All 6 special solenoids lock on at power up? Or is it just 2 and then the fuse burns?

All 6 solenoids go through U-49. U-49 is next to the damage area. It may have been damaged to. In attract mode use logic probe and take some readings.

Red lead to 5 volt test point on CPU. Black lead on ground test point on CPU. Set TTL/CMOS to TTL. Probe each lead of U -49 and report back.

So the U-49 chip is passing the signals through correctly, but the signals going into U-49 are wrong. The six input signals come from 3 different pia chips. Pins 1,3,5,9,11 and 13 all need to be low.

Start with the first Pia chip U-54. U-49 pin 1 and 13 go to Pia U-54 pin 19 and 39. If the Pia chip is good, then there is a broken trace from U-54 pin 39 to SR-19 pin 2. Also since you got a nothing signal ( 0.8 volts-2 volts) on pin 1 of U-49, the trace from U-54 to SR-19 pin 10 is not completely broken but has high resistance which needs to be zero resistance. Now if you find the traces to be fine then the PIA chip maybe bad, but I doubt that all 3 PIA have the same outputs bad. Use this as an example for all 6 inputs of U-49.

u-49 (resized).PNG

The first pic shows that the signal goes to 4D1.
4D1 is page 4 of 4. Up and down is D. Left and right is 1.
So look for the signal in the upper right corner of page 4. Pic #2.
U-41 pins 19 and 39.

pb (resized).PNG

pb1 (resized).PNG

This is the only output that is correct, now you need to figure out if the other 5 outputs are bad pia chips or most likely bad traces due to acid damage. Could also be a bad solder job on the socket.

Very unlikely.

Do this.

Easy to test for continuity between the pia chip and the resistor pack to know for sure.

Well this will fix SS#5 the right kicker.

I would replace ZR-8 and test the resistor pack, then add a jumper.
If the trace was laying across sr-20 pins, this could have locked on all 6 SS coils. Now that its off retest the board to see if all six still lock on, maybe the pias are fine.

The displays and sound will not work. But you need to replace zr-8 and the jumper before testing or cut the wire from SS #5 coil to keep it from locking on.

You can cut the zener off to test, but you need the jumper for sure.

Wouldn't hurt.

This is a step in the right direction.

Test the rest of the ZRs with and ohm meter. Good reading is @5k ohms. When the trace shorted the resistor pack it may have caused damage to the rest of the ZRs.

Lift one lead off the board and retest the ZR to see if it is the ZR or is it somewhere else on the board.

If this is on the bench, then you need to lift a leg of C-75, ZR-8, pin-2 U-49 or pin 2 U-50 until the ground short goes away.

If the board is a 11a then pin 6 NC pin 7 NC. If its an 11A board then 6 and 7 to ground.

Correct, I don't know why I didn't look back at the pics.

You don't need to connect j-19 just to see if it's fixed. Just use your ohm meter or logic probe. Locking on the coils each time will kill the diodes and driver's.

With J-18 and J-19 off the board, power on the game. After the Cpu boots, first check switch inputs J-18 with the voltmeter, pins 2,3,4,5,8,9 should have 5 volts while in attract mode. Any pin that is lower then 2 volts will trigger U-45 and U-50 and turn on a driver transistor when you start a game. Once the switch inputs are good you check the driver outputs on J-19. Pins 3,4,6,7,8,9 resistance should read O/L in attract mode to ground. Then start a game and retest J-19, all should read the same as before until you trigger a switch input during a game or run coil test. Now before you connect J-19 again you need to replace all SS coil diodes.

pb cpu (resized).PNG

Correct.

This will lock on the coil when you start a game. Is the connector J-18 on or off the CPU?

Anything is possible with the number of times the coil were locked. Are U-45 and U-50 in sockets? If yes, pull both chips and then test J-18 pins, all should be 5 volts.

Your making good progress, try a new U-49 and retest. The end is in sight.

So do I, but more benefits then downfalls.

With U-49 removed, what do you read on U-49 pin 1?

The needs to be @ 5 volts, check the traces and solder joints of both chip sockets and the resistor pack.

U-49 pin 1 should always be 5 volts unless in coil test on this particular special solenoid. Then it would be a high with low pulses. Since you are reading 1.39 volts I would guess that if you measure at the resistor pack it maybe 5 volts. But a poor solder joint on the pia or U-40 chip socket maybe causing the voltage to drop under load. Your real close to finding the problem here so stay after it.

Not to many items to check here. How are the traces?

pia (resized).PNG

Do you have five volts at SR-19?

pia (resized).PNG

What does pin 1 of U-49 read if you remove U-54?

I think so.

I would put the board in the game and reconnect every connector but 1J-19.
I would then turn on the power and the check resistance from ground to each of the 6 SS TIPs metal tabs. Should be high resistance. If OK, then I would start a game and retest the 6 SS TIPs. If OK then I would replace the 5 coil diodes and check the coil resistance. Then I would reconnect 1J-19 and do a coil test to see if every thing is all good.

PLAYBALL!

Since you have some of the PIAs in sockets now, are you going to test the counterfeit PAIs one at a time to see if they are working chips?

But disconnect J-11,J-12 and J-19 so a coil wont lock on.

Your the only one who understands my weird sense of humor.

Yep.

Your questions were always on point to me.

Then don't, I was just curious as to whether they were part of the cause or not. Now it sounds like it was a factory U-54 and a couple of other things that cause your headaches.

Enjoy your success.