I've got a Bally AS-2518-17 mpu I'm working on. When I got it, the LED would just come on and stay lit. The board had some battery corrosion so I removed a few components in the reset section that were in the corroded areas, fixed the battery corrosion, installed machine pin strips for the 5101 and installed new parts for the ones I removed in the corroded areas. I also replaced the .100 male header at J4.

After doing this, the LED does the quick flash, flashes twice and then sits there for a moment, and then repeats the two flashes, sits there for a moment, etc over and over. I swapped out the 5101 with a new one, traced back all it's pins which were good. I also installed machine pin strips for the 6810 and swapped in another 6810 but no change. I also replaced the 4011 at U19 but that didn't fix it. All the voltages are good as tested at the MPU board.

I'm a bit stumped. Never had one that would keep flashing like this. Usually it just stops at one of the flashes. It's like it's resetting after the second flash.

Any ideas?

Forgot to say that I tested the 6810 with my NeoLoch tester and it passed. I'll dig thru all the traces again and see if I can find anything

I figured it out. I had completely forgotten that I bought one of the 6821 PIA testers for my NeoLoch. I tested both of the PIA's and the one at U10 tested bad. Installed a working one and the board booted up just fine. Problem solved!