[Elecraft] K2 - Need tips on troubleshooting audio intermittent problem
Don Wilhelm
w3fpr at embarqmail.com
Tue Sep 25 17:54:00 EDT 2012
DW,
You have a bad solder connection somewhere, and it is not necessarily in
the audio section - it can be anywhere in the receive chain, including
the noise blanker and the KSB2 option if those are installed.
Use a constant signal source such as a XG1, XG2, XG3 signal generator
set for a 50 uV output. Tune in the generator output and make some
observations - does the S-meter drop when the audio drops? If so, the
problem is prior to the output of the IF amplifier. OTOH, if the
S-meter stays constant and the audio drops, the problem is after the IF
amplifier output.
I can't help much with specifics beyond that to further locate the
problem. You might "shotgun" it by re-flowing the soldering with a hot
(750 degF) soldering iron - add a tiny bit of flux if necessary.
Examine your solder connections carefully. I know nothing of your
soldering capability, so please no insult if you are an expert. If your
soldering level is expert, the most likely is that you missed a solder
connection somewhere.
A good solder connection will have the solder flowing out to an almost
invisible edge on both the solder pad and the component lead. There may
be a small concave fillet at the connection. If your solder looks more
like "balls" (convex) or there is a ring around a component lead, that
is a problem.
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!!
>
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