[Coco] seeking for help...

[Camillus Blockx]

Thanks will do...🤔🤔

On Tue, Feb 12, 2019, 4:24 PM Gene Heskett <gheskett at shentel.net wrote:

> On Tuesday 12 February 2019 13:21:26 Camillus wrote:
>
> > Hi, coco users,
> > Anyone can give some hints on how to repair a coco2 that has bad sync,
> > did all the classic chip swapping to no avail. Scope images are close
> > to what I found in coco2 service manual, but the device I have is a
> > Korean made, so no correct schematics. The coco powers up with a
> > scrambled screen, I can see the square and some color stripes on the
> > right side. Sometimes it comes up ok, even with BASIC logo, but after
> > switching some ram and other Ic's the Basic does not show. Don't know
> > I made things worse. Anyway got lost a bit so maybe some hints? Thanks
> > in advance
>
> Two candidates. That big filter cap (look at the 5 volt line with a scope
> looking for dips below 5 volts at 2x the line frequency) and bad memory,
> again best checked with a scope, look for one chip with a different
> waveform at its data i/o pin, its probably bad if markedly different
> compared to the same pin on the others.
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
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> -Ed Howdershelt (Author)
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>
>
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