Hi, Phil.

I'm still not sure from your response whether the hum is coming from one or
both speakers, or a mechanical noise from the amp chassis itself.
If it's a mechanical noise, one can use a listening instrument such as a
medium length screwdriver, and physically touch it to a part of the chassis
while holding the handle to your ear. Works like a stethoscope, and I find
this useful to help isolate mech noises.

To be truthful I'm not very familiar with the larger 'Zilla, but I'm pretty
sure I have a schematic somewhere.

It's not uncommon for lamps to fail after a piece is moved from one location
to another. The old filament is often very weak from age and the slightest
vibration is all it takes for it to die.

Mark Z.

--
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have rendered my regular e-mail address useless.


"Phil Anderson" wrote in message
...

"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