[Scott Dorsey]

wrote:
Thanks for the excellent info. I actually got inside of this amp this
weekend. Low, and behold: The culprit is the cooling fan. It's a
115VAC muffin fan that is run at a reduced speed until the unit heats
up. I'm not sure if this is a worn fan, or if the buzz is normal due
to the reduced voltage. When the fan is disconnected, the amp is dead
quiet. I considered just plugging it into 115VAC; but, running it
full-on would be annoying as well. Think a DC fan (of similar
dimensions and air flow rate) would work? Implemntation would be
simple: 115VAC-12V transformer, bridge rectifier, filter cap.... That
would preserve the dual-speed feature without getting into the temp
sensing end of it. There's plenty of room inside the case.

Go to Ace Hardware and ask for Zoom Spout Oil. This is Castrol OC-11
turbine oil that has been rebadged. Then get some high grade instrument
grease... in a pinch Mobil 1 racing grease will work.

Take the fan out and remove the plastic cover over the bearing.... on
some fans you may need to remove the label on it. Put a couple drops
of oil in there and work it back and forth. Press down on the blade so
the oil can get down the shaft and around the bearing. Then pack the
hole up with grease (it will only take a gram or two) and put the plastic
cover over it. This will keep the fan quiet for a couple more years
until you wind up having to replace it.

Digi-Key will sell you a Comair/Rotron replacement that will last forever.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."