Intermittent loss of power output K3
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Intermittent loss of power output K3
 
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Good day
Late last year, my K3 (no 6957) developed a fault. The symptoms were: 1. No power output when keying the rig 2. TX LED on when keyed, (sidetone generated in CW mode) 3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0 - 100 4. ATU tune command: relays clicking, TX LED on, no power output, no indication on SWR meter; two horizontal dashes in the VFO A display area where normally one would see the resolving SWR; in VFO B area 5.0W is indicated 5. TX gain calibration failed on 5W and 50W; mW TX calibration gain OK I contacted Elecraft Support who suspected a failure of the LPA PA transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA board was found to be dead. Q4 and Q5 were replaced, re-biased and tested. On getting the rig back, the same symptoms were present, but lasted only a short while and the rig then performed normally, enough to have a couple of QSOs, but then failed. Since then the same symptoms have been present intermittently. I asked a friend who also has a K3 to try the rig to make sure I was not doing something silly. For about 20 minutes after switch on the symptoms were present, then for no apparent reason the rig performed normally for approximately 10 minutes before failing again. We were testing by repeatedly invoking ATU tune functions on different bands. Since then, the rig will work or not work on switch on; it has worked flawlessly for several hours but sometimes will present only the listed symptoms for several hours after switch on. When it is working, it all works, specifically the TX gain calibration completes normally After several days of performing normally, I relocated the rig to my alternative operating location; it did not work, with the same symptoms. Elecraft Support has been as exemplary as ever, but they are loth for me to return the rig when it may well sit on the test bench being smug and behaving normally. It seems to me that the possibilities are (i) a dry solder joint (ii) a loose connection or (iii) a component on the verge of failing. I think I should next dismantle and reassemble the rig to try to exclude option (ii), and perhaps find either (i) or (iii), although needle and haystack comes to mind... Has anyone suffered similar problems and found a solution, or can someone advise where I should concentrate my search? Peter M0RYB -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Intermittent loss of power output K3
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Peter:
This is John Saxon, K5ENQ, in Pearland, TX, and I have experienced what appears to be the identical symptoms. Also have contacted support, got some suggestions, tried them to no avail (mostly dealing with possible rf grounding issues). Like you, it may operate perfectly for hours or days, then later I need to ATU and I get the same results as yours when yours fails. My serial #3524. Like you I am not inclined to send it in for fear it may not fail. I also experience these somewhat intermittent failures when loading into a dummy load on my bench. I am sorry I have nothing useful to convey, other than that you are not alone :-) If anyone does come up with suggestions/solutions, please broadcast to group as there are now at least 2 folks with what appears to be the same issue(s). Good luck to us all,JohnK5ENQ On Friday, March 1, 2019, 8:48:16 AM CST, Peter Lock <[hidden email]> wrote: Good day Late last year, my K3 (no 6957) developed a fault. The symptoms were: 1. No power output when keying the rig 2. TX LED on when keyed, (sidetone generated in CW mode) 3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0 - 100 4. ATU tune command: relays clicking, TX LED on, no power output, no indication on SWR meter; two horizontal dashes in the VFO A display area where normally one would see the resolving SWR; in VFO B area 5.0W is indicated 5. TX gain calibration failed on 5W and 50W; mW TX calibration gain OK I contacted Elecraft Support who suspected a failure of the LPA PA transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA board was found to be dead. Q4 and Q5 were replaced, re-biased and tested. On getting the rig back, the same symptoms were present, but lasted only a short while and the rig then performed normally, enough to have a couple of QSOs, but then failed. Since then the same symptoms have been present intermittently. I asked a friend who also has a K3 to try the rig to make sure I was not doing something silly. For about 20 minutes after switch on the symptoms were present, then for no apparent reason the rig performed normally for approximately 10 minutes before failing again. We were testing by repeatedly invoking ATU tune functions on different bands. Since then, the rig will work or not work on switch on; it has worked flawlessly for several hours but sometimes will present only the listed symptoms for several hours after switch on. When it is working, it all works, specifically the TX gain calibration completes normally After several days of performing normally, I relocated the rig to my alternative operating location; it did not work, with the same symptoms. Elecraft Support has been as exemplary as ever, but they are loth for me to return the rig when it may well sit on the test bench being smug and behaving normally. It seems to me that the possibilities are (i) a dry solder joint (ii) a loose connection or (iii) a component on the verge of failing. I think I should next dismantle and reassemble the rig to try to exclude option (ii), and perhaps find either (i) or (iii), although needle and haystack comes to mind... Has anyone suffered similar problems and found a solution, or can someone advise where I should concentrate my search? Peter M0RYB -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Intermittent loss of power output K3
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In reply to this post by Peter Lock
What happens when the rig is connected to a dummy load?
73 de RayK2ULRKX3 #211 -----Original Message----- From: John Saxon via Elecraft <[hidden email]> To: elecraft <[hidden email]>; Peter Lock <[hidden email]> Sent: Fri, Mar 1, 2019 10:12 am Subject: Re: [Elecraft] Intermittent loss of power output K3 Peter: This is John Saxon, K5ENQ, in Pearland, TX, and I have experienced what appears to be the identical symptoms. Also have contacted support, got some suggestions, tried them to no avail (mostly dealing with possible rf grounding issues). Like you, it may operate perfectly for hours or days, then later I need to ATU and I get the same results as yours when yours fails. My serial #3524. Like you I am not inclined to send it in for fear it may not fail. I also experience these somewhat intermittent failures when loading into a dummy load on my bench. I am sorry I have nothing useful to convey, other than that you are not alone :-) If anyone does come up with suggestions/solutions, please broadcast to group as there are now at least 2 folks with what appears to be the same issue(s). Good luck to us all,JohnK5ENQ On Friday, March 1, 2019, 8:48:16 AM CST, Peter Lock <[hidden email]> wrote: Good day Late last year, my K3 (no 6957) developed a fault. The symptoms were: 1. No power output when keying the rig 2. TX LED on when keyed, (sidetone generated in CW mode) 3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0 - 100 4. ATU tune command: relays clicking, TX LED on, no power output, no indication on SWR meter; two horizontal dashes in the VFO A display area where normally one would see the resolving SWR; in VFO B area 5.0W is indicated 5. TX gain calibration failed on 5W and 50W; mW TX calibration gain OK I contacted Elecraft Support who suspected a failure of the LPA PA transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA board was found to be dead. Q4 and Q5 were replaced, re-biased and tested. On getting the rig back, the same symptoms were present, but lasted only a short while and the rig then performed normally, enough to have a couple of QSOs, but then failed. Since then the same symptoms have been present intermittently. I asked a friend who also has a K3 to try the rig to make sure I was not doing something silly. For about 20 minutes after switch on the symptoms were present, then for no apparent reason the rig performed normally for approximately 10 minutes before failing again. We were testing by repeatedly invoking ATU tune functions on different bands. Since then, the rig will work or not work on switch on; it has worked flawlessly for several hours but sometimes will present only the listed symptoms for several hours after switch on. When it is working, it all works, specifically the TX gain calibration completes normally After several days of performing normally, I relocated the rig to my alternative operating location; it did not work, with the same symptoms. Elecraft Support has been as exemplary as ever, but they are loth for me to return the rig when it may well sit on the test bench being smug and behaving normally. It seems to me that the possibilities are (i) a dry solder joint (ii) a loose connection or (iii) a component on the verge of failing. I think I should next dismantle and reassemble the rig to try to exclude option (ii), and perhaps find either (i) or (iii), although needle and haystack comes to mind... Has anyone suffered similar problems and found a solution, or can someone advise where I should concentrate my search? Peter M0RYB -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Intermittent loss of power output K3
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Ray:
I get the same relay chatter, no display of SWR and no output. Some time later I may do the same ATU and it works. Appears to do the same thing as when attempting to load an actual antenna. Because this discussion has begun, I think I will set up again on the bench and see if it will fail. Will be later in the day, I will report results. --JohnK5ENQ On Friday, March 1, 2019, 9:19:43 AM CST, Raymond Sills <[hidden email]> wrote: What happens when the rig is connected to a dummy load? 73 de RayK2ULRKX3 #211 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Intermittent loss of power output K3
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In reply to this post by Peter Lock
Look at the two diodes in the SWR/watt meter circuit. These two diode are
critical to the operation of the K3. These are the foundation of the K3s ALC implementation. Ive had to replace them. Lee K0WA On Fri, Mar 1, 2019, 8:47 AM Peter Lock <[hidden email]> wrote: > Good day > > Late last year, my K3 (no 6957) developed a fault. The symptoms were: > 1. No power output when keying the rig > 2. TX LED on when keyed, (sidetone generated in CW mode) > 3. Single bar showing on the RF power meter, whatever scale, ie 0 - 10 or 0 > - 100 > 4. ATU tune command: relays clicking, TX LED on, no power output, no > indication on SWR meter; two horizontal dashes in the VFO A display area > where normally one would see the resolving SWR; in VFO B area 5.0W is > indicated > 5. TX gain calibration failed on 5W and 50W; mW TX calibration gain OK > > I contacted Elecraft Support who suspected a failure of the LPA PA > transistor(s) and I shipped the rig to Watsonville where Q4 on the LPA > board > was found to be dead. Q4 and Q5 were replaced, re-biased and tested. > > On getting the rig back, the same symptoms were present, but lasted only a > short while and the rig then performed normally, enough to have a couple of > QSOs, but then failed. Since then the same symptoms have been present > intermittently. I asked a friend who also has a K3 to try the rig to make > sure I was not doing something silly. For about 20 minutes after switch on > the symptoms were present, then for no apparent reason the rig performed > normally for approximately 10 minutes before failing again. We were > testing > by repeatedly invoking ATU tune functions on different bands. Since then, > the rig will work or not work on switch on; it has worked flawlessly for > several hours but sometimes will present only the listed symptoms for > several hours after switch on. > > When it is working, it all works, specifically the TX gain calibration > completes normally > > After several days of performing normally, I relocated the rig to my > alternative operating location; it did not work, with the same symptoms. > > Elecraft Support has been as exemplary as ever, but they are loth for me to > return the rig when it may well sit on the test bench being smug and > behaving normally. It seems to me that the possibilities are (i) a dry > solder joint (ii) a loose connection or (iii) a component on the verge of > failing. I think I should next dismantle and reassemble the rig to try to > exclude option (ii), and perhaps find either (i) or (iii), although needle > and haystack comes to mind... Has anyone suffered similar problems and > found a solution, or can someone advise where I should concentrate my > search? > > Peter > M0RYB > > > > -- > Sent from: http://elecraft.365791.n2.nabble.com/ > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Peter Lock
Hi Peter;
It definitely had one bad FET on the LPA when it was here, I do not see in the report that it was intermittent, so I may not have looked closely for those types of failures. If you are sure it makes MW power when it is in the failure state, then it is highly likely the LPA. Inspect D1 closely, I have seen one side have poor solder, or it can heat and the solder crystallize. Re-flow solder. Pull the KPA3 but leave the KPAIO3 riser board and you can run it with just the LPA. Disregard errors about KPA3 or set it to "not inst" while you are working on it. Then set for several watts (not 5 exactly) and long press XMIT to go into TUNE, IE transmit a carrier. (TUN PWR must be at "nor"). Then take a stick and tap around on the LPA. Around D1. Also the green/red enamel on T1 & 2 can fail and the windings can short. Tap the three bias pots, sometimes they fail internally, or their solder points. Look at all parts for solder problems. You can put it in the fridge and chill it down to encourage failure, or leave it on for an hour with a blanket over it to heat it up. Keith WE6R ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Intermittent loss of power output K3
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In reply to this post by Peter Lock
Thank you, Keith.
It was indeed a poor solder joint on one end of D1 on the LPA board; there was a hairline gap between the solder and the terminal of the diode. Reflowing the solder has cured the problem. Peter M0RYB Hi Peter; It definitely had one bad FET on the LPA when it was here, I do not see in the report that it was intermittent, so I may not have looked closely for those types of failures. If you are sure it makes MW power when it is in the failure state, then it is highly likely the LPA. Inspect D1 closely, I have seen one side have poor solder, or it can heat and the solder crystallize. Re-flow solder. Pull the KPA3 but leave the KPAIO3 riser board and you can run it with just the LPA. Disregard errors about KPA3 or set it to "not inst" while you are working on it. Then set for several watts (not 5 exactly) and long press XMIT to go into TUNE, IE transmit a carrier. (TUN PWR must be at "nor"). Then take a stick and tap around on the LPA. Around D1. Also the green/red enamel on T1 & 2 can fail and the windings can short. Tap the three bias pots, sometimes they fail internally, or their solder points. Look at all parts for solder problems. You can put it in the fridge and chill it down to encourage failure, or leave it on for an hour with a blanket over it to heat it up. Keith WE6R ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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