Been struggling with this one for awhile and running out of ideas.
Recently picked up a Big Game, had some issues, battery damaged CPU, etc. I got it working with an Alltek MPU board. At first, it would work/play fine until it warmed up, then the "wrong coils firing" behavior described below would kick in. If you let it cool down again, would work for a short while until it warmed up again.
When starting a game the top right drop target bank will continuously reset (about once a second). Sometimes, if there are no drop targets down when the game is started, it will be fine until one is hit, then continuously resets.
In solenoid test mode, only the following coils will fire at all, in this sequence:
Left Pop Bumper: 1, 2
Top Right Drop Target: 4, 8
Left Sling: 5, 6
Saucer 13, 14
With the ball removed, switch test shows "0", so no stuck switches that I can see.
In the past I've seen these type of temp. related issues and resolved with either reflowing solder joints or replacing sockets. So, I reflowed the solder on the connector pins and IC pins on the SDB. After that, it never works, even when cold, always fires the wrong coils. So at least it's consistent now.
So I'm thinking, it MUST be the SDB then, perhaps U2 was starting to fail and my reflow pushed it over the edge. So I swapped out the SDB with a working one and... the problem persists. Not the SDB after all.
I then re-pinned the female connectors for the J3, J4, and J5 connectors to the SDB. No difference.
Next stop would probably be to re-pin the MPU connectors, but I'm running low on the small pins. If was to try re-pinning an MPU connector, which one should I start with?
Any other ideas? With known good MPU and SDB boards the problem has to be elsewhere, right?