Hi Don, No problem on the delay. OK, after removing 1 turn from T5, the freq. at TP1 (at 4000) is now 8535.14, so it did come up from the previous value, but clearly not enough. I have 4.19 V on pin 5 of U6 and I have 4.21 V on pin 13 of U4.
I wasn't sure of your schedule so I also put in a support request to Elecraft but have not received a reply as of yet. Hopefully between your help and their help I can get this resolved. 73 de John, WB4GLJ On Tue, Apr 30, 2019 at 2:48 PM Don Wilhelm <donw...@embarqmail.com> wrote: > John, > > Where did the TP1 frequency go after you removed a turn? > > It is possible that the VFO frequency is not getting back to U4 pin 4 -- > the signal goes from U3 pin 6 thru C62 and then to U4. > > Did we verify that U6 pin 5 is near 4 volts? What is the voltage at U4 > pin 13? > > Sorry to go over things, but I just returned from a few days away and my > memory is not yet focused. > > 73,, > Don W3FPR > > On 4/28/2019 6:00 PM, John Wingard wrote: > > Don, > > > > Finally got back to the K2 this afternoon. I have confirmed that T5 is > > on the yellow core, with 16 turns through the center on the red and 4 > > turns on the green. I mentioned earlier that I got all the toroids > > from the Toroid Guy, so I felt confident that it was correctly wound. > > I checked all the relay pins on K13, K14, and K15 and did not see any > > solder bridges on any of them. Next, I pulled T5 and removed one turn > > and re-installed. Unfortunately, nothing has changed. I'm still > > getting that same 8.37 V at R30. Incidentally, I'm getting the 8.37 V > > on either side of R30. Is that normal? I can also pull T5 and wind a > > new one with the parts that came with the kit if you think that might > > help, but something tells me that the problem lies elsewhere. I also > > thought about pulling C72 and replacing it with another one, but > > unfortunately there was only one of that value in the kit and I don't > > have anything like it it my parts stash. Any new thoughts? > > > > de John, WB4GLJ > > > > > > > > On Sat, Apr 27, 2019 at 6:00 PM Don Wilhelm <donw...@embarqmail.com > > <mailto:donw...@embarqmail.com>> wrote: > > > > John, > > > > Both frequencies are too low. > > You have either too much capacitance or too much inductance in the > > VFO. > > Count the number of times the red wire goes through the center of > > the T5 > > core - it should be 16. > > > > Check relays K13, K14 and K15 for solder bridges. > > > > Make sure the core of T5 is yellow. > > You might have to try removing a turn from T5 if you can find no > > other > > cause - there have been a few K2s in the long past where the > > permeability if the T5 core was higher than expected, and removing 1 > > turn from T5 corrected things - I have not seen that recently, but > > I do > > mention it 'just in case'. > > > > If all else fails, you may have to "wind your way" through the relay > > connections for the VFO Range Select area using the Relay Table on > > the > > Schematic Key page as your guide for the paths through the relays. > > > > 73, > > Don W3FPR > > > > On 4/27/2019 5:37 PM, John Wingard wrote: > > > Hi Don, > > > > > > Thanks for the quick response. I did check C72 again. It is a 271 > > > value. I then spread the red turns on T5 as far as I could. I'd say > > > they cover about 90+% of the toroid. I put the L30 slug at > > mid-point > > > of travel and measured voltage at R30 and it is still right at 8.37 > > > V. While there I checked the frequency at TP1 and it was 8247.90, > > > which is considerably lower than the 8913 that you expected. > > > > > > Next I went up to 7100 and measured the voltage at R30. Still > > right at > > > 8.37 V, no change. Frequency at TP1 @ 7100 was 11558.11. > > > > > > So, it appears that the frequency at 4000 is not within the > > expected > > > range, and likely not at 7100 as well. Hope this tells you > > something > > > because I'm stumped. > > > I've got some plans for this evening so I may not get back on it > > until > > > tomorrow afternoon, but if you've got any more things for me to > > try I > > > will do them then. > > > > > > John, WB4GLJ > > > > > > On Sat, Apr 27, 2019 at 1:57 PM Don Wilhelm > > <donw...@embarqmail.com <mailto:donw...@embarqmail.com> > > > <mailto:donw...@embarqmail.com <mailto:donw...@embarqmail.com>>> > > wrote: > > > > > > John, > > > > > > That high voltage is trying to reduce the capacity of the > > varactors. > > > Which means there is either too much capacity or too much > > > inductance in > > > the circuit. > > > > > > Check the value of C72 first - it should be marked "271". > > Then set > > > the > > > L30 slug to about mid-position and spread the red turns of T5 > > > enough so > > > the starting and ending turns are adjacent. What is the > > voltage when > > > tuned to 4000 kHz? Measure the frequency at TP1 - it should > > be near > > > 8913 kHz. > > > > > > Then change to 40 meters - 7100 kHz - What is the R30 > > voltage and > > > what > > > is the VFO frequency measured at TP1. > > > > > > The answer to those questions will help in determining what > > to do > > > next. > > > > > > 73, > > > Don W3FPR > > > > > > On 4/27/2019 1:32 PM, John Wingard wrote: > > > > Working on my 2nd K2 (S/N 7869) and have run into a > > problem with > > > the VCO > > > > alignment. I'm getting a constant 8.37 V at R30 at 4.000 > MHz.. > > > I cannot > > > > change it with the full range of L30. Correct type inductor > is > > > installed at > > > > L30. Dropping the VFO down to 3.500 doesn't change it > > either. I > > > have gone > > > > back through the archives and read just about every post > > > concerning this > > > > problem but nothing I have tried has made any difference. > > I have > > > double > > > > checked all correct parts placements and orientations, > > re-flowed all > > > > connections in the quadrant of the board around the VCO > > section. > > > T5 is > > > > wound as per the manual (from the Toroid Guy) and installed > > > correctly. I > > > > have tried both spreading and compressing the turns on T5 > with > > > no change > > > > either way. > > > > > > > > Regarding the thermistor board, I have 4.18 V on pin 5 of > U6. > > > > > > > > Test in the previous section were within specs: > > > > > > > > 4 MHz Oscillator Cal using CAL FCTR was 12099.61 and > confirmed > > > with an > > > > external counter. > > > > Range of the PLL reference oscillator: 12099.61 - 12086.01 = > > > 13.59 kHz > > > > VCO oscillator test: 8162.60 MHz > > > > > > > > I'm about out of ideas at this point. What should I start > > > checking next? > > > > > > > > Thanks for any help! > > > > > > > > 73 de John, WB4GLJ > > > > > ______________________________________________________________ > > > > Elecraft mailing list > > > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > > > Help: http://mailman.qth.net/mmfaq.htm > > > > Post: mailto:Elecraft@mailman.qth.net > > <mailto:Elecraft@mailman.qth.net> > > > <mailto:Elecraft@mailman.qth.net > > <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
