[Elecraft] KPA500 270V Failure

[Bruce Forsberg]

Thanks to the 2 people who replied. Thanks to Keith VE7KW who had R16 (100
Ohm) SMD resistor fail on his PS board in his KPA500. I had the same
problem here. R16 tested open. It does not appear to be cracked or burnt,
just a failure. R16 appears to be a resistor that feeds the voltage
multiplier circuit for the 270V line.

Bottom line is my KPA500 is back in service.

Bruce, WB6IZG

On Sun, Jul 25, 2021 at 2:30 AM Bruce Forsberg <bruce.forsberg at gmail.com>
wrote:

> Today when using my KPA500 I switched it into operate mode from standby
> and received an error message of 270V ERR. This is the first time I have
> seen this error. I partially disassembled the amplifier and measured the
> 270V voltage and it is 70V, which is close to what the HV voltage measured
> on the front panel says. After finding some old outdated schematics on the
> internet it looks like there is a diode capacitor voltage
> multiplier circuit that takes the HV voltage of approx 70V and brings it up
> to 270V. I am assuming I have lost one of the diodes in the chain.
> Unfortunately Elecraft has used tiny diode packs and even put 2 of the 3
> packs between electrolytic capacitors on the board, which I will have to
> remove. Has anyone else seen this problem with their KPA500? And how did
> you go about fixing this?
>
> Thanks,
> Bruce, WB6IZG
>