[Elecraft] KAT-500 Unreliable Tuning

[Rick Lapp]

I have had the same issue with my KAT/KPA500, tuned into a good 1:1 SWR 
but faults when increasing power to about 450-500W. It would fault with 
an error of "VFWD too high for VSWR" in the fault table of the utility 
program. Trying different bands, dummy load tests etc, I isolated it to 
a combination of increasing power AND a HIGH BYPASS VSWR. This is the 
the 'untuned' SWR. If the tuner is seeing a high SWR (usually greater 
than 8-10:1 without tuning, even though it was able to match it to 1:1, 
the combination with high power would cause the tuner and amp to go into 
a fault mode. This is very repeatable.
However, as another posted here, I will be checking for evidence of 
arcing internally within the KAT.
Rick, KC2FD