[Elecraft] Tx distortion

[Don Wilhelm]

Mike,

With RF and microphone out of the way, I would look to either coupling 
capacitors in the AF path (C20, C32, and C34) or the Speech Compressor 
IC for the problem.

Unfortunately, the '2165 speech processor IC is no longer available - 
the KSB2 was redesigned to use the '2166 IC instead, but it is not a 
drop-in replacement, and if that turns out to be the problem, it means 
buying a new KSB2 board.

73,
Don W3FPR


On 2/2/2019 10:07 AM, mustang65 wrote:
>   
>    Many thanks for the answer and good to know that I can rule out the filter
> as the problem.
> 
>    I have not change anything in my setup that I used for severel years and
> that is main reasen
>    I believe something has happend to the k2.
> 
>    All the tests I done so far has bean made in to a dummyload and a icom 735
> as receiver.
> 
>    I use a shure sm58 microphone that is connected to symetrix 528e micpreamp
> , voiceprocessor that
>    drives the k2. I also have a Icom microphone that I connect directly to
> the K2 and it do not make
>    any difference on the distorsion. Both this setups have worked nice for
> many years.
> 
>    If I use the icom 735 as transmitter and k2 as receiver it still works
> fine both with the icom  microphone or the symetrix unit and shure
> microphone.
>    
>    The strange thing is when the k2 has been turned of for a couple of hours
> and then
>    start to transmit the tx audio is mutch better then it comes like you
> slowly turn upp a pot
>    the audio gets thinner and the distortion increases.
> 
>   I monitor the driving signal from the symetrix unit at the same time to
> rule out that as a cause.
>   Looked for cold soldering on the ssb bord.
> 
>   I have also looked for any components to get varm and so far it is just Q6
> on the RF board that gets
>   araond 122 degrees Fahrenheit that do not seems like a problem.
> 
> 
>   I have meassured D1 and D14 and looks ok. Can Q2 on the ksb2 board cause
> this problem?
> 
>   73 Mike sm3xgm
> 
>   
> 
>    
> 
> 
> 
> 
> 
> 
> --
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