gottlieb system 3 , I"m stuck

maddog14

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Operation Thunder.
Board LED's are solid on and not blinking. I have 5 volts coming out of the power supply. The alphanumeric does not light up. The resistor board is overheating and is burnt.

Game turns on and does not boot up.

Yes all fuses were checked, along with all connectors. As a goof I replaced the U11 chip. No difference.

With game off, when I unplugged the cable between the driver board and cpu board, and turned game on, the main play field coils powered up

Yes, I looked through two on line system 3 guides. No immediate help there.

Where should I go next?
 
OK I tested the chip in the U4 position, which is the same as the U5 chip. Testing bad.

What is the function of the U4 chip?
 
Indeed, it is a 6522. I wonder out loud what it does for the pinball machine?
 
Thanks!!!

I bet you dollars to donuts that is why my machine is dead when I turn it on and wont boot up.

There are also I/Os going to the driver board and display controller board. Not that it's really relevant in the context of a bad VIA causing the MPU to not boot.

If there's a bad 6522, and the start-up test code detects it, the MPU won't boot. If you've tested the VIA and it's bad I would be more surprised if it DID boot. Wait... we ARE talking about Gottlieb here. I take that back.
 
The board now boots!!!!!

So, I determined that the 6116 memory was junk. when installed the ds1210 voltage output dropped 1 full volt. Installed the new 6264 memory. voltage perfect.

With board installed in the game with the P4 plugged it, sound board did not boot. unplugged, sound board did boot. Replaced and socketed in the 6522 at the U5 ( the U4 had already been socketed and replaced)

Still no boot from PC power supply. I started messing around with my logic probe on the U1 processor. All of a sudden, the damn led starts blinking. I'm thinking "Hot damn"

I power down the board and slap it into the machine.

I turn on the machine.....

Boom shockalacka I have a working game. (except for a hand full of solenoids) .

Yes I replaced the U5, but until I messed around with the logic probe on the U1 nothing.

Beats the hell out of me, but my game works enough now that I can fix the rest!!!!

Thanks a bunch guys for some of the feedback!!!!!
 
Some basic things to look at that are apparently problematic. If the pot on the power supply board is original, it can drift the voltage up or down and cause the game not to boot. Also, the battery on the CPU board can go dead-or just get week for that matter and cause the game not to boot. It may not be either of those, but I hear they cause a lot of problems. Were both causing problems on my Freddy.
 
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