[Elecraft] KPA-500 Loud Hum

Ron D'Eau Claire ron at cobi.biz
Mon Sep 26 23:00:40 EDT 2011


Check the other case screws, particularly the ones holding the left side
panel (the panel with the feet closest to the transformer). Unlike the K3,
the KPA500 uses steel panels for greater strength to support the
transformer. They, of course, want to vibrate from the magnetic field
leakage around the transformer. If a screw is loose, the panel can vibrate
more easily and make more noise. 

If that doesn't do it, my next step would be to try tightening down the
mounting bolt a bit more. 

"Fairly loud" is hard to quantify, of course, Hi!, but I can say that mine
when not transmitting is much quieter than the fan at minimum speed. 

73,

Ron AC7AC

-----Original Message-----

Noted that my new amp is making a fairly loud humming noise when not under
load, and a much louder hum when under full power. New thing, have not heard
this before, power output still good, but noise is really concerning.
Removed top, nothing loose, should I try retorting the xformer hardware or
look elsewhere?

Cordially, 
Bruce J. HowesW1UJR
www.w1ujr.net 

Sent from my iPad
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