Hi Chris,
Unless there is something arcing, I would guess RF getting into something.  
Maybe the control cable to the auto tuner?  


73,
Gary K9GS
-------- Original message --------From: Chris Hallinan <challi...@gmail.com> 
Date: 2/23/18  11:42 PM  (GMT-06:00) To: "<elecraft@mailman.qth.net>" 
<Elecraft@mailman.qth.net> Subject: [Elecraft] KPA500 Faulting on high SWR on 
power rise 
Greetings from southwest Florida.

My KPA500 is kicking out with REFL HI warning (high SWR).  But here is the
strangeness. My setup is K3->KPA500->40' coax->MFJ 600W remote tuner -> 4:1
balun -> open wire feedline to 80-meter doublet.  In words, I have a remote
autotuner feeding an 80-meter doublet fed with 600-ohm open wire line.  A
Balun Designs 4:1 balun provides the interface from the open wire line to
the tuner.

With the autotuner tuned at low power, the SWR shows 1.5:1 on my KPA500 and
external SWR meter.  As I run the power up to 300, 400, 500 watts,
somewhere in there all of a sudden the SWR instantly jumps off the scale,
into the red LEDs on KPA500, and it faults.  It's as if the SWR were
dependent on power.

Even stranger, when I back the power off to say 250 Watts, holding key down
the SWR is stable in the green (<1.5:1), but when I key it at CW rates, the
SWR bounces into the red on every dit and eventually faults, when at steady
state key down it never leaves the green zone!

I fear it is the tuner falling over, but it should be able to handle the
power.  I see this on all bands from 80-20.

Operating into my 20-meter resonant vertical, with no tuner, everything
works fine.

Any ideas or hints on how to correct this?

Thanks,

Chris
73 de K1AY


-- 
Life is like Linux - it never stands still.
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