Steve,
Definitely a noisey fan! There is a resonance heard with something
else. Mounting the amplifier on a rubber pad may help. Also, mounting
a rubber gasket under the fan mounts may isolate it from the rig case.
You have some noise there like dry or bad bearings. If the thing is a
muffin type fan, you can peal off the foil label and get to the
bearing. A teflon containing oil, like Triflow (TM) can revive a dry
fan for a couple of years or more. It is a spray on, oil product. You
may also have imbalance in the fan blades. If you can borrow a
Strobotach, (strobe light with variable flashing sequence related to
RPM) you may be able to find out if it is the blades or a loose
bearing. If all else fails, a new fan probably is not all that
expensive. If you find out the flow rate of the old, you may be able to
find a local equivalent.
GL and 73,
Stuart Rohre
K5KVH
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