I'm working on a Solar Ride and am having some troubles with coils firing on boot.

The machine resets correctly however before showing the displays, both out kicker coils fire in sequence. They do not lock on, just one fires then right after, the second one fires.

The credits reads "72" and the ball-in-play reads "70".

Upon starting a game, one of the kickers fires every few seconds and scores the appropriate number of points. It continues to do this until I shut the machine down. All other switches do appear to register points as well if I hit them.

If I start a game without the driver board connected, the points are still scored over and over which points to the mpu.

To confirm that the mpu was the issue, I've installed a good working replacement and the game plays as expected, with no coil fire on boot.

If I remove the game PROM the coils no longer fire on boot but of course I can't play the game at that point.

Upon running the 13th diagnostic, everything appears to fire as expected however switches 30-35 and 40-44 are detected as closed.

Diagnostics 1, 3, 4, 5, 7, 8, 9, 10 all show garbled numbers. However all displays check out in diagnostics 11 and 12.

I have done all ground mods, bypassed the tilt, and replaced a bad inverter at Z9. I have also tested Z29, Z27, Z8, Z28, Z6, and Z7.

I have swapped out U4 from another board with the same results.

All pulses are correct on TC1.

If someone could perhaps point me toward a test point, that would be great.

Thanks!

Ah, right, thank you. I've now cleared all of the audit memory and now all zeroes show instead of garbled numbers, however the game is still behaving incorrectly as described above.

I actually only have one PROM which I transfer between boards. The PROM operates as expected in the known working board.

This is what I had suspected. I'm fairly certain my U5 is bad but I was hoping perhaps something else may be the problem. I could pull a good chip from one of my working boards although I'm not really willing to risk it with those not being in production anymore.

Yes, sorry, I have heavily utilized of http://www.pinrepair.com/sys1 in getting this far. The battery appears to be in good shape as the scores are restored at "000000" when restarting.

Thanks you guys for all of your help!