[Elecraft] K2 - Need tips on troubleshooting audio intermittent problem

[Don Wilhelm]

DW,

Additional information about Receive Signal Tracing when your problem 
occurs.  Yes, that can be done using the RX signal tracing steps in the 
manual Appendix E.  You will need a high level signal generator - the 
xtal oscillator shown in the manual will do just fine, or the attenuated 
output of an MFJ259 antenna analyzer.  You want 0.14 volts at the 
antenna as read on an RF probe (2.8 times that if using the peak to peak 
RF voltage on an oscilloscope.

Caution:  The addition of diodes D40 and D41 have made the IF Amp 
Saturated Output results to be unobtainable (the IF Amp will not 
saturate with the diodes in place).  You can temporarily lift one end of 
those diodes and go on with the tracing.

The first stage where you find the RF voltage significantly less than 
expected is the troublesome stage - any reading after that point are 
meaningless until that problem is resolved.

Good luck on it.  Intermittent problems are difficult - one never know 
whether the problem has been solved or it just went away to rear its 
ugly head at a later time..

73,
Don W3FPR

On 9/25/2012 5:20 PM, dw wrote:
> Hi Gang,
> I got my K2 a couple of years ago.
> Once in a great while I would notice the audio volume drop to about 30%.
> It would typically happen after I had moved the unit or had the cover
> off doing filter alignments.
> I found I would simply tap the unit and the audio volume would be
> normal.
>
> I figured I would eventually get around to checking the circuit when I
> had the unit cover off again.
>
> Well last week I replaced the audio and RF gain pots.
> Those are working sweetly.
>
> At the time I had the control PC dis-assembled I did some re-soldering
> of all of the joints I could find around the LM380.
>
> I thought I had it fixed by doing that but last night it did it again.
>
> Any hints or tips on best way to troubleshoot this?
>
> Maybe tracing the audio circuit with a signal source at the time it
> drops?
> Your suggestions welcome!!
>
> Thanks
> N1BBR