[Elecraft] KPA500 Hum

[Ron D'Eau Claire]

What you are describing is very unusual, Mike. 

Typically, one will hear some hum from the transformer with  the "key down"
(full 500 watt carrier). It is most pronounced when using the green
transformer tap (lowest line voltage input). Normally there is no hum with
the KPA500 off, or when running the KPA500 at low duty-cycle loads such as
SSB, even at full peak power output.

I'd drop a line to the elecraft support reflector and see what the
Ele-guru's say.

73, 

Ron AC7AC 

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

My KPA500 now seems to have the hummms.  It comes and goes whether the 
unit is on or off.  It does go away when you turn off the rear switch.

I noticed someone changed the tap and that appeared to fix the hum.

I am running the amp on 110V.  My actual wall voltage is 119V.

I did not notice this at all while I was at our Montana home over the 
summer.

Mike W0MU

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