20 meter problem on new K2
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I just noticed that my K2 build 43xx is almost totally dead on 20 meters. I
think all the other bands are OK. I hooked up my N-Gen and could not hear anything on 20. I thought I could use a scope to follow the generators noise signal but the scope makes about as much noise as the generator when going through the bandpass circuit. I am guessing it is probably bandpass or low pass and I need to start checking to make sure the relays are making contact, etc.?? It worked when I built it a couple months ago and am not sure when it quit as I dont use 20 often. This K2 is totally optioned and I have removed the 100 watt PA to make sure it is not the culprit. Any comments on the best way to trouble shoot this? Thanks and 73, Rich kd0zv _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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A proper signal generator is just about essential to do the job. The problem
is that you need a fair amount of signal to get any indication on the average oscilloscope. The normal method is to use an RF millvoltmeter to trace the path. You can use the Elecraft provided RF probe and a DVM providing you can inject an on frequency signal of sufficient level to work through the RX bandpass filters, etc. Elecraft give a figure of 140mV from the signal generator to carry out this test There is a good description how to go about it in the rev F, K2 manual Appendix E, Troubleshooting page 11. It is possible under extreme circumstances to use a TX into a dummy load as a signal source, but needs extreme care how you would extract sufficient level without smoking the RX front end. Much better to use a suitable signal generator. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Rich McCabe
I would forget checking relays for the moment. Take a look at the coupling
capacitors for the 20m/30m circuit, the ones installed on the bottom of the board. Make sure solder flowed through to the top of the board for good connection to the traces up there. This was my 20m problem. 73, Joe, aa4nn >I just noticed that my K2 build 43xx is almost totally dead on 20 meters. I >think all the other bands are OK. > > I hooked up my N-Gen and could not hear anything on 20. I thought I could > use a scope to follow the generators noise signal but the scope makes > about as much noise as the generator when going through the bandpass > circuit. > > I am guessing it is probably bandpass or low pass and I need to start > checking to make sure the relays are making contact, etc.?? > > It worked when I built it a couple months ago and am not sure when it quit > as I dont use 20 often. This K2 is totally optioned and I have removed > the 100 watt PA to make sure it is not the culprit. > > Any comments on the best way to trouble shoot this? > > Thanks and 73, > > Rich > kd0zv > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft Help: > http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by G3VVT
Thanks for the tips guys. After thinking about it, I am not 100% positive it worked when new. I do know it went through the alignment without problems, so I better check my wound coils just to be safe. Everything else seems to work OK and the only issue is lack of sensitivity on 20 meters.
73, Rich ----- Original Message ----- From: [hidden email] To: [hidden email] ; [hidden email] Sent: Saturday, October 30, 2004 7:16 PM Subject: Re: [Elecraft] 20 meter problem on new K2 A proper signal generator is just about essential to do the job. The problem is that you need a fair amount of signal to get any indication on the average oscilloscope. The normal method is to use an RF millvoltmeter to trace the path. You can use the Elecraft provided RF probe and a DVM providing you can inject an on frequency signal of sufficient level to work through the RX bandpass filters, etc. Elecraft give a figure of 140mV from the signal generator to carry out this test There is a good description how to go about it in the rev F, K2 manual Appendix E, Troubleshooting page 11. It is possible under extreme circumstances to use a TX into a dummy load as a signal source, but needs extreme care how you would extract sufficient level without smoking the RX front end. Much better to use a suitable signal generator. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: 20 meter problem on new K2
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In reply to this post by Rich McCabe
Did you "seat" the band pass filter trimmer caps, Rich?
Many of those trimmer capacitors come from the factory needing to be twirled around a number of times to "seat" them so the sliding contact has electrical continuity. Just put your screwdriver in the slot and twirl it around a bunch of times, then re-try the alignment procedure. That CAN happen after the rig has been successfully aligned once. Apparently the contacts need a little 'exercising' to make them seat completely. Once that is done, they are fine. There's nothing wrong with the trimmers. That's the most common reason for a dead band, right up there with perhaps a dreaded PTTL (poorly-tinned-toroid-lead). Normally a PTTL won't make the rig quit though. It won't work from the first. If you didn't get ALL the enamel burned/scraped off of a toroid lead or you pulled the lead through the board passed the tinned segment so enamel-covered wire was in the hole, you might not be making electrical contact on that lead. Leads that aren't tinned properly look fine when soldered unless you look VERY closely at the wire. You'll often see a tiny ring of dark that looks like rosin around the conductor. It's actually the enamel. In that case the wire is "trapped" in the solder blob and won't pull out, but it isn't making electrical contact either. Ron AC7AC -----Original Message----- I just noticed that my K2 build 43xx is almost totally dead on 20 meters. I think all the other bands are OK. I hooked up my N-Gen and could not hear anything on 20. I thought I could use a scope to follow the generators noise signal but the scope makes about as much noise as the generator when going through the bandpass circuit. I am guessing it is probably bandpass or low pass and I need to start checking to make sure the relays are making contact, etc.?? It worked when I built it a couple months ago and am not sure when it quit as I dont use 20 often. This K2 is totally optioned and I have removed the 100 watt PA to make sure it is not the culprit. Any comments on the best way to trouble shoot this? Thanks and 73, Rich kd0zv _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Yes, I remember reading about seating the caps. So I gave those two about 20
spins and did not help. The radio seems to peak OK going through the alignment. Just seems to have no sensitivity. I just pulled out a TenTec RX-320 and a S-9 singal on the TenTec is only a single bar on the K2. I have to crank the audio almost all the way up to listen as well. I doubt in my case it is tinning problems. I am prone to do stupid things but I am pretty good with solder and removing the enamel on the wire. NOT to say it isnt possible. I am surprised I did not notice this before but as I said, I am never on 20. Its a significant difference in audio as you switch to 20. Just to be safe I will check "trace to trace" on the circuit board to make sure the torroids are making good contact :) 73, Rich ----- Original Message ----- From: "Ron D'Eau Claire" <[hidden email]> To: "'Rich McCabe'" <[hidden email]>; "'Elecraft Reflector'" <[hidden email]> Sent: Saturday, October 30, 2004 7:54 PM Subject: RE: [Elecraft] 20 meter problem on new K2 > Did you "seat" the band pass filter trimmer caps, Rich? > > Many of those trimmer capacitors come from the factory needing to be > twirled > around a number of times to "seat" them so the sliding contact has > electrical continuity. Just put your screwdriver in the slot and twirl it > around a bunch of times, then re-try the alignment procedure. That CAN > happen after the rig has been successfully aligned once. Apparently the > contacts need a little 'exercising' to make them seat completely. Once > that > is done, they are fine. There's nothing wrong with the trimmers. > > That's the most common reason for a dead band, right up there with perhaps > a > dreaded PTTL (poorly-tinned-toroid-lead). Normally a PTTL won't make the > rig > quit though. It won't work from the first. > > If you didn't get ALL the enamel burned/scraped off of a toroid lead or > you > pulled the lead through the board passed the tinned segment so > enamel-covered wire was in the hole, you might not be making electrical > contact on that lead. > > Leads that aren't tinned properly look fine when soldered unless you look > VERY closely at the wire. You'll often see a tiny ring of dark that looks > like rosin around the conductor. It's actually the enamel. In that case > the > wire is "trapped" in the solder blob and won't pull out, but it isn't > making > electrical contact either. > > Ron AC7AC > > > > -----Original Message----- > I just noticed that my K2 build 43xx is almost totally dead on 20 meters. > I > think all the other bands are OK. > > I hooked up my N-Gen and could not hear anything on 20. I thought I could > use a scope to follow the generators noise signal but the scope makes > about > as much noise as the generator when going through the bandpass circuit. > > I am guessing it is probably bandpass or low pass and I need to start > checking to make sure the relays are making contact, etc.?? > > It worked when I built it a couple months ago and am not sure when it quit > as I dont use 20 often. This K2 is totally optioned and I have removed > the > 100 watt PA to make sure it is not the culprit. > > Any comments on the best way to trouble shoot this? > > Thanks and 73, > > Rich > kd0zv > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Rich,
If you obtained a peak, you should have similar sensitivity on 20 meters as you have on 40 meters - unless you have a problem in the lowpass filter area. As a test, connect the antenna to the W1 jumper (or the W6 jumper) to bypass the LPF. If the signal level increases, you will find the cause in the LPF. The same LPF is used by both 30 and 20 meters, so a LPF soldering problem on 20 meters should show up on 30 too. About the only thing that would cause OK behavior for 30 and bad behavior for 20 would be incorrect component values making the cutoff frequency too low. Check the turns on L18, L19 and L20 (re-check the core type too) and check capacitors C197 thru C203 for correct values. 73, Don W3FPR ----- Original Message ----- > Yes, I remember reading about seating the caps. So I gave those two about > 20 spins and did not help. > > The radio seems to peak OK going through the alignment. Just seems to > have no sensitivity. I just pulled out a TenTec RX-320 and a S-9 singal on > the TenTec is only a single bar on the K2. I have to crank the audio > almost all the way up to listen as well. > > I doubt in my case it is tinning problems. I am prone to do stupid things > but I am pretty good with solder and removing the enamel on the wire. NOT > to say it isnt possible. > > I am surprised I did not notice this before but as I said, I am never on > 20. Its a significant difference in audio as you switch to 20. > > Just to be safe I will check "trace to trace" on the circuit board to make > sure the torroids are making good contact :) > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Rich McCabe
I just got back around to working on this "20 meter problem" and it turns
out there is no problem. Rich KE0X was on the right track. The K2 remembers the rANT setting per band. Somehow 20 meters got set to receive antenna. I did not catch that the rANT was switching in on 20 only. Now I feel stupid. Good reason for 20 mtr receive being weak huh? 73, Rich kd0zv ----- Original Message ----- From: "Rich Lentz" <[hidden email]> To: "'Rich McCabe'" <[hidden email]> Sent: Saturday, October 30, 2004 5:46 PM Subject: RE: [Elecraft] 20 meter problem on new K2 > Might want to verify that the correct antenna (the V is not above ANT2) is > selected and it could be the Receive antenna is not selected (Menu - rAnt > OFF) > > Rich > KE0X > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Rich McCabe > Sent: Saturday, October 30, 2004 6:28 PM > To: Elecraft Reflector > Subject: [Elecraft] 20 meter problem on new K2 > > > I just noticed that my K2 build 43xx is almost totally dead on 20 meters. > I > think all the other bands are OK. > > I hooked up my N-Gen and could not hear anything on 20. I thought I could > use a scope to follow the generators noise signal but the scope makes > about > as much noise as the generator when going through the bandpass circuit. > > I am guessing it is probably bandpass or low pass and I need to start > checking to make sure the relays are making contact, etc.?? > > It worked when I built it a couple months ago and am not sure when it quit > as I dont use 20 often. This K2 is totally optioned and I have removed > the > 100 watt PA to make sure it is not the culprit. > > Any comments on the best way to trouble shoot this? > > Thanks and 73, > > Rich > kd0zv > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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