[Coco] CoCo 3 Display Problems

[Ed Snider]

Does kinda sound power related.

I'd probably replace the electrolytic caps and then see where it's at,
though you might try adjusting the trim capacitor on the GIME clock
circuit first to see if that has any effect.

- Ed



> On Sep 25, 2020, at 2:21 PM, Kurt Randall <kurtrandall at gmail.com> wrote:
> 
> Just wondering if anyone can help me with a problem I have with a CoCo 3 I
> recently picked up. I'm new to CoCo's -- my 8-bit computer experience is
> with ti99's, Apple IIs, and ZX Spectrums.
> 
> My problem is that the display in both RF and Composite is shaky, but the
> problem goes if I plug in my CoCo SDC. I have one game cartridge, and that
> seems to help too.
> 
> I tried re-seating all the socketed chips, cleaning connections, tried a
> couple different cables, and a couple different screens (LCD tv, CRT
> composite monitors, CRT tv). Without the SDC plugged in, the LCD tv always
> has problems with the top of the screen -- the top moves back and forth
> about 1/4 of the way across the screen, while the bottom is fine. The CRTs
> have shaky horizontal stripes -- it looks like every second line is a bit
> wiggly, but they are usable.
> 
> If I plug in the SDC the CRTs are fine, while the LCD is only fine unless I
> try running a game, then the problem comes back.
> 
> Anything I should be looking at? Capacitors perhaps?
> 
> Thanks!
> 
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