[Elecraft] KPA-1500 failed!

[rocketnj at gmail.com]

I talked to Peter on the phone. He has no bias current when amp is transmitting with no power applied (key on SSB without talking. He is reading 54 volts and has tried power cycling amp from power supply switch and reseated all cables. Definitely BAD distortion on SSB (we are close enough to hear each other). Looks like one RF device let loose and it is dragging down the bias voltage. That is my guess.

Dave wo2x


-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Wes
Sent: Saturday, February 16, 2019 9:49 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KPA-1500 failed!

I think a two-tone test is the best evaluation tool..  The generator is built into the K3 if you have another receiver that you can use to listen to the amp output.  I use an SDR-IQ which is a very nice tool for this but any other SDR would do.

Sorry for your pain.

Wes  N7WS

On 2/16/2019 7:28 AM, lists at w2irt.net wrote:
> I was operating in the ARRL-CW contest this morning and on 20m, with a 
> 1.2:1 SWR on the Yagi, all of a sudden I saw my power drop to about 
> 450-500W with about 40W in. Worked a few stations but not as easily as 
> when I turned everything on this morning. Switched over to phone and made a few contacts.
> Audio is fine barefoot with 100W out of the K3s-which suffered blown 
> finals itself during CQWW SSB last fall, but with the amp in I got 
> reports that my audio was badly distorted.
>
> Before I send it in, is there anything I should look at or any 
> diagnostics I can easily perform? For the cost of this, I'd have 
> thought protection would have kicked in to prevent anything untoward 
> from happening. I'm in complete disbelief, to be honest.
>
> ---------------------------------------------
> 73 and Good DX
> Peter, W2IRT
>

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