Tedd, Yes, a low BFO voltage would cause poor receive sensitivity. I doubt that pulling the crystals caused the problem, but the new crystals may fix it. While you are removing things, you may want to arbitrarily replace the NE612 at U6 just in case.
I recently repaired a K2 with a similar problem with one of the K2s I built last May - I can't say just what the problem was (most likely the crystals), but this one had failed before and replacing the NE612 appeared to correct it the first time, but after having a similar failure a second time, I replaced the crystals, varactors, inductor and the NE612 - I do hope and trust that it will stay fixed now (no, this was not a solder connection problem). 73, Don W3FPR > -----Original Message----- > > First some history. During the BFO test, I discovered my BFO > range was low. My upper frequency was 4917.55 and lower > frequency was 4914.26. After much consultation with Gary, I > tried the various tricks such as padding C174 and C173, adding > caps to the junction of X3 and X4, and even adding turns to L33. > After much prodding I finally got the range from 4917.55 to > 4912.60. So far so good. I also got my filters aligned with > Spectrogram which proved to be very easy. Then I noticed my > receiver sensitivity appeared to be very low. (Even worse than > my ICOM 706. Now that's bad!) Out came the XG2 to perform some > MDS tests. Following the directions from the XG2 manual for > setting up the K2, inputting 1 uV, and with the AF gain at > maximum, I measure .009 volts at the speaker terminals. With no > input I can't even get a reading. (Kinda hard to divide by > zero.) This led me to the signal tracing portion on the manual. > I got as far as the BFO output measurement and there I r! > an into the problem of a very low BFO output to U6 pin 1. The > manual states .20 to .70 Vrms and I get .05 Vrms with my RF > probe. Could my super stiff crystals be the cause of such low > output? Perhaps I tried bending the crystals too much? Would a > low BFO output cause such low receiver sensitivity? Are there > some other components to suspect other than the crystals? > Incidently Elecraft is sending me another set of BFO crystals, > gratis, to hopefully cure my BFO range problem without padding. > Thanks for reading. Merry Christmas and Happy New Year to all > Elecrafters. > > Tedd K6OI > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
