Vintage Synth Repair

On Friday 30 June 2006 12:34 pm, sputnik979 wrote:
> OK guys, so you're saying bad connnections.
> But let's assume, what in fact may be very much true, that my tech has
> checked everything, according to the schematics, and the problem still
> persists and we cannot locate it. What to do? Which direction to go?

Been there and done that one,  for sure -- "I've checked *EVERYTHING*!!!"  
Only it turns out that I hadn't,  that I'd missed something subtle,  or at 
least not apparent to me because I'd gone at something with some assumptions 
in place that weren't apparent to me either.  I hate it when that 
happens!  :-)

Is there in fact a write pulse getting to the ram chip?  When it's needed?  
And are all of the other signals at that chip correct for what it's supposed 
to do?  Hard to tell without a logic analyzer,  for sure.

And battery corrosion is such *nasty* stuff,  it just eats copper traces right 
up.  Your problem could be in a plated-through hole for all you know.

Worse yet,  it could be something that doesn't show up all the time,  it's bad 
when the board is in the normal operating position but when you move things 
to get at it to test stuff,  it looks okay.

Something like that,  anyhow.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin