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 <[email protected]> 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 <[email protected] > > <mailto:[email protected]>> 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:[email protected] > > <mailto:[email protected]> > > > > > > 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
