So one of my two working Gameplan MPU-2 boards was having a couple issues and I finally tracked them down. Sometimes the board wouldn’t recall the saved settings and occasionally it wouldn’t boot. If I reseated the power cable it would come up. Re-pinned the power connector and would still see issues. This is a board that had a lot of poor prior work that I had to tear off and redo.
Isolated it where one it was running if I pushed on the PCB to flex it the board would reboot. Those are some of the worst to find as it’s intermittent. Went back over the area that I was flexing abd reflowed anything even remotely questionable. Then cleared out the solder in the in that area and resoldered using wire wrap wire in the via to ensure a solid connection. That helped and no longer would reboot when flexing the board up by the lamp connector but while better the board still wouldn’t boot every time. I could get it to boot and also reset by pressing around near the crystal. So more work. Did the same fix on the vias in that area as I’ve run into opens with those before. Also removed the crystal that had been reflowed by someone prior and noticed there was too much solder on each pin and one side was for sure making contact with the metal crystal body. Resoldered that with an appropriate amount of solder and added an insulator under the crystal as I’ve seen on some other boards to ensure no contact with the crystal case.
So far so good and the board has immediately booted every time and retains the settings. Both the boards are using and off board battery pack and have 1n5817 blocking diodes on the boards.
There was one pop bumper that was really really weak. Found that someone installed a Gameplan chime coil there instead. Bought the correct coil and now that works perfect too.
While going through it found a couple broken coil stops. I found that the classic Stern (copper colored) fits perfect and is a lot more robust. I just ordered extras so I’ll can replace the remaining broken one and keep spares on hand to replace the rest if needed later.
Have a couple switches to adjust, replace one large filter cap that had too much ripple, then a little more cleanup and these two games are done!
It is going to help having two working machines side by side as I continue work on my alternative MPU so I can compare updates side by side. Also just got in some 7 digit displays that I can use to ensure I can code for and support those for games like Sharpshooter II.