Re: [Elecraft] KE8UW Re: Just finished K2 and finals look to be oscillating at 450KHz...
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 >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 >>> Subject: Re: [Elecraft] Just built K2 and finals seem to be oscillating... >>> >>> To: c-haw...@illinois.edu >>> Cc: elecraft >>> >>> 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
Re: [Elecraft] KE8UW Re: Just finished K2 and finals look to be oscillating at 450KHz...
Chuck, Since you have a 'scope, I would suggest you remove the PA transistors from the picture and see if the oscillation persists. You can easily de-solder T3 which will remove voltage from the PA collectors. If you still have the oscillation at the base of Q7/8 (or at the collector) of Q6, then you can more easily troubleshoot it without fear of damaging the PA transistors. Q6 can similarly be taken out of the operating condition by removing a choke or resistor. I don't have the schematics with me while on vacation, so you will have to find out which one on your own. 73, Don W3FPR C. J. Hawley wrote: > 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 > > __ 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
Re: [Elecraft] KE8UW Re: Just finished K2 and finals look to be oscillating at 450KHz...
Good idea...I'm at that stage where I need to check parts and try to isolate. The receiver and all works well. Thanks, Chuck, KE9UW Original message >Date: Wed, 21 Oct 2009 08:42:52 -0400 >From: Don Wilhelm >Subject: Re: [Elecraft] KE8UW Re: Just finished K2 and finals look to be >oscillating at 450KHz... >To: c-haw...@illinois.edu >Cc: elecraft > >Chuck, > >Since you have a 'scope, I would suggest you remove the PA transistors >from the picture and see if the oscillation persists. You can easily >de-solder T3 which will remove voltage from the PA collectors. >If you still have the oscillation at the base of Q7/8 (or at the >collector) of Q6, then you can more easily troubleshoot it without fear >of damaging the PA transistors. >Q6 can similarly be taken out of the operating condition by removing a >choke or resistor. I don't have the schematics with me while on >vacation, so you will have to find out which one on your own. > >73, >Don W3FPR > >C. J. Hawley wrote: >> 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 >> >> __ 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
Re: [Elecraft] KE8UW Re: Just finished K2 and finals look to be oscillating at 450KHz...
Thanks so much for the help. The problem was C120...the one in the middle between two close in caps. Hard to see the value. Had to get serious and bend one over. Figures it would be that one. I had the value .001uF instead of .01uF. You were so correct. Made me look closer. Thanks for your patience, ability, and experience. The alignment seems to be going well so far. Perfect tuning wand for those inductors. All done on that and buttoned up. All works and works well. I need to do the filters now...maybe Spectrogram. I'm a little confused if it is free or what, but I'll figure it out. I have made use of the latest manual on line for some of the later clarifications and info. Thanks for having these on line. And thanks Don and Michael for your suggestions along these same lines. Chuck, KE9UW Original message >Date: Wed, 21 Oct 2009 11:39:06 -0700 >From: Gary Surrency >Subject: KE8UW Re: Just finished K2 and finals look to be oscillating at >450KHz... >To: c-haw...@illinois.edu > > If a close inspection does not find it, a scope or > an RF probe can be a big help too. > > There should be just a little RF leakage at the > junction of D3, D4 when in transmit, but next to > nothing at the anode of D3 or D5. D5 and C110 shunt > any T-R switch leakage to ground through C108. See > the schematic. If there is RF present at these > points, it usually means the T-R switch has poor > isolation. > > Sometimes it helps for troubleshooting to remove T3 > so the PA transistors do not have 12V to operate and > become damaged. Place a 10 ohm resistor across the > base lead of Q7, Q8 to provide a load for Q6 and T2. > Now you can leave off the bottom cover for easier > troubleshooting if the removal of the DC supply to > PA transistors did not stop the oscillations. > > But in almost all cases I have repaired, there is an > incorrect part or bad connection in the Q5-Q8 area > if the PAs are oscillating and it is not being > caused by poor T-R switch isolation (removal of > jumper W1 will show if the RF feedback is from the > output of the PAs to the input of Q5. > > An open RFC can be the problem too, if the DC bias > is not getting to some of the T-R switch parts. > > D1, D5 are biased ON in TX, where D2-D4 and Q2 are > biased ON in RX. > > Some builders have left out the two sets of ferrite > beads at Z1, Z2 on either side of T3. Be sure they > are there, and it is OK for them to touch the pins > of the PA transistors since they are non-conductive. > > Some folks wind T4 correctly but then install it in > reverse. It has to be installed with the green wires > closer to T3, and the two bare wire links go > straight thru each hole of the core, and are not > wound around to the other hole (just a link from > 5-6, and 7-8 on the PCB.) > > I've also see many rigs with Q2 reversed which will > definitely cause self oscillation of the > transmitter. Its wider side should align with the > flat on the PCB. > > Either of the caps across the secondary of T1 or T2 > will cause oscillation if they are damaged, > incorrect values, or missing.RFC6 is critical for > stability too, and must not be open nor missing the > correct parts at C120 or R48. > > All caps around Q5, Q6 are critical as to value, > esp. C115, C119. Be sure you did not use a .001 for > a .01 or 0.1 for example. > > Also check the DC bias on Q6 as I mentioned, and if > it is more than 1.0 to 1.1VDC, replace R46 with a > 390 ohm resistor. The 2SC5739 we now use for Q6 > often needs a lower bias. > > Again, look very very closely at the PCB, parts, and > soldering and you might find the problem just with > your eyes. > > -- > 73, Gary AB7MY > = > supp...@elecraft.com > Elecraft Technical Support > > > C. J. Hawley wrote: > > Thanks again for the help. I checked all the 4007's with a Simpson 360 just > to make sure the cathodes were where they belonged. I can still see the > outline on the board as well. I will check them visually again. > Not discouraged...as an EE I designed and debugged electronics for chemistry > research for 35 years at the U of IL. So I have had my share of late Friday > nights trying to get something running before the chemist's sample died over > the weekend. > Thanks again again. I'll follow these ideas and I have been avoiding > disassembling anything to diagnose (lazy). But that will just have to be part > of the fun. > I'll let you know what I find...embarassed or not...heh. > > Chuck, KE9UW > > Original message > > > Date: Wed, 21 Oct 2009 08:50:07 -0700 > From: Gary Surrency > Subject: Re: KE8UW Re: Just finished K2 and finals look to be oscillating at > 450KHz... > To: c-haw...@illinois.edu > > Are you sure there are no reversed 1N4007 diodes in > the T-R switch? > > Try clipping jumper wire W1 behind T4. If there is > any feedback path from the output of the PA st
Re: [Elecraft] KE8UW Re: Just finished K2 and finals look to be oscillating at 450KHz...
Chuck, Spectrogram version 5.17 is freeware and matches the screenshots for setup. See the information (and download) at Tom Hammond's website www.n0ss.net. If you want extended information about K2 dial calibration and filter setup, take a look at my website article on K2 Dial Calibration - www.w3fpr.com 73, Don W3FPR C. J. Hawley wrote: > Thanks so much for the help. The problem was C120...the one in the middle > between two close in caps. Hard to see the value. Had to get serious and bend > one over. Figures it would be that one. I had the value .001uF instead of > .01uF. > You were so correct. Made me look closer. > Thanks for your patience, ability, and experience. > The alignment seems to be going well so far. Perfect tuning wand for those > inductors. All done on that and buttoned up. All works and works well. I need > to do the filters now...maybe Spectrogram. I'm a little confused if it is > free or what, but I'll figure it out. > I have made use of the latest manual on line for some of the later > clarifications and info. Thanks for having these on line. > And thanks Don and Michael for your suggestions along these same lines. > Chuck, KE9UW > > __ 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
