[Elecraft] KPA 500: No Output

[dave ingebright]

Hello-- I have a 3 yr old KPA500 that has just exhibited it's first problem. No amplification! I am remote controlling it via the remote client over the internet from 2000 miles away. Nothing has changed in the remote shack and no wiring has been disturbed. There is no output from the KPA on any band. I can see the 72 Volt B+, and the temp of the heatsink, and I can control the fan speed, so I have control of the unit. The client shows the exciter power through the amp and the SWR. There are no alarms and I have hit alarm reset and had the power plug pulled and reset.  I'd guess the PTT line is somehow open but... asking if anyone has had a similar problem.
tnx de dave
WB7ELY
My KPA500 page: https://www.valhallatreefarm.com/WB7ELY/kpa500/kpa500.htm