[Elecraft] [K2] Intermittent KPA100 "not inst" and Info 080 issue - Humidity??

[Bill Coleman]

In the last couple of months I diagnosed and fixed a problem with the KPA100. There were two failures -- one was U6 -- EL5146C which was shorted internally and kept the KPA100 microprocessor from receiving the +5 volts it required. The second were failures in the 1N5711 Schottky diodes D16 and D17 -- they failed as partially working.

I recently operate the K2/100 during the CQWW RTTY and it didn't give me any trouble. However, today I got into the shack to work a couple of contacts at lunch, and I'm greeted with Info 080.

A little more background -- even after fixing the issue, I would occasionally see an "not inst" error when pressing the Ant 1/2 switch. Sometimes the KAT100 wouldn't light up immediately when switching the K2 on. When it did this, I'd generally see the "not inst" problem. Cycling the power switch would generally cure the problem.

I saw this issue once before, right before Field Day. I'd set up my rig in my camper, and then the next morning it gave me Info 080. At the time, I believe part of the problem was due to humidity. If I leave the rig on, eventually the problem seems to resolve itself.

There's something that definitely seems to be sensitive to humidity and the action of the AUXBUS. 

As I write this, it is 75 degrees F and 87% humidity in my unheated storage room shack. The K2 initially had several segments in the display that were only partially dark, but now they are dark black. Initially, there was no sound out of the speaker, and it would "tick" when I turned the main tuning dial. Perhaps if I wait long enough, it will eventually dry out.

Any clue how to diagnose this problem? Are there components which are particularly sensitive to humidity? Why does this affect the AUXBUS operation?

Any help or suggestions would be greatly appreciated.