[Elecraft] K2: KPA100 Trouble

[Jim KO5V]

Good Morning,

My K2 Twins have been working great for the past 11 months. I usually run about 90-95W.

This morning when I turned on the rig the room was probably about 55F. I immediately worked a loud DX station. The second QSO a few minutes later was going just fine, but after about a minute, I received a brief "Hi Refl" error, followed by "Hot PA" - which wouldn't go away until I pressed a button (menu, I think). There is no power output. The fan runs constantly on "Hi", and will not shut off. Resetting the power by turning off the K2 and the power supply has no effect.

When I attempt to tune @20W, I will get the same error message (sometimes "Hot PA" only), or the K2's display either shows "20" and nothing else, or "20" plus a brief SWR reading. The KAT100 makes no noise, and it's tuning lights are either erratic, or off. Sometimes it comes out of "Tune" after a few seconds, sometimes I have to press the button a second time.

I turned the power down to ~8W, and the KAT100 tunes the antenna normally (@2w). I attached my 61ohm dummy load, and behaviors at both power levels are the same as with the antenna.

I opened up the KAT100, and found the final transistor mounting screws a bit loose (~1/8 of a turn - I had re-tightened them several months ago). I checked the diodes, and they were all OK. 

I thought that maybe the loose screws might be the trouble, but there was no change.

I have seen references to cold temps causing trouble with the logic, but 55F doesn't seem that cold - or does it?

I thought I would ask for some advice before I start troubleshooting. I think the K2, and KAT100 are fine. 

Thanks in advance for any suggestions.

73, Jim KO5V