Category Archives: Electronics

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Fixing a TRS-80 Model 100 LCD Issue

I recently pulled out some of my old computers to dust them off and check them out.  I have a sweet Tandy TRS-80 Model 100 that always worked fine, but I never really used it a whole lot.  So after typing some BASIC code into it and running it for a few minutes, I noticed the LCD was flickering off and on.  Eventually it stopped showing up altogether.

I figured this was probably the contrast control potentiometer needing a cleaning, but it was smooth as a whistle.  I did a bit of searching to help me narrow down the issues that could cause this… and didn’t turn up much.  So hopefully this post will help others that might have the same problem I did.

TL,DR; I had some dried up electrolytic capacitors (C49, C54) that needed replacing.  That’s it, a simple -5V (VEE) power supply issue.

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