Posted by
aj4tf on
Jun 16, 2011; 10:26am
URL: http://elecraft.85.s1.nabble.com/K2-Update-K2-100-loss-of-power-control-long-post-tp6465960p6482470.html
New diodes arrived yesterday, thanks to Richard at Elecraft. After
installation and re-calibration of the SWR/wattmeter, everything looks
good, I made two quick contacts on 20m PSK31, one in Greece, the other
in Slovak Republic.
Thanks again Don, Richard, and Elecraft!
73, David AJ4TF
On Sat, 2011-06-11 at 19:48 -0400, david wrote:
> Don,
>
> Thanks for confirming my diagnosis. I *usually* remember to disconnect
> the antenna when I am not operating.
>
> I assume that the standard 1N5711 will work, Elecraft doesn't screen
> them for any special characteristics do they?
>
> As always, I'm sure I'm not the only one that appreciates the knowledge
> you bring to the Elecraft community.
>
> David AJ4TF
>
>
> On Sat, 2011-06-11 at 18:13 -0400, Don Wilhelm wrote:
> > David,
> >
> > Yes, it looks like U5, U6, Q10, Q11 and the associated components are
> > behaving as they should.
> >
> > It certainly could be that D16 and D17 are not either open or shorted,
> > but are not fully functioning as they should. The fact that you could
> > only get the resistance measured at the wiper of R26 as high as 30k does
> > confirm that -- replace the diodes.
> >
> > It also seems from your description that things are a bit intermittent
> > and erratic, so while you are in there to replace the diodes, give the
> > soldering in the wattmeter area (particularly T4) a good inspection and
> > perhaps re-flow the solder with a hot iron (800 degF for the KPA100
> > board), and perhaps add a tiny bit of new solder (actually you are
> > adding a bit of flux).
> >
> > Yes, those diodes are sensitive to lightning surges. Switch the K2
> > antenna to a dummy load when not in use for best results.
> >
> > 73,
> > Don W3FPR
> >
> > On 6/11/2011 4:42 PM, david wrote:
> > > K2/100 s/n 7006
> > > Initial symptom: No control of output power at any knob setting. At
> > > 1-9W setting, output was>10W as measured by external wattmeter, SWR
> > > read back>9.9 (external meter shows around 1:1). At 10-100W setting,
> > > output>100W, SWR>9.9. HI REFL message displayed.
> > >
> > > Unit was previously working fine for several months.
> > >
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