[Elecraft] Unstable AGC?

[PDouglas12 at aol.com]

Hello Elecrafters,

I have recently gotten back to digital modes with the K2.   It is a ten watt 
K2, not the 100 watt version.   Readers of QRP-L may recall my post about 
tracking down trouble with the KI02 which turned out to be a blown IC on the KI02 
board. 

Now, another problem has (re?) appeared.   I think it has always been there, 
and it led to my doing the mod to adjust the audio input AGC line on the SSB 
board some time ago.   But, it still is happening.   Here's the problem.

After adjusting the transmitter for either SSTV or PSK31, with any of the 
standard programs, the output stubbornly falls off to less than a watt, 
unpredictably.   When I first adjust the output for PSK31, for instance, the radio 
idles at 3 watts and jumps to well over five watts when there is signal--and can 
even jump to nearly 7 watts when the program goes into the steady tone before 
it changes over to transmit.   I'm keeping the K2 output setting via the front 
panel power control at five watts.   I'm not feeling any signs of heat 
underneath the K2, so I'm not thinking overheating.   The sound card is NOT unstable, 
as it puts out a stable drive to my old Yaesu 757GX (which I can drive 
consistently from 5   to 100 watts, without instability of output.)   The interface 
is a commercial interface with a back panel pot to adjust mike input (so 
there's not much chance the input is too low).   Any thoughts on this?   Is this a 
common problem?   Oh, and   I   note that switching to CW gives full normal 
output.   

Since the Yaesu is now 20 years old or so, it doesn't do Ham Radio Deluxe, 
which is a great way to operate the K2.   Otherwise, I'd just use the Yaesu with 
the power cut.   PSK31 doesn't need a 100 watt rig--five watts are almost 
always plenty.    I hate the idea of having to add another rig to the shack, just 
for digital modes and computer controlled operation.   Thanks for 
suggestions.

Preston Douglas WJ2V
216 Harborview North
Lawrence, NY 11559