[Coco] RE: 512 Upgrade

[Andrew]

Longshot, but check for cold solder joints on the board itself. Also, 
try putting the 128K back in, jumper the caps you removed back in place, 
and make sure the machine still works as a 128K machine. If so, then it 
has to be the board, but if not - your CoCo may have problems of its own.

Check CoCo3.com and/or Google for the CoCo 3 service manual - it might 
help out.

Also, check for lifted traces, corrosion on solder joints, possible 
broken connections on the chips themselves and any other hinkyness with 
the board. Boards that old can get flakey. Plus, from what I remember, 
the RS upgrade wasn't the best to begin with.

You might also try (though I have no clue if this is possible or if it 
can be done with the board?) to pull out 1/2 to 3/4 the memory from the 
board - what I am thinking is that one or more (but only maybe a couple) 
of the RAM chips are bad, and maybe you could get it to run (though 
maybe not perfectly, but enough to boot) as a 256 or 384K "upgrade". If 
so, then maybe swap in one chip at a time in the banks and see when it 
crashes/hangs. If this is even possible, of course (maybe someone here 
can tell us more if this is possible?)...

-- Andrew L. Ayers
    Glendale (Phoenix), Arizona