Hi Don, Thank you for your help and information! K15 was the offender - when hot, pins 3 to 4 and also 7 to 8 stay connected after changing the band from 20m down to 40 or 80. This cuts off the path through K14 and K13 to C71 and C72.
73, Phil W6TQG > -----Original Message----- > From: Don Wilhelm [mailto:w3...@embarqmail.com] > Sent: Wednesday, June 02, 2010 5:50 PM > To: Phil-W6TQG > Cc: elecraft@mailman.qth.net > Subject: Re: [Elecraft] K2/100 Has No Output on 80 or 40 When Hot > > Phil, > > The problem will be found in the VFO Range Selection area. > Look at the > schematic for the RF Board sheet 1. > Check the soldering of C71 and C72 and relay K13. > It is possible that when hot, the contacts of K13 (and > possibly K14) are > not making good contact. > Set to 80 meters and wait until the failure occurs, then power the K2 > off and quickly (before things cool), check for continuity > between K13 > pins 3 and 4 also between pins 7 and 8 - both should be zero > ohms - if > not, the relay has failed. > Check K14 in a similar manner, but set to 40 meters - after > the failure, > you should have continuity between pins 3 and 4 of K14 and > also between > pins 7 and 8. > > The relay pins are numbered like an IC (pins 1 and 10 are at the same > end). Look for the round solder pad at pin 1 (or the end > with the white > stripe). > > This is either a temperature related solder connection or a relay > contact problem. > > 73, > Don W3FPR > > Phil-W6TQG wrote: > > Hi Don, > > > > Thank you for your help. Yes, it appears to be the VFO. The > VCO readings > > at TP1 for 20, 30, 40 and 80m are normal when the K2 is > cool, but when > > hot the readings are near 15,600 for 40 and 17,257 for 80. > No wonder I > > can't transmit or receive! 20 and 30m appear to be normal when hot. > > > > What do you suggest I look at next? > > > > 73, > > Phil > > > > > > > >> -----Original Message----- > >> From: Don Wilhelm [mailto:w3...@embarqmail.com] > >> Sent: Tuesday, June 01, 2010 6:08 AM > >> To: Phil-W6TQG > >> Cc: elecraft@mailman.qth.net > >> Subject: Re: [Elecraft] K2/100 Has No Output on 80 or 40 When Hot > >> > >> Phil, > >> > >> To use the base K2 BNC antenna jack, you must remove the > >> KPA100 - if you > >> attempt to use that jack, the load impedance between the base > >> K2 and the > >> KPA100 will not be correct, and "strange happenings" will > be present. > >> > >> A total lack of power (yes, a display of 0.1 or 0.2 watts is > >> actually no > >> power out) is most likely a problem either in the bandpass > >> filter or a > >> problem with the VFO. Try the VFO first - set the frequency > >> to the low > >> end of the band and check the frequency with the counter > probe in TP1 > >> using CAL FCTR - compare your frequency reading with the > chart on the > >> Schematic Key page. If you want to calculate the proper VFO > >> frequency > >> it should be within a few kHz of the frequency on the dial > >> plus 4915 for > >> bands below 15 meters. > >> > >> Check all the components in the bandpass filter area for 40m > >> and for 80 > >> meters. On 40 meters, be certain C6 is properly installed > >> between the > >> two outer holes of the J15 position (the center hole > should be empty). > >> > >> 73, > >> Don W3FPR > >> > >> Phil-W6TQG wrote: > >> > >>> Every since the last Field Day, my K2/100 (#3713) loses > >>> > >> output, and the > >> > >>> receiver goes dead, on 40m and 80m when it gets hot. This > occurs for > >>> power levels of 9 watts and 100 watts. The 30m through 10m > >>> > >> bands are OK. > >> > >>> I can easily replicate the problem when the power amp is > >>> > >> connected, but > >> > >>> so far it seems to be OK when it is completely unplugged > >>> > >> from the K2. > >> > >>> Turning off the power amplifier through the Secondary Menu > >>> > >> does not make > >> > >>> a difference. While transmitting at 9W, the readings on the > >>> > >> display for > >> > >>> 40 and 80 are "0.1 1.01 - 1". With the power amplifier > >>> > >> connected to the > >> > >>> K2, I temporarily connected the antenna to J4 on the K2, so > >>> > >> that I could > >> > >>> bypass the power amplifier path. This did not help the dead > >>> > >> reception on > >> > >>> 40 or 80. I also tried connecting a dummy load through a > >>> > >> power meter to > >> > >>> J4 and transmitting at 9W. Again 40 and 80 didn't work but > >>> > >> the higher > >> > >>> bands were OK. > >>> > >>> I am assuming that the problem is in the LPF of the power > >>> > >> amplifier, but > >> > >>> am not sure 30m is OK, while 40 and 80 are not. Any hints would be > >>> appreciated. > >>> > >>> 73, > >>> Phil W6TQG > >>> > >>> ______________________________________________________________ > >>> 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 > >>> > >>> > >>> > > > > > > > ______________________________________________________________ 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
