"John A. Weeks III" wrote in message
...
In article , Phil Anderson
wrote:

In short, it worked, I replaced the fan, I moved, and now it
hums.

At the risk of sounding like some sort of electronics school
exam:
How many possible hum sources are there in the above scenario,
and
what can I do to troubleshoot them and/or rule some out?

It would be nice to rule the fan in or out right away. You can
probably run the amp for a short period of time without it. How
about disconnecting the fan, both wires, and see what happens.
If it still hums, then it wasn't the fan, and you likely have a
power or grounding issue.

Some followup before I disconnect the fan tomorrow night. Mark
Zacharias asked if the hum was in one or both channels. After
turning it back on to check, I wrote the following to him, and
wonder if it changes your fan suggestion at all:
quote:
This turns out to be a little weirder than I thought. When I
heard the hum last night, it never occurred to me it might be from
one channel only. I figured this was a ground hum, and such
things always occur in both channels, do they not? The pop came
from the left channel, that I was sure of, but nothing more.

So, I turned it on again tonight, with a listener staged by the
right channel. She heard nothing. I heard another pop from the
left channel. I moved over to that speaker, and heard only a very
slight hiss. The hum is coming from the amp itself!

I am far from expert in any of this, but I've got to admit this
worries me a lot more than did the thought I had a ground hum to
diagnose. Also, my power meter lights no longer work. I am
certain that they worked in the old apartment, all those months
ago. I do not recall if they worked last night or not. I turned
it off pretty quick and do not recall noticing.

What is my next step?
end quote

Phil