K2 Transmitter and KAT2 failures
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Below is some of the text that I sent to Gary.
Basically, if I use the KAT2 to tune my 40m attic dipole the PA finals will short out. I haven't tryied to tune any other antennas because I don't want to pay for any more PA kits ($18.50 'ish each time I tune up). Also, CW is un-usable above 80m and no CW output on 10m (SSB and "tune" yield 8.5W) See text below... 73, Damon KC5CQW Copied text from support email: On 40m-10m when I release the CW key or mic PTT in CW mode, the moment it is released I get a power spike resulting in a HiCur warning. On 12m and 10m I have no output during key down; Only the power spike. (CW only, SSB is fine) If the tune button is activated, The radio will give about 11w Max on 12m and 8.5w on 10m. All other bands yield 12-15W max. At the time of the last PA meltdown, I was able to tune my 40m dipole on 80, 40 and 10m; It failed at 30m. There seems to be no rhyme or reason as to when a failure will occur. It has happened at different frequencies. I am reluctant to use the KAT2 except in bypass from this point on. I don't seem to have any problems with my MFJ-969 Versa Tuner II. During some KAT2 troubleshooting, I found that the voltage on pin 1 of U4 was about 2.5VDC (3-4V spec at 5W) with a leg of R6 lifted. Perhaps I'm not having a mechanical short on the LC board. Maybe the SWR/Power bridge is sending the wrong data. If I tune up on 10m into my dummy load, the K2 reports a 2.1:1 SWR. My MFJ-969 read 1.05:1 The best I can tell, everything seems to be fine on the SSB modes. I can't help but think however, if a problem in CW if occurring that I may have some distortion on SSB. |
Re: K2 Transmitter and KAT2 failures
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Damon,
I would speculate that you have bad diodes in the KAT2 wattmeter (D1 and D2), or there is some other problem with the wattmeter in the KAT2. Try this test: 1) Put an external wattmeter (or other power measuring device) on the output of the K2 and make certain you are connected to a good 50 ohm dummy load. 2) Set the power to 4 or 5 watts and set the KAT2 to CAL P and press TUNE - check to be certain the K2 is controlling the power output near the requested level. 3) Evaluate the result: If the power goes to maximum output (but displays 0.1 or 0.2 watts - which is actually zero), then you have a problem with the KAT2 wattmeter circuit, and it it was working before, the most likely cause is that the diodes have been zapped. OTOH, if the K2 display shows some reasonable power output, but is quite different from the external wattmeter, you need to calibrate the KAT2 wattmeter - start with the balance adjustment, then calibrate the power output and finally calibrate the SWR. The adjustments must be done in that order - if you go back to a prior adjustment, you have to re-do the other adjustments. Fact is you may have only the forward diode bad but not the refl diode - that would cause a higher than normal SWR to be indicated. Since the diodes were likely damaged by a lightning static surge (yes, it can happen even with an attic antenna), I would recommend replacing both of them if either are suspected of causing a problem. 73, Don W3FPR Damon - KC5CQW wrote: > Below is some of the text that I sent to Gary. > Basically, if I use the KAT2 to tune my 40m attic dipole the PA finals will > short out. > I haven't tryied to tune any other antennas because I don't want to pay for > any more PA kits ($18.50 'ish each time I tune up). > Also, CW is un-usable above 80m and no CW output on 10m (SSB and "tune" > yield 8.5W) > > See text below... > > 73, Damon KC5CQW > > 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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Don,
Actually, in CalP mode on 10m the KAT2 reports 14.2W and my external shows 8.5W. I calibrated the KAT2 on 40m per the manual, should I set the FWD/REF pots on a different band? The closest setting of C55? in CALn was 006 as displayed on the K2's LCD. I did find that the test point voltage at pin 1 on U4 was about 2.5V @ 5W (3-4V spec). I did verify that everything was correct on and around T1. The good news is after two months of troubleshooting, I finally have the radio working enough to make my first contact with it today. The other op. was in a bit of a hurry to QSY but, he did say that the audio sounded just fine (7.180MHz LSB with W8ERN). 73, Damon
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In reply to this post by KC5CQW
Now I have a "new" problem. It seems that my front panel is very positional when I mate it back onto the K2 main body. Audio is lost and really strange things happen when I plug in the MH2 mic...
What gives... Damon KC5CQW
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I had a 1D 10 T error... Problem found to last post; Wireing error within the MH2.
I did the fixed audio mod to the mic connector at pin 8 then wired the MH2 wrong... Go figure.
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In reply to this post by KC5CQW
I had a 1D 10 T error... Problem found to last post; Wireing error within the MH2.
I did the fixed audio mod to the mic connector at pin 8 then wired the MH2 wrong... Go figure.
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In reply to this post by KC5CQW
I had a 1D 10 T error... Problem found to last post; Wireing error within the MH2.
I did the fixed audio mod to the mic connector at pin 8 then wired the MH2 wrong... Go figure.
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In reply to this post by KC5CQW
Ian, try this experiment. Change your AGC Slope to 15. Set RF Gain to maximum with preamp on. Tune in a very strong signal and adjust AF Gain to your maximum comfortable listening level. From now on, don't touch your AF Gain and just vary RF Gain and preamp depending on band noise and signal levels. With Heil Proset headphones, my AF Gain stays at 9 o'clock (1/4 way up) and my RF Gain varies from 50-100%. Most of the time, my AGC Slope stays at 15. 73, Barry N1EU |
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In reply to this post by KC5CQW
Well I did it again, My last set of finals just fried! I was using my manual tuner on 20m at 2W.
I think what's happening is the power spike is overloading the finals at the end of each transmission. Now I no longer believe the KAT2 is responsible since it was out of circuit. I have not been able to find any faults in the KAT2. It just seemed a likely candidate because thats when the failures would occur. I've now proven that theory incorrect. I must have a fault in the LPF or PA sections. To date, I have not been successful in locating the problem. It is long overdue for me to swallow my pride and send the K2 in for service. I think what hurts the most is knowing that it will be something simple like a bad solder joint. I want to thank Don and the everyone else that has helped me to this point. In the 2 1/2 months i've owned this radio, I'm glad to say that at-least I did make one contact on the air! 73, Damon KC5CQW
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Re: K2 Transmitter and KAT2 failures
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Damon,
Now that you are concentrating on the K2 itself, you may want to examine T4 and the low pass filter area carefully. In the LPF, count the turns on each toroid - count only the turns that pass through the center of the core. If there is an extra turn on the toroids, the LPF cutoff frequency will be too low and may even be shunting a lot of your signal to ground. Likewise, count the turns on T4 and compare that with the manual. The ratio of turns is important to allow the PA transistors to see the correct impedance match. 73, Don W3FPR Damon - KC5CQW wrote: > Well I did it again, My last set of finals just fried! I was using my > manual tuner on 20m at 2W. > I think what's happening is the power spike is overloading the finals at the > end of each transmission. > Now I no longer believe the KAT2 is responsible since it was out of circuit. > I have not been able to find any faults in the KAT2. It just seemed a likely > candidate because thats when the failures would occur. > I've now proven that theory incorrect. I must have a fault in the LPF or PA > sections. To date, I have not been successful in locating the problem. > It is long overdue for me to swallow my pride and send the K2 in for > service. I think what hurts the most is knowing that it will be something > simple like a bad solder joint. > I want to thank Don and the everyone else that has helped me to this point. > In the 2 1/2 months i've owned this radio, I'm glad to say that at-least I > did make one contact on the air! > > 73, Damon KC5CQW > > > > Damon - KC5CQW wrote: > >> Below is some of the text that I sent to Gary. >> Basically, if I use the KAT2 to tune my 40m attic dipole the PA finals >> will short out. >> I haven't tryied to tune any other antennas because I don't want to pay >> for any more PA kits ($18.50 'ish each time I tune up). >> Also, CW is un-usable above 80m and no CW output on 10m (SSB and "tune" >> yield 8.5W) >> >> See text below... >> >> 73, Damon KC5CQW >> >> Copied text from support email: >> >> On 40m-10m when I release the CW key or mic PTT in CW mode, the moment it >> is released I get a power spike resulting in a HiCur warning. >> On 12m and 10m I have no output during key down; Only the power spike. (CW >> only, SSB is fine) >> If the tune button is activated, The radio will give about 11w Max on 12m >> and 8.5w on 10m. >> All other bands yield 12-15W max. >> >> >> At the time of the last PA meltdown, I was able to tune my 40m dipole on >> 80, 40 and 10m; It failed at 30m. >> There seems to be no rhyme or reason as to when a failure will occur. It >> has happened at different frequencies. >> I am reluctant to use the KAT2 except in bypass from this point on. >> I don't seem to have any problems with my MFJ-969 Versa Tuner II. >> >> During some KAT2 troubleshooting, I found that the voltage on pin 1 of U4 >> was about 2.5VDC (3-4V spec at 5W) with a leg of R6 lifted. >> Perhaps I'm not having a mechanical short on the LC board. Maybe the >> SWR/Power bridge is sending the wrong data. >> If I tune up on 10m into my dummy load, the K2 reports a 2.1:1 SWR. My >> MFJ-969 read 1.05:1 >> >> The best I can tell, everything seems to be fine on the SSB modes. I can't >> help but think however, if a problem in CW if occurring that I may have >> some distortion on SSB. >> >> >> >> > > > ----- > Damon Wascom KC5CQW > Elecraft K2 #:6351 > Build: 12/28/07-01/01/08 > > > 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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T1-T4 have been completely rewound and reinstalled, all solder joints have been reworked on the RF board including the LPF toroids; They have been recounted and verified good with a DMM, RF probe and signal injector at various test points.
I'm going to send it in for service this week and hopfully Gary can find the problem. My patience for working on and not operating the radio has reached it's limit. I believe that once he has a chance to actually see the symptoms for himself it will be much more clear. By spring, it should be on the air. I can't wait to see what these K2's are really capable of doing.
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