[Coco] Coco 3 with problems, can anyone help me troubleshoot?

gene heskett gheskett at wdtv.com
Sat Feb 11 10:08:46 EST 2012

On Saturday, February 11, 2012 09:39:31 AM haywire666 at aol.com did opine:

> I have a color computer 3 with some problems. I thought it was a cold
> solder joint or something. Occasionally it would not boot right (I'd
> get a garbage screen) The real problem however is that once its
> working, I can save programs with csave to cassette, but when I try
> cload, I get an S on the upper left corner of the screen and then it
> just hangs.
> Has anyone seen this before? Can anyone give me some trouble shooting
> tips? Not being able to save programs (just bought a cassette for that
> purpose) is driving me kind of nuts.

I have seen symptoms resembling that when the GIME chip needs cleaning, 
along with its socket, and reseated.

Do NOT try to pry it out of the socket as that will crack the socket, 
reducing its contact pressure on the chip forever.  What you need is a 
'cpld' puller, which has two hooks the fit in the corner slots and lifts 
the chip straight up.  The shack did sell them, and may yet.

This stuff can stand water, so use your fingers under running water to 
polish some of the oxide off the contacts on the edge of the chip, possibly 
aided by a bit of comet scrubber as long as its rinsed off VERY well, lay 
aside on a towel to dry.

Then take an old frayed toothbrush, wet it, scrub it on a bar of lava or 
use the comet again, and brush the socket gently and rinse until the 
contacts aren't nearly blackened with age but much lighter colored.

Rinse ALL that stuff away too. 

Another method, if you have a silver polish liquid called Tarnex, in a 
black plastic bottle at the grocery store, that will remove the oxides 
chemically, but again rinse it away VERY well, 10 to 15 minutes under warm 
running water using the toothbrush to make sure all the loosened oxides are 
removed.  Both Chip and socket.  Use q-tips to apply it to the socket.  If 
you can't see the effect right away, the tarnex has expired, it always 
smells like it has :-) and you need a fresh bottle.

Dry the board over a register about 24 hours & re-assemble. There is an 
angled corner to mark the chip, and a similar corner in the socket, match 
them up and press the chip back in, 20 to 40 pounds of push to make sure 
its seated.

This may not fix it, and its an involved process, so check the other usual 
suspects first.  I had to do it to mine once, about 15 years ago.  Still 

FWIW, I am a C.E.T. with 60+ years working in electronics experience.  
That, and about a buck 36 will get you a cup to go at the nearest 7-11.  
> Steven

Cheers Steven, Gene
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My web page: <http://coyoteden.dyndns-free.com:85/gene>
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