Re: [Elecraft] K2 BFO problem
Snowy, I am glad to hear that it is now working for you. It sounds like you had a soldering problem somewhere. A surplus of solder usually means that the lead and solder pad were not heated sufficiently. If you have other areas where you find excess solder, just reheat and if necessary, wick away the excess - you may have a fully functional K2 sooner than you think. It sounds as though some (or perhaps all) of the K2 A to B mods were installed in an attempt to get it working. Which of the group of mods is installed is important to keeping track of the level of the K2. You may want to download the K2ATOB instructions and all the other mod instructions to do a physical check of the installed components. Knowing the level of mods installed is important when chasing problems. Make a log of the A to B mods installed for future reference. The level of the IF crystals on the RF board and the KSB2 option is also important to having a good filter response - those crystals should be marked with a "-S" suffix.K2s above SN 2560 have the new crystals. If the wiring mod for the sidetone source with firmware 2.04 has not been installed, do it. It is required for the KIO2 or the KPA100 (see the instructions for those options) . If you have MCU 2.04r firmware it is mandatory - you will not have sidetone without it. If your firmware is 2.04P or earlier set the menu sidetone to U4-8. 73 - Merry Christmas and Happy New Year, Don W3FPR On 12/19/2021 5:36 PM, snowy howell via Elecraft wrote: Good Evening Don Sorry for the late reply, not used to the format of > the reflector and stumbled onto your suggestions to solve my BFO > problem. I am please to say that I have now got it working > correctly. Getting nowhere with the test I decided to dismantle the > radio down to just the RF board, removed a surplus of solder from the > D36/37 area, re-flowed the pins of U10, lifted the leg of the 5.1meg > resistor and L33, didn’t know about the rubber bung being conductive > however once again removed a surplus of solder from that area, I also > added a small cut of insulation tape to form a bed for the resistor > on L33, thinking that turns may be shorted, at this point I ought to > explain I purchased this as a built but non worker, it is an early > radio as it has a Rev A mother-board with a small pot for R60 and an > early control board with the 12v switch rather than the berg > connectors, I have built 5 or 6 of these for people and never had a > problem certainly not as many faults as this one appears to have had, > there is no serial number on the radio, but it has had the PLL > thermistor conversion as well as the D36 done. Have to thank Dave for > sticking with me on this one, without his guidance I would still be > trying to sort the PLL problem. > > Have a good Christmas and New Year 2022 > > 73 > > Snowy G0HZE > > Sent from Mail for Windows > > __ > 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 Message delivered to > d...@w3fpr.com ere __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2 BFO problem
Good Evening Don Sorry for the late reply, not used to the format of the reflector and stumbled onto your suggestions to solve my BFO problem. I am please to say that I have now got it working correctly. Getting nowhere with the test I decided to dismantle the radio down to just the RF board, removed a surplus of solder from the D36/37 area, re-flowed the pins of U10, lifted the leg of the 5.1meg resistor and L33, didn’t know about the rubber bung being conductive however once again removed a surplus of solder from that area, I also added a small cut of insulation tape to form a bed for the resistor on L33, thinking that turns may be shorted, at this point I ought to explain I purchased this as a built but non worker, it is an early radio as it has a Rev A mother-board with a small pot for R60 and an early control board with the 12v switch rather than the berg connectors, I have built 5 or 6 of these for people and never had a problem certainly not as many faults as this one appears to have had, there is no serial number on the radio, but it has had the PLL thermistor conversion as well as the D36 done. Have to thank Dave for sticking with me on this one, without his guidance I would still be trying to sort the PLL problem. Have a good Christmas and New Year 2022 73 Snowy G0HZE Sent from Mail for Windows __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2 BFO problem
Snowy, It sounds as though you have the proper BFO crystals installed at X3 and X4. Do check the values of C173 and C174 first Then check L33 to make certain it is well soldered and the leads are attached to the 1/8 watt resistor leads. Check D37 and D38 to be certain they are oriented properly and well soldered. Lastly, lift one side of L33 (and its resistor and remove the rubber pad - check the resistance of the pad itself - there were a few (a while ago) that were found to be conductive causing problems such as yours. Since you did not state the vintage (or serial number of the K2), do that check if those items above do not correct the problem. While you have the rubber pad out, make certain that about 1/2 of the stem has been cut away. That is to allow the 1/8 watt resistor to be pushed down into the center of L33 to tighten the leads and hold L33 securely in place. If the rubber pad under L33 is found to be conductive, get a new one from Elecraft, or -- If you have an unassembled KAT2, you will find several of the rubber bumpers in that kit - a conductive one will work fine in the KAT2, but not in the BFO circuit. 73, Don W3FPR On 12/16/2021 5:35 PM, ROLAND HOWELL via Elecraft wrote: having repaired my PLL problem with a great deal of help and advice from Dave at tech support, Elecraft i moved onto the next set of tests which was the bfo frequencies, on selecting CAL, Counter i get a reading of 4.9136, on pressing either the band up or down all i get is zero's. Fitted crystals are 4.91s in X3 and X4 positions Have checked all the details in the trouble shooting paragraph, i can find no fault with any of the components, all values and positions are correct. I have to add that this was purchased as a non-runner. Any advice appreciated Snowy,G0HZE __ 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 Message delivered to d...@w3fpr.com __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2 BFO problem, need JFET advice
Tyler, Since you have low audio output during receive, I would suggest you are looking in the wrong place. Q24 is not involved during receive, and will show no signal at TP2 during receive. The 400 mV at the gate of Q24 is just fine. Put the K2 menu into CAL FCTR and then check the RF level at TP2 - it should be somewhere between 25 and 70 millivolts. You may be in for some Signal Tracing. Use the steps found in Appendix E of the manual. On 7/1/2011 10:45 AM, Tyler Barnett wrote: Symptom: K2 with very low audio output, only the strongest stations can be copied. Have eliminated the BPF, attenuator, pre-amp, and so forth with signal tracing. Transmit stops increasing at about 4W, the control runs out of effect. So the K2 is alive, but something is wrong in the signal path. The BFO area was redone with a mod (which I have no paperwork on, somebody else's radio). The components were dead-bugged onto the area around the T33 BFO toroid, and I believe they shorted out on the bottom cover. Using the included kit RF probe, test point TP2 has only 1 millivolt on it, but Q24 has about 0.4Vrms on the gate, which is fed from U11 pin 6 and through the BFO components. Thus, it appears to be a blown Q24, which is a JFET J310. Radio Shack has a MPF102, would that be OK to use? I've checked the respective datasheets of J310 vs MPF102, and I haven't found much difference in ratings, even the noise figure is about the same. Your comments appreciated ASAP! __ 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
Re: [Elecraft] K2 BFO problem
You were right, Don, as usual. The problem was an unsoldered point on the control board. I was looking on the wrong board the whole time. All tests and adjustments on Part II are complete and I'm moving forward. Thanks for all the help! Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Monday, July 19, 2010 9:06 AM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, You are likely chasing a bad solder connection - things that change by themselves is usually an indication of a solder problem. You are getting close if it was the Q24 drain voltage changing. Check RF Board R98, and then go to the Control Board and check the components shown on the Control Board schematic area marked ALC (at the top of the page). Double-check the position of the components soldered on the back of the board. When in CAL FCTR, tapping BAND+ should result in a high voltage on the VALC line, and tapping BAND-, it should drop to zero. Don't forget to check the connectors between the Control Board and the RF Board. 73, Don W3FPR __ 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
Re: [Elecraft] K2 BFO problem
Ken, You are likely chasing a bad solder connection - things that change by themselves is usually an indication of a solder problem. You are getting close if it was the Q24 drain voltage changing. Check RF Board R98, and then go to the Control Board and check the components shown on the Control Board schematic area marked ALC (at the top of the page). Double-check the position of the components soldered on the back of the board. When in CAL FCTR, tapping BAND+ should result in a high voltage on the VALC line, and tapping BAND-, it should drop to zero. Don't forget to check the connectors between the Control Board and the RF Board. 73, Don W3FPR Ken Mohler wrote: Don - It gets weirder and weirder. I did the test of the Q24 drain voltage. When I tapped Band+ I got 3.4V. BAND- dropped to a little less than a volt. Then I went on to check the following things you suggested. Now here's where it got weird... I went back to redo the Q24 drain voltage and now I get around 0 volts no matter which BAND button I tap. I didn't change anything - honest! I'm less convinced that the problem lies within Q24. Perhaps Q24 is not getting the right signals from the other side. My first K2 went together with nary a glitch, and I have been even more deliberate and careful with this one. If you still have the patience, suggest what I ought to do next. 73, Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Saturday, July 17, 2010 7:57 PM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, The fuzzy waveform on the 'scope is normal - but how much so is difficult for me to say whether yours is normal or abnormal. Check the value of C169 - it should be 390 pF (marked 391). OK, the BFO is oscillating, so look at Q24 carefully - is it oriented correctly? If so, enter CAL FCTR and tap the BAND+ button while measuring the voltage on the drain (see the schemastic key page if you are not familiar with the pinout). The voltage should go high(almost 8 volts), and then tap BAND- and the voltage should go nearly to zero. Other things to check - look for a solder bridge between pins 1 and 2 of U10;, check the SMT1B for correct orientation; re-check the orientation of D36, and check the soldering of R98, C168, D36, R99 and SMT1B. If all the above is correct, try replacing Q24. If you have a J309 around, try that (if you have the KDSP2 kit, there are J309s in there). 73, Don W3FPR Ken Mohler wrote: Don - You have me on the right track. I have a valid frequency reading at pin 6 of U11 and I can follow it back through L33 and C169 to the gate of Q24. The waveform gets fuzzier and has lower amplitude past L33 (I do have a scope) but is still countable at C169. Past Q24 I don't have anything recognizable. I have reflowed the solder on everything around there. D36 appears to be installed correctly. I don't have an extra J310 to swap out Q24, but will get one if you think that's the next step. BTW, I measured the voltages at U11 and all are what you told me to expect except pin 8 is around 6 volts. Still, the BFO seems to be working, just not getting anything as far as TP2. Thanks for the help and please keep it coming. 73, Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Friday, July 16, 2010 6:49 PM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, Did you obtain a good frequency reading when you did the PLL Reference Oscillator test back on page 36? If so, check the probe again by putting the probe into either TP3 or TP1. If you see a valid frequency displayed, your probe is OK. The most common problem builders have are soldering problems. Re-flow the soldering in the BFO and U11 area with a hot soldering iron (750 deg/F). Also check carefully for solder bridges. Unfortunately, one lead of both X3 and X4 are under the pad for L33, so ignore those for the time being (if nothing else works, Lift one end of the resistor securing L33 and re-flow the soldering at those leads). Do you have near 8 volts at U11 pin 8? Is U11 pin 1 and 2 close to 1.4 volts? Do you have about 6 volts at U11 pin 6? Touch the counter probe to U11 pin 6 (careful not to short to an adjacent pin). Do you have a valid frequency reading? If you do, then the BFO is working, and the problem is with Q24 and its associated components. Be certain you have mounted D36 (the SMT1B) part correctly, and the soldering of Q24, RP6, R98, and R99 is good. If still no progress, either assemble the parts provided in your K2 kit for the RF Probe (schematic in Appendix E) or let us know that you have an oscilloscope available. 73, Don W3FPR Ken Mohler wrote: Hi Gang - I'm building my 2nd K2 and am at the point of Alignment and Test, Part
Re: [Elecraft] K2 BFO problem
Don - It gets weirder and weirder. I did the test of the Q24 drain voltage. When I tapped Band+ I got 3.4V. BAND- dropped to a little less than a volt. Then I went on to check the following things you suggested. Now here's where it got weird... I went back to redo the Q24 drain voltage and now I get around 0 volts no matter which BAND button I tap. I didn't change anything - honest! I'm less convinced that the problem lies within Q24. Perhaps Q24 is not getting the right signals from the other side. My first K2 went together with nary a glitch, and I have been even more deliberate and careful with this one. If you still have the patience, suggest what I ought to do next. 73, Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Saturday, July 17, 2010 7:57 PM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, The fuzzy waveform on the 'scope is normal - but how much so is difficult for me to say whether yours is normal or abnormal. Check the value of C169 - it should be 390 pF (marked 391). OK, the BFO is oscillating, so look at Q24 carefully - is it oriented correctly? If so, enter CAL FCTR and tap the BAND+ button while measuring the voltage on the drain (see the schemastic key page if you are not familiar with the pinout). The voltage should go high(almost 8 volts), and then tap BAND- and the voltage should go nearly to zero. Other things to check - look for a solder bridge between pins 1 and 2 of U10;, check the SMT1B for correct orientation; re-check the orientation of D36, and check the soldering of R98, C168, D36, R99 and SMT1B. If all the above is correct, try replacing Q24. If you have a J309 around, try that (if you have the KDSP2 kit, there are J309s in there). 73, Don W3FPR Ken Mohler wrote: Don - You have me on the right track. I have a valid frequency reading at pin 6 of U11 and I can follow it back through L33 and C169 to the gate of Q24. The waveform gets fuzzier and has lower amplitude past L33 (I do have a scope) but is still countable at C169. Past Q24 I don't have anything recognizable. I have reflowed the solder on everything around there. D36 appears to be installed correctly. I don't have an extra J310 to swap out Q24, but will get one if you think that's the next step. BTW, I measured the voltages at U11 and all are what you told me to expect except pin 8 is around 6 volts. Still, the BFO seems to be working, just not getting anything as far as TP2. Thanks for the help and please keep it coming. 73, Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Friday, July 16, 2010 6:49 PM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, Did you obtain a good frequency reading when you did the PLL Reference Oscillator test back on page 36? If so, check the probe again by putting the probe into either TP3 or TP1. If you see a valid frequency displayed, your probe is OK. The most common problem builders have are soldering problems. Re-flow the soldering in the BFO and U11 area with a hot soldering iron (750 deg/F). Also check carefully for solder bridges. Unfortunately, one lead of both X3 and X4 are under the pad for L33, so ignore those for the time being (if nothing else works, Lift one end of the resistor securing L33 and re-flow the soldering at those leads). Do you have near 8 volts at U11 pin 8? Is U11 pin 1 and 2 close to 1.4 volts? Do you have about 6 volts at U11 pin 6? Touch the counter probe to U11 pin 6 (careful not to short to an adjacent pin). Do you have a valid frequency reading? If you do, then the BFO is working, and the problem is with Q24 and its associated components. Be certain you have mounted D36 (the SMT1B) part correctly, and the soldering of Q24, RP6, R98, and R99 is good. If still no progress, either assemble the parts provided in your K2 kit for the RF Probe (schematic in Appendix E) or let us know that you have an oscilloscope available. 73, Don W3FPR Ken Mohler wrote: Hi Gang - I'm building my 2nd K2 and am at the point of Alignment and Test, Part II. All of the tests and alignment steps through the VCO alignment have been completed successfully. Everything has been right in the center of the expected parameters. Then I got to the BFO test. I'm getting a reading of .00. Here's what I know so far: D37 and D38 are the correct types and oriented properly. I have measured the resistance across the resistor holding L33 down (or up?) and get a reading of 1.5 ohms, indicating to me that L33 is intact and effectively soldered to the resistor leads. I have checked the positioning of Q24 and it looks correct. The right crystals are installed at X3 and X4 and grounding the cases went smoothly, so I don't think I overheated them. I have
Re: [Elecraft] K2 BFO problem
Ken, Make sure you have your probe plugged into the correct jack. Sounds like what first happened to me, until I turned the rig around (back to me) I forgot there were 2 jacks. Probably not the problem, but hey, you never know. John K2QY __ 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
Re: [Elecraft] K2 BFO problem
Don - You have me on the right track. I have a valid frequency reading at pin 6 of U11 and I can follow it back through L33 and C169 to the gate of Q24. The waveform gets fuzzier and has lower amplitude past L33 (I do have a scope) but is still countable at C169. Past Q24 I don't have anything recognizable. I have reflowed the solder on everything around there. D36 appears to be installed correctly. I don't have an extra J310 to swap out Q24, but will get one if you think that's the next step. BTW, I measured the voltages at U11 and all are what you told me to expect except pin 8 is around 6 volts. Still, the BFO seems to be working, just not getting anything as far as TP2. Thanks for the help and please keep it coming. 73, Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Friday, July 16, 2010 6:49 PM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, Did you obtain a good frequency reading when you did the PLL Reference Oscillator test back on page 36? If so, check the probe again by putting the probe into either TP3 or TP1. If you see a valid frequency displayed, your probe is OK. The most common problem builders have are soldering problems. Re-flow the soldering in the BFO and U11 area with a hot soldering iron (750 deg/F). Also check carefully for solder bridges. Unfortunately, one lead of both X3 and X4 are under the pad for L33, so ignore those for the time being (if nothing else works, Lift one end of the resistor securing L33 and re-flow the soldering at those leads). Do you have near 8 volts at U11 pin 8? Is U11 pin 1 and 2 close to 1.4 volts? Do you have about 6 volts at U11 pin 6? Touch the counter probe to U11 pin 6 (careful not to short to an adjacent pin). Do you have a valid frequency reading? If you do, then the BFO is working, and the problem is with Q24 and its associated components. Be certain you have mounted D36 (the SMT1B) part correctly, and the soldering of Q24, RP6, R98, and R99 is good. If still no progress, either assemble the parts provided in your K2 kit for the RF Probe (schematic in Appendix E) or let us know that you have an oscilloscope available. 73, Don W3FPR Ken Mohler wrote: Hi Gang - I'm building my 2nd K2 and am at the point of Alignment and Test, Part II. All of the tests and alignment steps through the VCO alignment have been completed successfully. Everything has been right in the center of the expected parameters. Then I got to the BFO test. I'm getting a reading of .00. Here's what I know so far: D37 and D38 are the correct types and oriented properly. I have measured the resistance across the resistor holding L33 down (or up?) and get a reading of 1.5 ohms, indicating to me that L33 is intact and effectively soldered to the resistor leads. I have checked the positioning of Q24 and it looks correct. The right crystals are installed at X3 and X4 and grounding the cases went smoothly, so I don't think I overheated them. I have reflowed the solder on the parts around the BFO area. A symptom that may or may not mean anything: the S-Meter is showing S5. It was properly adjusted back in Alignment and Testing Part I. What should I do next? __ 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
Re: [Elecraft] K2 BFO problem
Ken, The fuzzy waveform on the 'scope is normal - but how much so is difficult for me to say whether yours is normal or abnormal. Check the value of C169 - it should be 390 pF (marked 391). OK, the BFO is oscillating, so look at Q24 carefully - is it oriented correctly? If so, enter CAL FCTR and tap the BAND+ button while measuring the voltage on the drain (see the schemastic key page if you are not familiar with the pinout). The voltage should go high(almost 8 volts), and then tap BAND- and the voltage should go nearly to zero. Other things to check - look for a solder bridge between pins 1 and 2 of U10;, check the SMT1B for correct orientation; re-check the orientation of D36, and check the soldering of R98, C168, D36, R99 and SMT1B. If all the above is correct, try replacing Q24. If you have a J309 around, try that (if you have the KDSP2 kit, there are J309s in there). 73, Don W3FPR Ken Mohler wrote: Don - You have me on the right track. I have a valid frequency reading at pin 6 of U11 and I can follow it back through L33 and C169 to the gate of Q24. The waveform gets fuzzier and has lower amplitude past L33 (I do have a scope) but is still countable at C169. Past Q24 I don't have anything recognizable. I have reflowed the solder on everything around there. D36 appears to be installed correctly. I don't have an extra J310 to swap out Q24, but will get one if you think that's the next step. BTW, I measured the voltages at U11 and all are what you told me to expect except pin 8 is around 6 volts. Still, the BFO seems to be working, just not getting anything as far as TP2. Thanks for the help and please keep it coming. 73, Ken K0WKM -Original Message- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Friday, July 16, 2010 6:49 PM To: Ken Mohler Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 BFO problem Ken, Did you obtain a good frequency reading when you did the PLL Reference Oscillator test back on page 36? If so, check the probe again by putting the probe into either TP3 or TP1. If you see a valid frequency displayed, your probe is OK. The most common problem builders have are soldering problems. Re-flow the soldering in the BFO and U11 area with a hot soldering iron (750 deg/F). Also check carefully for solder bridges. Unfortunately, one lead of both X3 and X4 are under the pad for L33, so ignore those for the time being (if nothing else works, Lift one end of the resistor securing L33 and re-flow the soldering at those leads). Do you have near 8 volts at U11 pin 8? Is U11 pin 1 and 2 close to 1.4 volts? Do you have about 6 volts at U11 pin 6? Touch the counter probe to U11 pin 6 (careful not to short to an adjacent pin). Do you have a valid frequency reading? If you do, then the BFO is working, and the problem is with Q24 and its associated components. Be certain you have mounted D36 (the SMT1B) part correctly, and the soldering of Q24, RP6, R98, and R99 is good. If still no progress, either assemble the parts provided in your K2 kit for the RF Probe (schematic in Appendix E) or let us know that you have an oscilloscope available. 73, Don W3FPR Ken Mohler wrote: Hi Gang - I'm building my 2nd K2 and am at the point of Alignment and Test, Part II. All of the tests and alignment steps through the VCO alignment have been completed successfully. Everything has been right in the center of the expected parameters. Then I got to the BFO test. I'm getting a reading of .00. Here's what I know so far: D37 and D38 are the correct types and oriented properly. I have measured the resistance across the resistor holding L33 down (or up?) and get a reading of 1.5 ohms, indicating to me that L33 is intact and effectively soldered to the resistor leads. I have checked the positioning of Q24 and it looks correct. The right crystals are installed at X3 and X4 and grounding the cases went smoothly, so I don't think I overheated them. I have reflowed the solder on the parts around the BFO area. A symptom that may or may not mean anything: the S-Meter is showing S5. It was properly adjusted back in Alignment and Testing Part I. What should I do next? __ 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
Re: [Elecraft] K2 BFO problem
Ken, Did you obtain a good frequency reading when you did the PLL Reference Oscillator test back on page 36? If so, check the probe again by putting the probe into either TP3 or TP1. If you see a valid frequency displayed, your probe is OK. The most common problem builders have are soldering problems. Re-flow the soldering in the BFO and U11 area with a hot soldering iron (750 deg/F). Also check carefully for solder bridges. Unfortunately, one lead of both X3 and X4 are under the pad for L33, so ignore those for the time being (if nothing else works, Lift one end of the resistor securing L33 and re-flow the soldering at those leads). Do you have near 8 volts at U11 pin 8? Is U11 pin 1 and 2 close to 1.4 volts? Do you have about 6 volts at U11 pin 6? Touch the counter probe to U11 pin 6 (careful not to short to an adjacent pin). Do you have a valid frequency reading? If you do, then the BFO is working, and the problem is with Q24 and its associated components. Be certain you have mounted D36 (the SMT1B) part correctly, and the soldering of Q24, RP6, R98, and R99 is good. If still no progress, either assemble the parts provided in your K2 kit for the RF Probe (schematic in Appendix E) or let us know that you have an oscilloscope available. 73, Don W3FPR Ken Mohler wrote: Hi Gang - I'm building my 2nd K2 and am at the point of Alignment and Test, Part II. All of the tests and alignment steps through the VCO alignment have been completed successfully. Everything has been right in the center of the expected parameters. Then I got to the BFO test. I'm getting a reading of .00. Here's what I know so far: D37 and D38 are the correct types and oriented properly. I have measured the resistance across the resistor holding L33 down (or up?) and get a reading of 1.5 ohms, indicating to me that L33 is intact and effectively soldered to the resistor leads. I have checked the positioning of Q24 and it looks correct. The right crystals are installed at X3 and X4 and grounding the cases went smoothly, so I don't think I overheated them. I have reflowed the solder on the parts around the BFO area. A symptom that may or may not mean anything: the S-Meter is showing S5. It was properly adjusted back in Alignment and Testing Part I. What should I do next? __ 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
Re: [Elecraft] K2 BFO problem - need suggestions
Jim, That behavior is indicative of a bad solder connection. The main components in the BFO area are X3 and X4, C173 and C174, D37 and D38, L33, and RP6. The path to the TP2 BFO counter probe also includes Q24, C169, R98 and C168, but since the problem seems to be frequency oriented, I would suggest that the last list is only of secondary concern.. On a 4 year old K2, I believe you have the yellow core toroid at L33. You may do well to upgrade with the BFOMDKT which will provide an extra degree of temperature stability for the BFO. If you have the L33 toroid wound with #36 wire (many turns, comes pre-wound), then you already have that mod installed. It is also possible that you have a bad BFO crystal, but check out the other possibilities before reaching that conclusion. Of course, if you have to order parts from Elecraft, it is probably more economical to just order the BFO crystals at the same time whether they are needed or not. 73, Don W3FPR Elmore's wrote: Greetings everyone, I have a 4+ year old K2 which has provided spotless service for me until recently. I began to have an audio issue in that on power up I would not have audio. I could get it back intermittently by either powering down and back up or by switching through the modes. In doing some basic troubleshooting I discovered that by touching the L33 coil in the BFO I would have audio again. While checking the BFO frequency using the internal frequency counter I discovered that when I did not have audio the frequency was reading either 4.5 or 5.5 Mhz depending on the sideband selected. After regaining audio the frequency would be back at 4.9 MHz. Thus, it appears the oscillator is oscillating but at an incorrect frequency until I introduce my body capacitance. Can anyone help me in troubleshooting so that I could isolate the component or does anyone know of the most likely cause of such a problem? Thanks fo your help, Jim WA4YWM __ 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
