Thanks for the reply. More below.


"Trevor Wilson" wrote in message
...

"Phil Anderson" wrote in message
news:WMgZa.74397$Oz4.17285@rwcrnsc54...
I need advice on replacing the cooling fan on my GAS Ampzilla.
The current fan was too loud, so I tried slowing it down with
an
inline resistor. I got the voltage so low that the fan will
not
even spin unless I reach inside and give the blade a spin.
That
is both easy to forget and annoying to do.

**Er, use a smaller value resistor. Alternatively, you could
replace the fan
with a new one, which has better bearings and can cope with
lower Voltages.
You could also kick the fan into high speed, at switch on, then
allow the
resistor to come in, to drop the speed down.

As it stands, the fan has only one speed with the resistor in
place. I do not know how to "allow the resistor to come in"
later. The resistor I used was recommended at the time by the
amps designer, though he sounded very much like he was guessing.
With my luck, if I guess at another value, I will get one that
makes it loud again. I would just as soon start out by completely
replacing the puppy with something quieter, i.e., better
bearinged, as you advise.



Can I replace this with a computer cooling fan?

**Not usually. Computer fans are generally 12 Volt DC and pretty
crappy.
They're also difficult to add speed control to.

The Antec and Zalman fans in my computer are speed controlled, and
mighty quiet, too. More important, I am pretty sure the fan in my
'zilla is 12V DC.

What size do I
need?

**Same size as the oringal.

I guess I deserved that answer. My hope was that someone knew the
size offhand so I would not have to take the puppy apart once to
measure, and another time to put a fan in later when the order
arrives.


How about a speed control? My Ampzilla needs very little
cooling, but if the fan is all the way off it will overheat
after
a few hours.

**Papst make some excellent termperature-sensitive fans, which
would be
appropriate for your needs.

I've heard all sorts of good things about Papst computer fans, but
it seems like going the temp sensitive route is just a more
complex guessing game than is playing with resistor values. I
have no idea what temps I want. I do know the amp sounds better
when it is quite warm, and that a very slow turning fan seems to
move enough air over the heat sinks that it will never overheat
under the conditions I expose it to.

Which takes me back to wanting some sort of speed control. I can
turn it up just high enough to be sure the fan will spin at turn
on, but remain inaudible. And, on the off chance I decide to
drive it a lot harder than I do now, I can just turn it up further
still. A Papst that is not temp-sensitive might well fit the
bill, if I can just figure out what size to get.

Again, thanks for the reply.

Phil


--
Trevor Wilson
www.rageaudio.com.au