You don't need to worry about the tarnish on the soldered component leads..
just the socketed components, such as ICs and transistors. If there are any
connectors that appear to be tarnished, then you should clean those as well.
BTW, have you checked the power supply output(s) with your multimeter? If
the supply voltages aren't correct, then you can't expect the rest of the
circuit to operate properly. How abot ripple on the PS lines? If there's a
lot of ripple, then there will be all sorts of chaos in the circuit.
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!
"tempus fugit" wrote in message
...
Thanks again.
Unforunately, I don't think I can scan the schem (it's huge for one
thing).
As for the voltages, they don't match up with what's indicated on the
schem
in a lot of places (even when I had most of it working), so I don't know
which to trust. I'll try removing the tarnish and checking for continuity
though.
Thanks


"Tweetldee" wrote in message
...
"tempus fugit" wrote in message
...
Thanks tweet.

The black stuff is actually on quite a few of the components - diode
leads,
resistors, ICs, etc. I never really looked too close at it, but it
almost
looks like black paint.
The opamps are HOT. They start out cold, and after about 2 minutes are
too
hot to touch. I have the original schematic, as well as the manual,
but
have noticed some errors on the schem (or the circuit board, I don't
know
which). One thing that I have noticed on a lot of components (mostly
xsistors) is odd voltage readings. There might be 5v on one side of a
bias
resistor, and 0.3v on the other (xsistor) side, but the xsistor checks
out
OK with a diode test (i.e., not leaky or shorted).

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.
--
Tweetldee


Undoubtedly, the "black stuff" that you see on the leads is tarnish.
It's
not dangerous to the components, but if it's interfering with mating of
component contacts, it will certainly prevent the circuit from operating
correctly. This could be the problem with the opamps.
There's something seriously out of whack if the opamps are too hot to
touch.. Don't allow it to run for more than just a few seconds until
you
get it fixed.. the opamps will be destroyed, if they are not defective
already.
I can't tell a thing from your voltage measurements without seeing the
schematic along with the voltages. It certainly would be a big help if
you
could scan the schematic and post it somewhere. Without it, it's pretty
much a waste of time here.
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in
the
address)

Never take a laxative and a sleeping pill at the same time!!