[Elecraft] Q22 post mixer amp problems

Mon May 5 13:32:01 2003

I have also been concerned with what seemed to be low receive levels with my K2
- after hearing all the chatter about Q22 (and only having a few 40m broadcast
stations ever manage to 'peg the meter' full scale) I'm tempted to remove Q22,
run fine sandpaper over the leads, and reinstall Q22. During QRPTTF everyone
was giving me an S5 and they were all pushing about S1-S3 on the meter with the
Pre-amp on. I gave out an S7 to one fellow when he actually managed to get an
S5. I know it's a relative scale, and it goes back to the AGC voltage setting
and recalibrating S Lo and S Hi... but I'm going to try both now (Q22 and AGC).

Thanks,
Daniel/AA0NI


--- Bob - AG5Q <[email protected]> wrote:
> I also found that my K2 had very low gain at first. I could barely hear only
> a few signals.
> 
> Finally, using DC voltage measurements, I found that Q22 wasn't conducting
> any current. Even though the solder joint on the emitter
> lead looked good with a 3x magnifier, it wasn't. After resoldering the
> emitter, everything worked fine.  Several people have
> reported a problem with Q22. I wonder if there might be a film on the leads?
> 
> 73/ Bob - AG5Q
> 
> 
> ----- Original Message -----
> From: "Wallace, Andy" <[email protected]>
> To: "Ken Wagner" <[email protected]>; "Elecraft Reflector"
> <[email protected]>
> Sent: Monday, May 05, 2003 8:14 AM
> Subject: [Elecraft] Q22 post mixer amp problems
> 
> 
> > -----Original Message-----
> > From: Ken Wagner [mailto:[email protected]]
> >
> > I noticed that the gain was  *way* down and
> > that the Rx current draw was now 480ma. It smelled kinda hot as well.
> > Sometimes prior problems are helpful. On an earlier K2, I had
> > a problem with > the Post-mixer Amp circuit and this was
> > producing somewhat the same
> > symptoms, except for the increased current draw.
> > I removed Q22 figuring I would have to replace it.
> > I  checked Q22 with a meter and it seemed OK. I put it
> > back in. Now it works just fine, thank you. I could spend hours
> > speculating what was wrong, but I won't. It works fine now.
> 
> I find this _extremely_ interesting - can you tell me what you
> found on the previous rig, as well?
> 
> When I built my K2 (#31xx) a few months back, I had problems
> in the exact same area. Resoldering Q22, RFC(16?) and a nearby
> cap brought it to life. (Unfortunately I didn't try one at a time.)
> 
> The symptom was that the rig was fairly deaf; no abnormal
> current draw but to get S-9 with the preamp off I had to
> inject about 350 uV at the antenna jack!
> 
> After resoldering, measurements very closely matched those in
> the ARRL K2 review. Been fine since. I did rewind the RFC
> and replaced the cap just in case, but left Q22 in.
> 
> So this is interesting - wonder if something is up with the
> batch of Q22s in stock?
> 
> Andy
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