Just built K2 and finals seem to be oscillating...
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I just finished this K2 rev A with most all mods incl B and cannot do the transmitter alignment.
The finals seem to be oscillating at about 450 KHz on all bands. The power goes to max (17 watts), the current goes to 3 amps, on the Bird meter (50 watt slug) I get about 13 watts showing. The frequency on the scope (and aux counter) appears to be about 450 KHz. I get this frequency on W6 (about 5 vpp and as well larger at the collector of Q6 (about 25vpp) and of course at the collectors of the finals but with a lot of ringing at a higher frequency and at the input to the low pass filters, about 40 vpp...same on all bands. I've checked the transformers, etc for wiring and they appear to be ok. No shorts on the final collectors, etc. Kind of looking for some previous experience with this or some idea of where to go. I also have the latest firmware, rev 2.04 and have no side tone. With the firmware from March 2000, rev 1.04 I have sidetone. The instructions (various years) say the side tone comes from U8 pin 4, I get ac voltage there, the menu says U8-4, but no sound. Thanks, Chuck KE9UW ______________________________________________________________ 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
Chuck, KE9UW
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Thanks, I checked that. Looks ok.
One thing I wondered about is that T1 and T2 were wound differently by the toroid winder fellow that I bought from. He said in his paper included that it was ok with Elecraft. He wound them so that the secondary turns fell in along side the primary turns. The way they were originally specified in the K2 manual (my K2 is serial number 1089, I bought it new but just finishing it) the secondary turns crossed over the primary ones. That is, the secondary was reversed winding direction. Looking at the drawings, I can't see where that would be an issue unless reversing the phase of the rf would be and issue with some kind of stray feedback. Thanks again, Chuck, KE9UW ---- Original message ---- >Date: Tue, 20 Oct 2009 12:53:54 +0200 >From: "Michael van Hauten" <[hidden email]> >Subject: Re: [Elecraft] Just built K2 and finals seem to be oscillating... >To: <[hidden email]> > >Chuck, >i had a similar problem some years ago with one of my k2's. Check D36 on the >bottom side. Im my case d36 was not soldered. The finals and driver got hot, >when i swiched to transmit. >Good luck! > >Michael, DC0ZO > > >----- Original Message ----- >From: "C. J. Hawley" <[hidden email]> >To: <[hidden email]> >Sent: Tuesday, October 20, 2009 4:07 AM >Subject: [Elecraft] Just built K2 and finals seem to be oscillating... > > >>I just finished this K2 rev A with most all mods incl B and cannot do the >>transmitter alignment. >> The finals seem to be oscillating at about 450 KHz on all bands. >> The power goes to max (17 watts), the current goes to 3 amps, on the Bird >> meter (50 watt slug) I get about 13 watts showing. The frequency on the >> scope (and aux counter) appears to be about 450 KHz. I get this frequency >> on W6 (about 5 vpp and as well larger at the collector of Q6 (about 25vpp) >> and of course at the collectors of the finals but with a lot of ringing at >> a higher frequency and at the input to the low pass filters, about 40 >> vpp...same on all bands. >> I've checked the transformers, etc for wiring and they appear to be ok. >> No shorts on the final collectors, etc. Kind of looking for some previous >> experience with this or some idea of where to go. >> >> I also have the latest firmware, rev 2.04 and have no side tone. With the >> firmware from March 2000, rev 1.04 I have sidetone. The instructions >> (various years) say the side tone comes from U8 pin 4, I get ac voltage >> there, the menu says U8-4, but no sound. >> >> Thanks, >> Chuck >> KE9UW >> ______________________________________________________________ >> 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 ______________________________________________________________ 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
Chuck, KE9UW
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Re: Just built K2 and finals seem to be oscillating...
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Chuck,
The winding sense that The Toroid Guy was referring to is T1 and T2 for the KSB2 board, not the base K2. The winding sense on those transformers will make no difference. From your previous post, I see you have an oscillation that appears as far back as W6. That can be a problem muh earlier in the transmit chain, like at the TX mixer or the Transmit buffer. Check the RF levels of the VFO and BFO at the transmit mixer (see the Receive and Transmit Signal Tracing sections in the back of the manual for the normal levels. Also check the frequency at TP2 and TP1 to be certain they are correct - the VFO frequencies for each band are listed on the Schematic Key page. 73, Don W3FPR C. J. Hawley wrote: > Thanks, I checked that. Looks ok. > One thing I wondered about is that T1 and T2 were wound differently by the toroid winder fellow that I bought from. He said in his paper included that it was ok with Elecraft. He wound them so that the secondary turns fell in along side the primary turns. The way they were originally specified in the K2 manual (my K2 is serial number 1089, I bought it new but just finishing it) the secondary turns crossed over the primary ones. That is, the secondary was reversed winding direction. > Looking at the drawings, I can't see where that would be an issue unless reversing the phase of the rf would be and issue with some kind of stray feedback. > > Thanks again, Chuck, KE9UW > > ---- Original message ---- > >> Date: Tue, 20 Oct 2009 12:53:54 +0200 >> From: "Michael van Hauten" <[hidden email]> >> Subject: Re: [Elecraft] Just built K2 and finals seem to be oscillating... >> To: <[hidden email]> >> >> Chuck, >> i had a similar problem some years ago with one of my k2's. Check D36 on the >> bottom side. Im my case d36 was not soldered. The finals and driver got hot, >> when i swiched to transmit. >> Good luck! >> >> Michael, DC0ZO >> >> >> ----- Original Message ----- >> From: "C. J. Hawley" <[hidden email]> >> To: <[hidden email]> >> Sent: Tuesday, October 20, 2009 4:07 AM >> Subject: [Elecraft] Just built K2 and finals seem to be oscillating... >> >> >> >>> I just finished this K2 rev A with most all mods incl B and cannot do the >>> transmitter alignment. >>> The finals seem to be oscillating at about 450 KHz on all bands. >>> The power goes to max (17 watts), the current goes to 3 amps, on the Bird >>> meter (50 watt slug) I get about 13 watts showing. The frequency on the >>> scope (and aux counter) appears to be about 450 KHz. I get this frequency >>> on W6 (about 5 vpp and as well larger at the collector of Q6 (about 25vpp) >>> and of course at the collectors of the finals but with a lot of ringing at >>> a higher frequency and at the input to the low pass filters, about 40 >>> vpp...same on all bands. >>> I've checked the transformers, etc for wiring and they appear to be ok. >>> No shorts on the final collectors, etc. Kind of looking for some previous >>> experience with this or some idea of where to go. >>> >>> I also have the latest firmware, rev 2.04 and have no side tone. With the >>> firmware from March 2000, rev 1.04 I have sidetone. The instructions >>> (various years) say the side tone comes from U8 pin 4, I get ac voltage >>> there, the menu says U8-4, but no sound. >>> >>> Thanks, >>> Chuck >>> KE9UW >>> ______________________________________________________________ >>> 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 >>> > Jack Hawley MOA and RA #224, KE9UW ("Chuck", my first name, for Ham Radio and Lionel Trains). > ______________________________________________________________ > 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 > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.422 / Virus Database: 270.14.23/2448 - Release Date: 10/20/09 10:43:00 > > 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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