[Elecraft] Elecraft KPA500 sn 1910 dead

[Mike Maloney]

 I was gifted a KPA-500 in Aug. 2019.  Used about a month before It blew a main line fuse.   That was replaced and the amp remained dead.  What happened was the center bolt holding the power transformer was not torqued down properly and when the amp was tilted the core shifted into the low voltage supply and damaged it requiring replacement at the Elecraft shop.    Hopefully, that is not what knocked out your 12 volt supply?
73, Mike AC5P    On Monday, January 17, 2022, 12:52:13 PM CST, Jack Brindle via Elecraft <elecraft at mailman.qth.net> wrote:  
 
 I would not go by this. Many, if not most, KPA500s do not have noticeable hum when powered. Neither of mine do except for once in a while when the line voltage increases for a short time.

If yours does have noticeable him, you may want to check the tightness of mounting nut for the power transformer and retighten if needed (assuming it bothers you). There is a spec for the tightness of that nut. I believe it can be found in the assembly manual, if not also in the operating manual.

73,
Jack, W6FB



> On Jan 17, 2022, at 3:08 AM, Dave <dave.g4aon at gmail.com> wrote:
> 
> When the rear power switch is turned on, you should hear a hum from the
> transformer. The noise level from my KPA500 is quite audible from 2 or 3
> feet away with everthing else turned off. If you don't hear the hum, it's
> likely there isn't power reaching the transformer.
> 
> 73 Dave G4AON
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