[TMC] Rotron blower

[Robert Nickels]

I'm looking for tips on noisy Rotron blowers, the one in question being 
used in a PAL-350 amplifier.   I was told that bearing replacement is 
often needed so I got some new bearings and replaced them, but the 
rattly metallic noise continues unabated. The position of the armature 
between the end bells seems to be determined by shim washers in each 
end, and I kept the same number in the same place as originally, but is 
this something that is tweaked for each motor?    I'm sure I didn't get 
the bearings in precisely the same position on the shaft but assume they 
move as needed when the end bells are attached and tightened.   The 
motor starts and runs fine and produces plenty of air, it's just this 
mechanical noise in addition to the expected white noise of normal airflow.

73, Bob W9RAN