Re: The long HP1980B repair story...

Robert Obermayer <robert_ng@xxxxxxxxxxxxxxxxxxx> wrote in
news:4jgv0vF82ahaU1@xxxxxxxxxxxxxx:

Ohmster wrote:
I have no idea of what caused the problem. Faulty IC I would imagine,
but I did indeed enjoy reading the story. You did a good job, Bob.

Might be, but what causes a IC to work flawlessly for 20 years and
then suddenly fail?

Uh parts just fail, dude. That's just life. Nothing is expected to last
forever, although low voltage and low current ICs sure can last a very
long time. Who knows what made it fail. Maybe the mixture was not as good
as it could have been at the factory the day the part was made and it did
not last as long as other ICs did. Maybe the case had small flaws in it
near the leg openings and allowed moisture to enter the package. Maybe
the etching was a bit too close when it was made and it finally gave out.
Who knows, don't take it personally.

I think (but cant really remember exactly) that the problem appeared
while adjusting focus and that i heared some click (probably one of
the many relays in there).

Might be totally unrelated. Maybe you messing around in there caused a
small arc to jump. Hard to say, doesn't really matter anyway.

I already checked if the signal goes anywhere close to a high voltage
wire (that could spark to it if moisture was present) but didnt turn
out to be so.
I found the +18kV-wire being rather close to unrelated wires however
and tied it away from them just to be safe.

It is always good to be safe.

Btw, thats how it looks now:
http://www.hobbyelektronik.org/robert/1980_ok.jpg

Looking good there Bob!

--
~Ohmster
.

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