[Elecraft] Problems with SSB Audio

[Paul Wilton]

Geoff,
I did try this but it didn't solve it.

What I have found is that I was wrong in believing the CW was OK - its 
not - it has a very raspy signal to it.  So I will try to track that 
down first.

I am confused about the behaviour of U2 on the SSB board - it seems to 
take a long time to ramp up if it is setting the PWR level.  However, 
before I worry much more about this one, I'll try and track down my 
raspy CW signal first.

73

Paul

Geoffrey Mackenzie-Kennedsy wrote:

> 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
>>
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