TRS80 Model 4P CRT contrast fail

Chuck Guzis cclist at
Thu Nov 23 14:43:56 CST 2017

On 11/23/2017 11:34 AM, Adrian Graham via cctalk wrote:

> None of the pots on the video board deal with contrast so I’ve got it out on the bench to remove and test the capacitors. What else can I look at at the same time? Someone else has already mentioned the transistors Q101, Q102 and Q103 (on the yoke board).

Have you tried replacing C101?  What happens if you temporarily remove


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