[Elecraft] Problems with SSB Audio

[Paul Wilton]

Following some reports of bad audio (confirmed by self listening), I 
have been looking at my SSB adaptor in my K2.

So far I have reached the following conclusions
a)   Its not RF leakage - running with a Dummy Load still creates it
b)   If I monitor the RF output with my 100MHz scope, in CW the 
amplitude is clean and stable and I can change its level with the power 
control pot.  If I inject a single audio tone into the mic input, then 
the output is cleanish but keeps jumping in amplitude - approximate a 
few times a second.
c)    Looking around the SSB board, I make the following observations 
(with the power control pot on about 10W)

    The PWR CTRL line from Pin 6 on U2 slowly rises stopping at about
    5.5v after 5seconds.  At the end of its rail, it "jumps" a little.
    The ALC THR line from Pin5 on U2 goes instantly to the correct value.
    The Base of Q1 (VRFDET) jumps around
    The ALC line (Pin 2 of U1) also jumps around

It looks as if I have something amiss around the level control loop on 
the SSB card.  It works ok on CW.

My K2 has been working fine for a couple of years now so it is strange 
it has stopped.  Any suggestions where to look?

73

Paul
M1CNK