I just finished rebuilding a Bally MPU. I thought I'd give it another test before I put it the parts drawer. I connected my power supply and got a solid on LED. I turned it off then on again and it booted fine. Tried it again a few times and it booted every time. Then I tried a Stern MPU and it booted first time. I went back to the Bally and it got solid on , on the first try then booted. It does this every time I let it set for a few minutes. I got 5.2 V and 13 V with solid on and when booted. I then tried my old power supply and got the same results. The only game I have available at this time is a working Meteor (MPU 200). So I connected only the J4 to test in the game. Same results - solid on the fist try. Turn it off the back on and it boots.
I've tried two power supplies and in a game. It just won't boot the first time.
This is going to be a tough one. Any suggestions where to look?