Helping a friend with a Star Trek. It is having the following symptoms:
1. Dmd display showing dots, not words. Sometimes the dots change, picture below.
2. There was no noise.

After some period of time 15 minutes or so, it started up, but seems to keep restarting.
I’m guessing some issue with main cpu board, but not sure where to start.

Batteries on motherboard were good (I removed them).

Suggestions on how to proceed?

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More info. I am able to hear proper sounds. I can get into the diagnostics of machine. None of the solenoid tests run, it looks like only the one test of all lamps runs along with the dmd display test.
I was able to cause a factory reset.
When in test mode, the machine will reset (computer).
When turning on, no solenoids reset.
In diagnostics mode, it says there is a ball missing, drop targets are down and a whole lot of other things. The drop targets don’t reset. Not sure on the ball status. I am thinking the issue isn’t with the dmd, but the Board driving it.

Any one have suggestions on which board(s) to check and how, or where to send for repair?

You are correct. There were issues with the power supply, needed new caps and some cold solder joints repaired.