[Elecraft] KPA500 PA DISS fault -- FIXED

[Rajiv Dewan]

I had the same fault and it is now fixed.

Recap:  My KPA500 started faulting and showing PA DISS error message on 
the LCD display even when feeding into a good dummy load.  For all bands.

Based on the feedback, I talked to Elecraft Support.  They thought there 
might be a short in the RF circuit.   They did not offer any specific 
support.

I took the RF module out. Sure enough, it was obvious the Toroidal 
Inductor L5 had failed. There was a lot of soot on the board, especially 
around this part. The toroid itself seemed to have overheated and the 
magnet wire was blown open.  This is in the T/R section of the combined 
LPF-TR board.

I cleaned the board with IPA and checked the close by components. They 
seemed fine.  I had a T2-68 toroid and 24ga magnet wire that the 
schematic called for.  I rewound a new inductor (51T), measured it at 
15uH (higher than the spec 13uH) and installed it.

The amp is working now.

I can try to post some photos if that helps.  (can one do that on this 
reflector?)

Best,

Raj, N2RD

On 7/16/2023 10:35 AM, Glenn Anderson wrote:
> I had the same problem about a year ago.  It's a problem with the 
> output PIN diode switch. There will be a burned toroid in the output 
> switch circuit. I sent mine back for repair. It's been working fine 
> since.
>
> Good luck,
>
> Glenn WB5TUF
>
> -------- Original message --------
> From: Rajiv Dewan <rmdewan at gmail.com>
> Date: 7/16/23 08:45 (GMT-06:00)
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] KPA500 PA DISS fault
>
> Hello,
>
>   My KPA500 developed a PA DISS fault right the start of the VHF
> contest operating FT8 on 6m.  It is:
>
> * showing this message on all bands.   The antenna is fine.  (1.2 SWR)
>
> * same fault even when feeding a good dummy load
>
> * I smelt acrid smoke :(
>
> What do you think I should check or do?
>
> Thanks for any tips,
>
> Best,
>
> Raj N2RD
>
> -- 
> --
> Rajiv Dewan, N2RD
>
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-- 
--
Rajiv Dewan, N2RD