I forgot to mention that all testing is into a known good DL1 dummy load that I’m also using for my external power readings.
Any wise insights are most welcome! Steve - KY7K k...@arrl.net Get OUT and play radio! On Oct 4, 2014, at 10:28 PM, KY7K <k...@cox.net> wrote: > I recently purchased a used K2 (Rev A) from a club that was not working > because it had been “hooked up backward”. That is the best anyone can > remember as to what happened to the radio ~7 years ago… > > Currently, the power output as displayed on the radio and on an external > power meter is very unstable and does not match the power setting desired. > This is not just a little off, I can select 1W on the radio and then hit the > tune button 5 times and might get .4W, 6.7W, HI-CUR, 9.0W, 1.2W. > This is the QRP K2 with SSB, NB, KIO2 and DSP options. The problem occurs > with or without the option boards installed. > > Background: > When I first tested it, it would power on but the only function that was > operational was the power control. Every other knob and button was > non-functioning as if the cpu was hung up. The radio was not transmitting in > this state. > I had a old CPU (U6) from my other K2 that I installed as a test and that > seemed to fix the problem, at least in receive. I, unfortunately, did not > test it in transmit. > I ordered a FWK2MCIO kit to get a new cpu and also ordered all the mod kits > for the Rev A to Rev B upgrade, once they came in I installed everything and > while performing the the calibrations after the upgrade discovered that the > transmit power was very unstable between transmissions. > Other than the bad U6, the only other issue I found was that the PCB trace > from pin 5 of the Mic connector on the front panel board was basically > missing, from getting shorted to +12V I assume, it disintegrated when > touched... > > I’ve narrowed the issue down to the control board, since if I swap the > control board from my working K2 into the bad radio the power issue > disappears. > I’ve checked VRFDET, VALC, and VPWR on the control board and they are all OK > best I can tell, and I’m now at a loss where to look next. > Note: the power level is stable once it settles on some random output power. > The power level is random from one transmission to the next. > > The following links are images showing a tune cycle. > The first image shows the full scan with the radio set to ~1W and actually > putting out ~.4W. The second image is zoomed in on the start of the cycle. > https://www.dropbox.com/s/i64sw2ue2405roe/k2_0_5w_full.png?dl=0 > https://www.dropbox.com/s/qe297am756igbd4/k2_0_5w_zoom.png?dl=0 > > This is with the power set to ~7W and the radio indicating hi-cur, before > settling down to ~6.4W > https://www.dropbox.com/s/tqxzi3yk13gye4g/k2_hicur_full.png?dl=0 > https://www.dropbox.com/s/6qz10478zt66tjd/k2_hicur_zoom.png?dl=0 > > > > Steve - KY7K > k...@arrl.net > Get OUT and play radio! > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to k...@cox.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
