Help-damaged front end?
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I've got a K2 / 100 that has had a dramatic loss of sensitivity. This
occurred after a thunderstorm, when the antennas were disconnected outside the house, but there was still some residual coax feeds (unterminated) still connected to the K2. Where to start to look? Appears to have lost sensitivity on all bands, all modes. Transmit is still fine (at least CW) . Thanks John -- Internal Virus Database is out-of-date. Checked by AVG Free Edition. Version: 7.1.405 / Virus Database: 268.15.9/573 - Release Date: 12/5/2006 _______________________________________________ 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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John,
Yup, thunderstorms can put some big surges on unterminated hunks of coax. If it receives any signals at all and you can tune the signals, then it is unlikely that everything between the mixer and the audio output has been damaged. That leaves only the preamp for active stages - turn the preamp on and off to see if it works, you should see about a 14 dB change (2+ S-units). If the preamp check works out fine, that leaves only the bandpass filters, lowpass filters and the T/R switch in the base K2 and the KPA100. Since you said it transmits fine, the filters are likely not the problem (a filter problem would have more impact on transmit) - the most likely thing is one of the diodes in the T/R switch is damaged. I would first do the DC voltage measurements on the T/R switch diodes in both the base K2 and the KPA100. 73, Don W3FPR > -----Original Message----- > > I've got a K2 / 100 that has had a dramatic loss of sensitivity. This > occurred after a thunderstorm, when the antennas were > disconnected outside > the house, but there was still some residual coax feeds (unterminated) > still connected to the K2. > > Where to start to look? Appears to have lost sensitivity on all > bands, all > modes. Transmit is still fine (at least CW) . > > Thanks > John > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.20/588 - Release Date: 12/15/2006 10:02 AM _______________________________________________ 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 john-477
Before you do anything drastic,
make sure your DSP unit is bypassed. Inadvertent DSP triggering can make you think the receiver is dead. de Joe, aa4nn ----- Original Message ----- From: "john" <[hidden email]> To: <[hidden email]> Sent: Saturday, December 16, 2006 9:13 AM Subject: [Elecraft] Help-damaged front end? > I've got a K2 / 100 that has had a dramatic loss of sensitivity. This > occurred after a thunderstorm, when the antennas were disconnected outside > the house, but there was still some residual coax feeds (unterminated) > still connected to the K2. > > Where to start to look? Appears to have lost sensitivity on all bands, all > modes. Transmit is still fine (at least CW) . > > Thanks > John _______________________________________________ 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 john-477
Hi John:
Consider downloading my "Quick 'n Dirty Signal Tracing Suggestions" for the K2 from my web site at: www.n0ss.net It'll be found in the 'Elecraft K2-Related Files' section. With it, you can start out testing at the innermost part of the receiver RF section and progress outward (toward the antenna) until the signal stop... at which point you've isolated the section where it problem resides. It may not be the BEST way to troubleshoot, but it's relatively easy and requires no special equipment to at least get a pretty good idea of where the problem might be. Good luck, Tom Hammond N0SS At 08:13 AM 12/16/2006, you wrote: >I've got a K2 / 100 that has had a dramatic loss of >sensitivity. This occurred after a thunderstorm, when the antennas >were disconnected outside the house, but there was still some >residual coax feeds (unterminated) still connected to the K2. > >Where to start to look? Appears to have lost sensitivity on all >bands, all modes. Transmit is still fine (at least CW) . > >Thanks >John > > >-- >Internal Virus Database is out-of-date. >Checked by AVG Free Edition. >Version: 7.1.405 / Virus Database: 268.15.9/573 - Release Date: 12/5/2006 > >_______________________________________________ >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 Don Wilhelm-3
For What it is worth, during the course of construction on my K2 I
inadvertently scrambled the K2's eprom storage with ESD. (Electrostatic Discharge) In one instance I had to do a complete reset of the MPU and memory back to the factory defaults. Only at that time did the receiver come back to life again. In my opinion, the little K2 is very susceptible to ESD ( I was wearing a wrist strap) and the thunderstorms you speak of could have definitely jumbled the K2's data storage. /joe ----- Original Message ----- From: "Don Wilhelm" <[hidden email]> To: "john" <[hidden email]>; <[hidden email]> Sent: Saturday, December 16, 2006 7:30 AM Subject: RE: [Elecraft] Help-damaged front end? > John, > > Yup, thunderstorms can put some big surges on unterminated hunks of coax. > > If it receives any signals at all and you can tune the signals, then it is > unlikely that everything between the mixer and the audio output has been > damaged. That leaves only the preamp for active stages - turn the preamp > on > and off to see if it works, you should see about a 14 dB change (2+ > S-units). > > If the preamp check works out fine, that leaves only the bandpass filters, > lowpass filters and the T/R switch in the base K2 and the KPA100. Since > you > said it transmits fine, the filters are likely not the problem (a filter > problem would have more impact on transmit) - the most likely thing is > one > of the diodes in the T/R switch is damaged. > > I would first do the DC voltage measurements on the T/R switch diodes in > both the base K2 and the KPA100. > > 73, > Don W3FPR > > >> -----Original Message----- >> >> I've got a K2 / 100 that has had a dramatic loss of sensitivity. This >> occurred after a thunderstorm, when the antennas were >> disconnected outside >> the house, but there was still some residual coax feeds (unterminated) >> still connected to the K2. >> >> Where to start to look? Appears to have lost sensitivity on all >> bands, all >> modes. Transmit is still fine (at least CW) . >> >> Thanks >> John >> > -- > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.432 / Virus Database: 268.15.20/588 - Release Date: > 12/15/2006 > 10:02 AM > > _______________________________________________ > 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 Tom Hammond-3
Tom,
I argue that it IS the BEST way to BEGIN troubleshooting!!! It is indeed 'Quick', and there is nothing 'Dirty' about it. It may not be complete, but it is the easiest starting point. I use similar techniques all the time - no need to drag out the signal generators and other equipment if it is successful, and the success rate for me is greater than 50% when the receiver is not receiving as it should.. 73, Don W3FPR > -----Original Message----- > > Consider downloading my "Quick 'n Dirty Signal Tracing Suggestions" > for the K2 from my web site at: www.n0ss.net It'll be found in the > 'Elecraft K2-Related Files' section. > > With it, you can start out testing at the innermost part of the > receiver RF section and progress outward (toward the antenna) until > the signal stop... at which point you've isolated the section where > it problem resides. > > It may not be the BEST way to troubleshoot, but it's relatively easy > and requires no special equipment to at least get a pretty good idea > of where the problem might be. > > Good luck, > > Tom Hammond N0SS > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.21/589 - Release Date: 12/15/2006 5:10 PM _______________________________________________ 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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