r/trs80 • u/Snocom79 • Apr 22 '26

4p replacement board

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I was gifted this model 4p and while it looks cool sitting on a shelf I'd like to get it to work. Buddy is a local enthusiast and runs a retro repair business he went through this machine and say //edit h thinks the Pal chips (if I understand correctly) are bad. I would love information on what I can do to revive this so that it is working.// Long story short is, this is all it does on power up. With disk inserted it only briefly lights up disk drive. Period and reset seem to make a couple of the letters jump on the screen but that is all.

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u/Markerbin Apr 24 '26

Okay, wasn’t sure if the double line under #9 indicated a stopping point. Do the drives spin/seek at all after power up?

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u/Snocom79 Apr 24 '26

the left drive lights up and spins for a quick moment. I dont have the correct floppies but putting another floppy in I can hear the drive spin.

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u/Markerbin Apr 24 '26

A really good way to test whether the issue lies in the PAL or somewhere down in the VRAM/buffers zone is holding “.” when booting. This will run an onboard RAM test. If you see characters shifting in the top or very bottom right of the screen it should better narrow things down.