[Elecraft] KPA500 Faulting on high SWR on power rise

[Don Wilhelm]

Chris,

You have seen several posts with good advice.  If you want to do an easy 
test to localize where the failure may be, you can do it with a dummy load.
First put the dummy load at the rig.  Check to see if all is OK, if not, 
blame the rig.
Then check the coax - connect the dummy load at the end of your coax 
(replacing the remote tuner).  If the problem shows up, then blame the coax.

If all is still OK with the dummy load at the end of the coax, you can 
blame the tuner, balun or the antenna or RF getting onto the coax outer 
shield.  Look for evidence of arcing, make sure all connections are 
solid - then try adding a K9YC type current mode choke near the entry 
point entry to the shack to choke RF coming in on the outside of the 
coax braid.

73,
Don W3FPR


On 2/24/2018 12:42 AM, Chris Hallinan wrote:
> 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.
>