Yes the W6 point gets 8 volts either thru the diode D2 or D6 depending on whether in receive or xmit. I think I have an oscillator at Q5-Q6. I am checking all the feedback chokes and capacitors. I may need to unsolder C118 and see if it is infact a capacitor inside the shell and maybe also C120. RFC6 checks ok, R49, R470, etc. Thanks for the interest and help.
Chuck, KE9UW ---- Original message ---- >Date: Tue, 20 Oct 2009 23:40:36 -0400 >From: Don Wilhelm <d...@w3fpr.com> >Subject: Re: [Elecraft] Just built K2 and finals seem to be oscillating... >To: c-haw...@illinois.edu > >Chuck, > >I have given you about all the info I can until I can refer to the >schematics and make a guess about where the 450 Hz might be coming >from. I am currently thinking that there should be no DC at W6, but I >could be wrong on that. > >As far as the sidetone source - yes, with firmware 2.04r, you must add >the sidetone source wiring change to obtain sidetone for all control >boards below SN 3000 - whether or not you have the KIO2 or KPA100 >installed. The statements in the firmware document override since they >are dated later than the A to B upgrade or the KIO2 or KPA100 >instructions. Version 2.04r firmware eliminated the U6-25 sidetone >output option and will save a lot of support effort in the future. > >73, >Don W3FPR > > >C. J. Hawley wrote: >> Thanks. I went back and re-read his note and he did mention K2-T2 as well. >> Then I went to the newest manual and K2-T1 and K2-T2 are now shown wound the >> way he did them for me. All reverse from the original manual. So that's not >> an issue I see. >> I still don't have a solution though. I checked 8T, 8R, measured all the D1 >> thru D4 diodes, took out the 160M board and shorted J14 to restore W1, >> resistance checked to see that all the chokes, etc. are installed in the T-R >> switch area. >> >> After more careful checking with the power knob all the way down, I get >> about 3 vpp at W6 riding on 8 vdc. I get very small voltage at BPF on >> transmit and as well on Xmixer and buffer. 40 vpp with 8 vdc on D3-D4 >> cathodes, 60 vpp at 0 vdc on W1 (with 160 removed), and the same 60 vpp at 0 >> vdc on the output ant jack. Fundamental freq is about 450KHz. >> >> I also read the instructions for rev 2.04 firmware which said to revise the >> A board according to KIO2 mod details for sidetone, but I kept going back to >> rev B mod page where it said I didn't have to if I didn't have KIO2. The >> issue is that the new rev 2.04 firmware does not have the option to use >> U6-25. It only allows U8-4. Once I cut the trace, etc. all works well for >> the sidetone. >> >> Beats me... >> >> Chuck, KE9UW >> >> ---- Original message ---- >> >>> Date: Tue, 20 Oct 2009 17:56:27 -0400 >>> From: Don Wilhelm <w3...@embarqmail.com> >>> Subject: Re: [Elecraft] Just built K2 and finals seem to be oscillating... >>> >>> To: c-haw...@illinois.edu >>> Cc: elecraft <elecraft@mailman.qth.net> >>> >>> 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 ______________________________________________________________ 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
