I have a Gottlieb System 3 machine that needs lots of work. Somehow the adjustment pot on the 5volt regulator was missing so the full 12 volts was applied to the 5v rail. Needless to say the board set does not boot. I am going through each board on the bench to get them working, starting with the mpu. What I am looking for is some in depth theory of operation for the mpu. I have read just about everything I can find on the web about these and nothing really explains how it all works, just some tips on common failures and chip swaps. The main issue is that all the chips except the game eprom and ram are soldered in (with every ic leg bent over I might add). I really don't want to have to unsolder and replace every chip if I don't have to.
I do have a Super Mario Bros. Mushroom World game that is working. I repaired this one months ago so I do have something to compare with. My first task is to get the mpu to run on the bench.
The battery was missing altogether on the board so I installed a battery holder and battery. I then found that the DS1210 was bad. I had 3.15 volts from the battery and 5 volts from the supply but it was still not passing 5 volts to the memory. I replaces the DS1210 and that now works. I am still not getting the LED to flash like it should if everything is running, which my good board from SMBMW does. I have replaced the 74HCT123AN which did not help. I also have a jumper on the disable reset line so I do not get constant reset on pin 40 of the cpu.
So, I am looking for some detailed information on the theory of operation on how the circuits is supposed to work. I have an electronics background and the all the tools needed to troubleshoot computers, which I have done for 40 years, so the more detailed the better.
Thanks in advance for any information anyone can provide. If there is nothing out there like what I am asking for I would be happy to provide any learning I might make if folks think it would be helpful.