[Elecraft] Problems with SSB Audio

[Geoffrey Mackenzie-Kennedsy]

Hello Paul,

My K2/100 (with KSB2) is about the same age as yours, and some time ago it 
started to act up - going as far as shutting down completely with just the 
display showing the last frequency to which it was tuned. In my case the 
problem was cured by removing the MCU U6 on the Control Board from its 
socket, and then putting it back again. The type of IC sockets used in the 
K2 do not seal the IC pin - socket connection, and corrosion can build up 
causing problems. Later, and I am not suggesting that you do this as it is a 
gruesome task, I replaced the socket supplied for U6 with a turned pin type 
which does seal the connection, but was not brave enough to change all the 
others!

Just a thought.

73,
Geoff
GM4ESD


----- Original Message ----- 
From: "Paul Wilton" <Paul.Wilton at tesco.net>
To: <elecraft at mailman.qth.net>
Sent: Saturday, November 12, 2005 3:11 PM
Subject: [Elecraft] Problems with SSB Audio


> 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
>