The above diagram came through all messed up. Maybe you could say the
diagram in words? I would appreciate it. My guess as to what you
say is cable to preamp in---preamp out to computer in ---computer out
to speaker.
Yes. Basically, I wanted an RCA cable plugged into the preamp,
so you'd have the male connector on the end to work with. Then
try the hum test, with the male connector. For stereo, there
would obviously be two cables, and you could individually test
the left and right channels. Listen for the hum, on the
computer end.
If it looks like the preamp is dead, and the casing has screws, perhaps
you could open it up and have a look inside. If there was
something like static damage to the amplifier, there would be
nothing to see, so a visual inspection doesn't promise you'll
find a problem. You'd only be looking for the simplest of faults,
such as something that broke loose because of mechanical damage.
Electronic designs have varying sensitivities to static electricity.
Some RS-232 chips, are good to 15,000 volts. They did that, because
twenty years ago, RS-232 level shifter chips used to "drop like flies".
I had to replace several at work (MC1488/MC1489 series), and they
weren't being abused or anything. Someone finally decided to do
something about it, and the modern versions are pretty good.
Intel USB ports are good to 5KV to 6KV. Not quite as good as
the RS232 chips, but still pretty good.
There are some MOSFETs you used to be able to buy, which
could be destroyed with as little as 40 volts of static
electricity. Those came with the leads of the transistor
wrapped in a steel band. You soldered the component into the
circuit, and then removed the spring steel band afterwards. The steel
band was there to prevent static from getting them.
I had some ICs at work, which due to a design flaw, had no antistatic
protection (no clamp diodes) at all. 50% of those would die,
as they slid down the inside surface of an antistatic IC tube. So that
is an example of how sensitive some electronic components can be.
If a part can be ruined, while housed in antistatic plastic,
that is pretty sensitive. My buddy and I, designed clamp circuits
and sockets for those chips, and once you had clamp diodes on all
the logic signals, the chips were robust and wouldn't fail. But
until you could get them into a protective socket, 50% of them
would die. They were perhaps $22 a piece, and for us, a large
waste of money. Fortunately, they weren't shipped as part of
a product design, but as a debugging aid we provided with the
product. A field tech would carry one of those, and connect
it to a piece of equipment to be debugged. So that is the
absolute worst piece of static sensitive stuff I've worked with.
A big difference between those, and the chips that can take a
15,000 volt static electricity insult.
There is no way of knowing how static sensitive your preamp is.
I only mention the above examples, to show the wide range of
performance available. Some electronic devices are well
armored against static, and others, not so much.
Paul
