"tempus fugit" wrote in message
...
Hey all;

I'm working on repairing a Heath weather computer. Initially, none of the
funcitons really worked (temp, pressure, clock, etc.) I got it to the
point
last night where everything was working except the clock, which kept time,
but I couldn't actually set it. So, I (stupidly?) poked around a little
more
to try to get the clock going. I noticed a 4066 with some black stuff on
the
pins, and some weird voltages around it, so I pulled it out, fired the
unit
up, and checked the voltages again. They were still weird, but when I put
it
back in and turned it on again, the pressure and temperature stayed at 0.
I
was messing around with it again tonite, and the pressure and temperature
readings were more normal, but I noticed a couple of opamps (in different
locations) that were hot to the touch. There were no shorts in either of
them, and the voltages around them pretty much matched the schematic. I
now
get bad readings in the temperature (-40) and pressure (0). I'm guessing
the
opamps are at least part of the problem. Any idea why they are getting so
hot? Any other suggestions?

Thanks


From your description, I'd guess that your problem is intermittent, and may
be easily repairable.
When you say that there is "black stuff" on the pins of the 4066, is it just
tarnish or something else? If it's tarnish, then that could be the majority
of your problems. I assume that the ICs are socketed. If so, you can use
any of a few methods to clean the tarnish off the pins. The quickest is
Tarn-X, but you have to rinse them very well afterwards with clean water.
Don't leave *any* Tarn-X residue on the pins, since it is corrosive.
Another cleaning method is with a rubber pencil eraser. Be careful with
this, since it is easy to bend/break the pins.
What condition are the IC sockets in? They may need to be cleaned or
replaced if they are in bad condition.
How hot are the opamps? Are they just warm or really hot? If they're just
warm, it may be normal, depending on the circuit. Opamps usually are
low-level components... that is, they don't handle any appreciable power,
and usually run pretty cool.
Is the schematic of the unit available on the web anywhere, or can you post
it to the binaries NG? Might help with some suggestions to help you.
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