[Elecraft] KPA500 drive needed went up

[David Christ]

This morning my K4KIO antenna iced up without my noticing it.  When I 
started transmitting I got a high SWR fault on the KPA500.  I checked 
the SWR with my RigExpert analyzer and indeed there was high SWR on 
all frequencies.

I hooked the KPA500 to my dummy load and where I used to get a good 
500 W with 20-25 W drive I now only get about 400 W with 50 W drive.

Any ideas about what is going on?  Did I lose a transistor in the final?

David K0LUM