[Elecraft] KPA500 Hum and Sticky Relay?

[Geoffrey Downs]

I did as you Roy but if I press my ear to the top of the KPA500 case I can 
hear a faint hum. It is the same with my 12v linear power supply underneath 
the bench. I do not believe it is a fault but fairly normal for linear power 
supplies. Occasionally both the KPA500 and the power supply under the bench 
will hum more loudly for a short time. I have always put this down to 
variations in the mains supply waveform as referred to by Ian GM3SEK in his 
earlier message.

As regards the "sticky relay" phenomenon - I have experienced this a couple 
of times. Switching the KPA500 off and then back on again has cured it.

73 to all

Geoff
G3UCK

-----Original Message----- 
From: Roy Morris
Sent: Tuesday, September 27, 2011 7:33 PM

  I snugged the transformer
against the rubber bumpers, and I can see light between the transformer and
the Z-Bracket.  I have not experienced any hum at all.  Roy  W4WFB