System 1 doesn't alarm like MPU4, instead the reels continue to spin (see video) System 1 doesn't have nice convenient pins for the logic probe either and I found it hard to get the probe leads on.
We checked the output phase of IC34 which are stuck high. Magik suggests removing IC34 and socketing it. I use a 4050B pulled from one of the other boards. Power up, wait... (the wait on ACE machines seems forever)... wait... it shows 74 in the LED, so far so good. Close back door switch, 06 is displayed, so far so good, reels spin and index. Machine goes into attract. It works. Board 2 is repaired. Board 4 is next, I think that could be the reset cicuit, but we'll see tonight.
ACE SYSTEM 1 Board 4 - Reset stuck - LED on the PCB stays on. After 5 minutes the machine will eventually reset.
I went through the reset circuit. Changed Tr8 and Tr9 - BC337
Replaced R17 and R18 (schematic is wrong) R17 is the 1K and R18 is the 220K. R18 was bad. Now it comes out of reset and the LED goes out. I put IC34 (borrowed for the first faulty board) back in out a the battery damaged board, so now it's indexing OK.
Just watching it for a bit just to make sure those slides don't mad again. (15 minutes in and its been calm)
Board 3 boots - I can't find the fault at the moment. There must be one???
Until I get a battery and live with it for a while I can't be sure what it is?