Hi Don, I’m sure you remember that my K2 kit (serial 7818) experienced the exact same issue. I went through all of your suggestions without any success.
My K2 is now in the hands of Elecraft Support. I’m hoping they will find a solution to my (and John’s) issue. Just a FYI. Many thanks for all of your help! 73 Don, KE0PVQ Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Don Wilhelm<mailto:donw...@embarqmail.com> Sent: Saturday, April 27, 2019 5:01 PM To: John Wingard<mailto:jwin1...@gmail.com> Cc: Elecraft@mailman.qth.net<mailto:Elecraft@mailman.qth.net> Subject: Re: [Elecraft] K2 VCO Alignment Issue 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>> 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> > > > > 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 ______________________________________________________________ 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
