I’ve ended up using a 6 Volt DC wall wart. This has slowed the fan down
enough to reduce noise to acceptable levels, while still pushing enough
air. I thank you for all your suggestions but having several wall warts
around this was the easiest and most cost effective. The wall wart has
double the amps the fan needs but from your great posts I can see that
this won't hurt the fan it will only draw what it needs.

My last amp was a Mesa Boogie Mark IV that came with a fan. It has four
output tubes 6L6GC type or two 6L6GC and two EL34. The fan was mounted
under the tubes against the inside amp wall facing up towards the bottom
of the chassis. This worked because the power tubes were socket mounted
with the sockets being attached to the chassis.

The amp I am now adding a fan to is the Mesa Boogie Studio 22+. The
output tubes are two EL84. Their sockets are PC board mounted and the
PC board is mounted with standoffs about half an inch inside the bottom
of the metal chassis. The back panel of the chassis on the rear top
back of the amp has vents which are vertical slots cut in the metal on
the right side where the tubes are.

My thinking is that if I mount the fan below the tubes facing up into
them towards the bottom of the amp chassis that probably it won’t be
doing much good. There are holes cut in the chassis bottom where the
tubes go through to the PC board that leave about three eights of an
inch all around once the tube is seated. Cooling the bottom of the
metal chassis isn’t going to do much good and not much air flow is going
to get through to the PC board.

As a result since there are vent slots at the rear and you can clearly
see the PC board back edge and the tube sockets which are about an inch
away from the back. Would mounting the fan so that it’s top half covers
about half the vents with some vents left right and left and the other
half of the fan hanging down below the bottom of the chassis, be a
better idea.

If so would facing the airflow out of the amp be better so that it pulls
hot air out from inside that is circulated in from the bottom as opposed
to pushing air into the chassis, which will probably take heat away from
the sockets but build it up somewhere else?

Thanks.

On Wed, 13 Apr 2005 18:19:33 -0400, ren wrote:

If so would facing the airflow out of the amp be better so that it pulls
hot air out from inside that is circulated in from the bottom as opposed
to pushing air into the chassis, which will probably take heat away from
the sockets but build it up somewhere else?
IMHO Pulling *Hot* air will shorten the life of the Fan Electronics.
Push cool air near the base of the tubes. This cools the socket area
and might reduce heat conducted to the PCB that causes that darker
color around hot components.

Heat wants to rise. The fan should *help* natural flow.
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