have no influence on the test (repeat the testing of the U10 and U11 PIAs
using the Tester LED). If something is different there is something wrong with the
selection of the newly installed chips since it disturbs the test EPROM program.
Memory Test using the Test EPROM.
To execute this additional memory test, have all the MPU board chips installed
and the Test EPROM installed at U6. Also have the Test LED connected to
U9 pin 15 or J5 pin 16, as done before the PIA tests.
Power the MPU board up. Now press the red button
which is on top of the MPU board. The memory test will then start
and give you one flashes on the Test LED, and then a continual flashing
of the Test LED as the Test EPROM goes back to testing the PIA chips.
Note there are some restrictions to the Memory test.
Although Bally and Stern cpu boards can be interchanged, there is a major difference
between the -17/-35 Bally MPU board and the Stern M-200 MPU board.
The Stern M-200 has an extra 5101 memory chip extra at U13.
To make both types of boards use the same memory test, Leon used some tricks in
programming the test EPROM.
If this wasn't done, and you're testing a Stern board without U13 (or with a bad
U13 chip), it would be reported as OK, because a regular Bally board
doesn't contain a U13 chip.
When the Test EPROM is started, the Test LED will start to light in rhythm, and
this is the regular PIA test. Now push the MPU board mounted red button.
The Test LED will turn off and
after one second it should flash a first time.
This means the test of U7 6810 has succeeded.
Again a second later the Test LED should start flashing continually (indicating
a good "second flash"). The test has run on U8 (5101) and U13
(5101) and has succeeded. But if the LED flashes this second time 5 seconds
after the first flash, this means the test has succeeded but *only* for U8.
So on a Bally board both flashes have to be about 5 seconds apart, meaning both U7 (6810)
and U8 (5101) are good. On a Stern M200
board the second flash (continual flashing)
has to be just one second after the first flash, meaning
U7 (6810) and U8 (5101) and U13 (5101) are all good.
But if the second flash comes 5 seconds later, then the M200's U8 is fine but U13 is bad
(you can test this by removing U13, or swapping U8 and U13).
So when testing, if U7 or U8 is defective there'll be no flash, or only one flash.
If you have a Stern M200 board and two flashes (continual flashes)
are seen with 5 seconds between them,
then U13 is not installed or U13 is bad.
This way one test EPROM can be used for either a Stern M-200 or a Bally -17/-35 MPU board.
Another restriction of this memory test (not the PIA test)
is that it cannot use a 9316/2716 adaptor socket.
When using the adaptor socket it's not possible to use U7 6810
(check the repair manual for Bally Stern MPU
boards). Because if only two flashes are seen with the game ROMs installed,
there's is a problem with memory chips. But unfortunately the Bally test does not
say which memory chip (U7 or U8). So if you don't want to adapt your MPU
board to use EPROMs, you cannot use the Leon Test EPROM for the memory test
(but the PIA test works fine).
All Done.
Now that all checks out,
install the original U6 ROM, and count how many times the MPU board's LED
flashes (should be 6 or 7 times). If less than this, see the
LED flash count section of this document.
3d. When things don't work: Game ROMs, EPROMs, and
Jumpers - the Basics
Bally started using the improved -35 MPU board from 1979 to 1985.
The later -35 MPU board can be used
for ANY game from 1977 to 1985. The difference between the new -35 MPU
and the early -17 MPU is mostly how the game ROMs are used and addressed (though
the manufacturing and the type of sockets in the earlier -17 boards
is also considered inferior to the -35 MPU boards). This section will
address general concepts that are used on both the -17 and -35 (and -133)
MPU boards.
Bally has provided us with about 35 different
"jumper" locations on the -35 (and -133) MPU board, and about ten on the -17 MPU.
This was done to handle
all the different game ROM (read only memory) chip configuations,
for all the different games. Depending on supply and demand for certain
ROM chips, Bally pretty much had all the bases covered. They could
use any combination of ROM types and sizes to fit their needs.
Important: Before you Change any Jumpers!!
It is EXTREMELY important that you have a working MPU board
before you change any jumper locations! If you MPU board
currently has ROMs in it, get it working first before you play
with the jumpers. If you have your MPU board jumpered incorrectly
for the game ROMs installed, the diagnostic LED light will stay
on and the board will not power-up. So it is absolutely important
that the jumpers are correct for the ROMs installed. Get your
MPU board working first before proceeding.
Which MPU board Is It: -17 or -35 or -133? (How to Tell!)
Of course Bally silkscreen the MPU part number (AS-2518-17 or
AS-2518-35 or AS-2518-133) right on the MPU board. But sometimes
due to battery corrosion, etc, the part number can not be read.
It is important to know which board is being worked on, as the
game ROM/EPROM jumpers are different.
Basically there are two flavors of MPU board: the -17 or -35 (the
-133 is really a -35 board with R113 changed to a diode CR52). The easiest
way to tell which board is to examine connector J5. On a -17 MPU
board, this connector will have 32 pins (including the removed "key" pin). On a -35/-133
MPU board, J5 will have 33 pins (including the removed "key" pin).
Bally/Williams' Jumper Information.
Though I personally don't recommend or use it, here is a link to the information
that (recently) Williams posted about the original Bally board jumpers.
You may find this information helpful (though personally I don't). It lives at
ballyrm1.htm.
Masked ROMs versus EPROMs.
If you are repairing a game, you may be replacing the original masked
(black) ROMs. These ROMs, as they get old, break very easily. In particular
their pins tarnish and/or break off. The black tarnish is silver oxide,
which is caused by oxygen and moisture in the air, and dis-similar
metal electrolytic action between the silver plated pins and the tin
plated sockets. The black oxide doesn't conduct well, and this can
make the ROMs stop working correctly. They are not available any more,
but they can be replaced with EPROMs.
EPROMs are basically the same as masked ROMs, but have
a small cyrstal window on top of the chip. If UV (ultra-violet)
light is shined through this window, the chip can be erased
and re-programmed. An EPROM programmer is necessary to re-program an EPROM.
These attach to your computer (though there are some stand alone
ones too), and can "burn" a blank EPROM with a game's program code.
After the EPROMs are burned, a sticker is placed over their
window to prevent light from erasing them. EPROMs are the best
replacement for your old and tired black masked ROMs.
Chances are if you are doing any repairs to a Bally MPU board,
and you need new game ROMs, you will be installing EPROMs.
EPROMs are available blank from many sources. But you need
to have them "burned" first before you can use them.
The two chips on the left are the black "masked" ROMs.
All masked ROMs used in these Bally games are known as "9316"
EPROMs can be 2516, 2716, 2732, or 2532. The last two numbers
identifies the size of the ROM (16k or 32k bits of program data).
Masked ROMs are only usable in the game they were designed
for. Note how their legs are tarnished black. The two chips
on the right are EPROMs. Note the "window" which allows
them to be erased, and re-programmed. Also note how the
EPROM's legs are not tarnished. You can just read the
notation on the one EPROM as "2532".
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The Program Code that Lives inside the ROMs.
The memory inside each ROM or EPROM is the heart of your
game. It contains the power-on diagnostics, the switch
matrix, the game rules, and the coil assignments, among
other things. Each model of pinball game has different program code
that must be installed only in the game it is designed for.
The program code is stored (burned) in your game's ROMs or EPROMs.
The Jumpers.
Each kind and size of ROM chip has its own set of enable and address
requirements. To allow a board to use any type or size ROM that
Bally had in stock, jumpers were used on the MPU board.
It also provides a way to take a MPU board out of a
newer game, and put it in an older game (and only have to
change the jumpers and the game ROMs).
The wide array of jumpers Bally provides is very confusing.
Some games use just one ROM at U6. Others use three ROMs at
U6, U2, and U1. The size and type of these individual
chips can change too.
What Type and Size are My ROM chips?
Before you can change a MPU board's jumpers to another game
(or for new EPROMs), you need to know the type and size of
chips you are installing. If you are installed Masked ROMs,
these are all 9316 (16k bits of data) or 9332 (32k bits of data).
If you are installing
EPROMs, you need to read the markings on the EPROM. They will
say what type and size of EPROM you have. They will be 2516,
2716 (both 2516 and 2716 are the same type of 16k bit EPROM),
2532, or 2732 (32k bit EPROMs). Note the jumpers for 2532 and 2732 EPROMs are
different, as these chips have different pin assignment (but the
jumpers for 2532 EPROMs and 9332 ROMs are the same, which is the
ONLY sharing of masked ROM and EPROM jumpers). This
is unlike 2516 EPROMs and 2716 EPROMs, which are identical and have
identical jumpers.
Texas Instruments TMS2716 Warning.
Do *not* attempt to use TMS2716 EPROMs in any Bally/Stern MPU or sound board.
The TMS2716 EPROM requires -5, +5 and 12 volts to operate and
are not pin compatible with "normal" 2716 EPROMs. Also most EPROM
programmers can not program a TMS2716. Note that TMS2516
*are* compatible with standard 2716 EPROMs and work fine.
What if I don't have an EPROM Programmer?
You can also buy the above EPROM chips already programmed
in 2732 format (or any other size) from
a variety of sources for a nominal fee.
Using 2532 EPROMs instead of 9332 Masked ROMs.
If the game in question is a later Bally game with 9332 masked
ROMs, these can be changed to 2532 EPROMs with NO jumper modifications!
This can be handy and convenient if the original black 9332 masked
ROMs need changing, but the repair person doesn't want to mess
with the jumpers.
What Do the Masked ROMs Chip Numbers Mean?
If the game in question uses original black masked ROMs,
there are numbers on the ROMs that denote information about
the chip. This information is can be seen by clicking
ballyro2.htm, where
the ROM numbers are sort numerically. Another page located at
ballyrom.htm shows the
same information, but sorted by game name.
Also shown are the original jumper settings. In addition,
the chart at roms.htm shows the Bally
ROM part numbers and checksums.
Note the higher -xx number means a later revision. In the case
of the U6 chips, that revision is important, as generally
a game can not be run with the "wrong" U6 part. But for the U1/U2 chips, it
usually means a later version of the same game (and all the
chips must be of the "correct" revision to match the others, though
there's not always a good way to know what that is).
As an example, Lost World uses "720-28" for U6. But then the other
chips should all be "729-xx", with the latest revision
being "729-33" at U1, and "729-48" at U2. If the game has an earlier
version, they would have some other numbers after "729-". But note
there can be no mixing of old and new versions!
Do I have the Right Jumpers/ROMs Installed?
As stated above, if the jumpers are set incorrectly for the ROMs
installed in the MPU board, the MPU LED will be locked-on. This happens
because the ROM code is what turns the LED off - if the MPU can't access
and run the ROM code, then the LED will never turn off and start its flash
sequence.
On the CPU chip U9 pin 5 is the VMA line (valid memory address), and
it should never be stuck HI or LOW (it "polls" the U6 ROM).
A bad U6 ROM can affect the CPU U9 pin 5's behavior.
The CPU's U9 Pin 5 behavior is controlled by U9, but tying it to a bad
or mis-jumpered U6 ROM can cause many problems.
So if you are confused about the ROM jumpers, try this:
Boot the MPU board with only U9 and U11 installed (all other
socketed chips removed). The LED will stay on, but using a logic probe check U9 pin 5.
It should be pulsing. Power down, add ROM U6 and repeat. If U9 pin 5 is now stuck high
or low, U6 is either bad, or you have the wrong jumpers.
Game ROM Software.
If you have an EPROM programmer, the game ROM software is needed for
programming into EPROM(s). The best solution is to upgrade your
current -17 or -35 MPU board to use 2732 EPROMs. But since the first
eight Bally games from 1977 to 1978 use a -17 MPU board (which is
fairly easy to convert to two 2716 EPROMs), a ZIP file just for those
games is 2716 format is provided (bly2716.zip). Note starting with
the first -35 game (Lost World) Bally used three 9316 ROMs, which
are better utilizied in two 2732 EPROM format.
- All 1977-1985 Bally software in 2732 format:
Bly2732.zip.
- All 1977-1978 Bally software for -17 MPU board in 2716 format:
Bly2716.zip.
- All Stern EPROM software:
sternROM.zip.
- Bally Pacman MPU and Vidiot board software:
babypac.zip.
* Go to the Bally Repair Guide Part 1
* Go to the Bally Repair Guide Part 3
* Go to the Pin Fix-It Index
* Go to Marvin's Marvelous
Mechanical Museum at http://marvin3m.com
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