[Elecraft] Tx distortion

[Don Wilhelm]

If the filter is OK in receive, it will also be good in transmit.  The 
only things which differ are diodes D4 and D14 on the KSB2 board.

I would look for one of 2 things - RF Feedback and a bad microphone.

To check for RF Feedback, operate the K2 into a dummy load and listen 
with a monitor receiver using a wire for an antenna placed near enough 
to the dummy load to obtain an S-9 signal in CW.

To check for a bad microphone, the best way is to substitute another mic 
of the same kind.

A question - did you change from an Elecraft microphone to something 
else?  If that 'new' mic is a dynamic type, did you remove the bias 
resistor?  If the bias resistor is left in and a dynamic mic is used, 
the bias voltage will drive the mic diaphram off center causing it to 
"sound funny".

73,
Don W3FPR

On 2/1/2019 11:13 AM, mustang65 wrote:
> Hi!
> 
> I have hade my k2 about 14 years with number 4503 and it been a pleasure to
> build and operate it
> but now I got problems with distorsion on the TX audio.
> 
> It will usully work  fine when it been resting over the night but after a
> while the distorsion slowly comes.
> I t start with the base in the audio are reduced and then the treble are
> cracking up. It sounds like you driving a audioamplifier just  alittle to
> hard.
> The problem is the same with thek2/100 or when it removed from the k2.
> 
> I have used a 2 tone signalgenerator and loked with a scope att the signal
> after the ne602 and after the 10w amplifier
> and it looks fine to me but the bandwith of the scope is just 15Mhz so I
> might be missing something.
> 
> I have replaced u5, Q1, D2and some capacitors on the ksb2 board, tried to
> find any bad soldering but no luck.
> Can it be a bad capicotor in the  ssb filter or in the Tx signal path?
> 
> Grateful for any advise.