[Elecraft] Excessive SWR Faulting KPA500

[k2te at juno.com]

Bob,

You mentioned:

"Also you can bypass the KPA500 to STBY mode and check the system by 
observing the SWR on the K3."

I think you meant the KAT500 instead of the K3.  The K3 has to be
bypassed to work with the tuner.  Anyway, I have made some progress.  I
tried running through my dummy load and I got the run-up condition to
fault on 17 and 20.  I had to run reduced power since the load is only
rated for 300W.  The odd thing is that I had to use the tuner to make
things happy with the load.

Thanks to AI4VZ, I have the schematics for the KPA500 and the LPF
details.  The schematics are from 2011 or so and my gear is from 2017 but
I doubt the design changed significantly.

After testing with the dummy load, I re-connected to my patch panel only
to find that all the settings in the KAT500 were gone.  I had to retune
from 80 through 10; what a PITA!  However, my efforts were rewarded with
the amp working fine on CW everywhere except 12 meters.  I may have an
intermittent on 12 since the best I can do is 2.9:1 SWR after the tuner
shuts up.  Since both the 12 and 17 meter Vs are off the same feed point,
the 17 may be guilty as well; it settles around 1.9:1.

As for the amp faulting, I may have an RFI issue.  The 6BTV is only six
feet from the shack.  Another possibility: the fault surfaced when
running the amp on FT8.  The long duty cycle plus RFI may have done me
in.

Tnx for your help.

73 de Ed