++++++++++++++++ See also Troubleshooting (General) ++++++++++++++++ From: david-davis at att.net To: elecraft at mailman.qth.net Subject: Re: [Elecraft] 40 Meter Transmitter Alignment problems - RESOLVED! Date: Thu, 02 Jan 2003 05:58:54 +0000 To All: Thank You to those that replied to my request for assistance. I have resolved the problem with my K2. The problem was that the windings for T3 were crossed and the incorrect leads were soldered in the wrong places. I removed T3 rewound it and replaced soldered. The voltages to Q7 and Q8 immediately appeared as normal. I now have been able to perform the 40-Meter Transmitter Alignment. Thanks again to everyone that responded. This is a great bunch of individuals. Thanks David Davis, KG6MTI david-davis at att.net ----org1-- From: david-davis at att.net To: elecraft at mailman.qth.net Date: Wed, 01 Jan 2003 18:59:25 +0000 Subject: [Elecraft] 40 Meter Transmitter Alignment problems Hello All: This is an update to a post I made the other day. I am trying to perform the 40 meter transmitter alignment. When I get to the portion of the alignment that tells me to put the radio in mode and activate the build in watt meter. I try to adjust L1 for maximum output but the power level stays at 0.1W. I went through the troubleshooting section of the manual and made the requested voltage checks. I made all the measurements using two different meters just in case one meter was bad. The only one that was way off was D9 the expected measurement was 2.0 VDC and I measured .010 VDC. I started to think that Q7 and or Q8 were bad because I did not get the proper measurements when checking the transistors. But WA7SPY had a spare set and we tested those and got similar readings. I then started looking through the scamatics and tested the transmit voltage measurements for Q5, Q6 and Q10 as listed in the DC voltage tables. The following resulted: Q5 : B = 1.1 VDC expected 1.3 VDC, C = 12.6 VDC expected 12.4 VDC, E = .515 VDC expected .6 VDC Q6 : B = .6 VDC expected 1.1 VDC, C = 13.4 VDC expected 13.3 VDC, E = 220.1 mV DC expected .4 VDC Q10 : D = 1.57 VDC expected 1.6 VDC, G = 7.4 VDC expected 8.1 VDC, S = .95 VDC expected 1.6 VDC In summary it appears that I have good voltages from Q5 B,C,E and good voltages at Q10 D,G, and S but the base and emitter from Q6 are way down from the expected voltages. I have checked the winding counts for T1 and T2 and they seem to be wound correct. I checked to see if I had an open through T1 or T1 but they seem good. Does anybody have any suggestions where I should go from here? Am I even on the correct path? Any help would be greatly appreciated. Thanks David Davis, KG6MTI david-davis at att.net ------org 2 From: david-davis at att.net To: w7qhd at webtv.net (Kurt Cramer) Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] 40 Meter Transmitter Alignment problems Date: Wed, 01 Jan 2003 22:26:10 +0000 Kurt and All: I should have included this in the first email. When I test the voltages on transmit at Q7 and Q8 here are the results. Measured voltages for Q7 are: B = .638 VDC, C = -44.6 mVDC, E = 0.1 mVDC. Expected voltages for Q7 are: B = .6 VDC, C = 13.4 VDC, E = 0 VDC. ------------------------------------------------- Measured voltages for Q8: B = .636 VDC, C = -46.2 mVDC, E = 0.1 mVDC. Expected voltages for Q8 are: B = .6 VDC, C = 13.4 VDC, E = 0 VDC. As you can see the voltages to the collector on both Q7 and Q8 are not only the wrong polarity but way off. Would this represent a short to ground somewhere? Any suggestions? Thanks David, KG6MTI > David, set the current limit to 4 or 5 amps and try it. > > 73, Kurt > W7QHD (since 1951) > web page: http://W7QHD.tripod.com ------- org 3 From: "Bob - AG5Q" To: Subject: Re: [Elecraft] 40 Meter Transmitter Alignment problems Date: Wed, 1 Jan 2003 17:32:59 -0600 Hi David, The voltages at the base and emitter of Q6 are inconsistent. Since the emitter goes to ground through a small resistor, R50, the base must be about 0.7 V more positive to turn Q6 on. This inconsistency may be caused by the voltmeter probe affecting the operation of Q50, so when you measure the base you see one thing and when you measure the emitter, the operation is different so the two values don't seem to jibe. It might also be caused by the RF signal affecting the input circuitry of your meter, which expects a DC input. Rectification inside the meter can cause incorrect readings. Take a 1/4W resistor in the range of 10K to 20K (the value is not critical). Wrap one lead of the resistor tightly around the voltmeter probe tip and trim the other end of the resistor to about 1/2 inch long. This isolates the stray capacity of the voltmeter from the point you're measuring. Probe the base and emitter of Q6 with the resistor lead and see if the readings are different from before. The very low voltages at the collectors of Q7 and Q8 may indicate a problem in the T3 circuit. Trace the voltage from the point where +12V enters the circuit (in the vicinity of RFC4), through all the pads that the windings of T3 connect to to see where the +12 gets lost. Always use the isolation resistor with your voltmeter when measuring points where there may be an RF signal. 73/ Bob - AG5Q +++++++++++++++++ From: "Don Brown" To: "Gil Stacy" , Subject: Re: [Elecraft] 40M Tx Alignment Hi Current Concerns Date: Sun, 12 Jan 2003 14:23:48 -0600 Hi Sounds like your power supply is dropping out. With the supply voltage down to 10.8 volts the current will be high. The power supply should be steady at 13.8 to 14 volts. Some of the basic power supplies do not regulate very well. Another problem could be voltage drop in the power cable. Check the power supply with a voltmeter at the supply terminals and hit tune. The supply voltage should not change. The supply cable needs to be 18 or 20 gage wire to keep the drop down. Don Brown KD5NDB ----- Original Message ----- From: "Gil Stacy" To: Sent: Sunday, January 12, 2003 1:40 PM Subject: [Elecraft] 40M Tx Alignment Hi Current Concerns > > > > I am attempting the 40M Transmitter alignment in K2 #3104 and have high current concerns. With the power dial set at 2.0 watts, in TUNE mode, I peaked L1 and L2 to 3.6 a max of 3.6 watts. > I set the power dial to 5 watts, entered TUNE mode, and had a voltage drop from 11.7 V to 10.8 with a current drain increase from .22 to 2.14 amps. Recommended amps in TUNE mode are 1.3-1.6 amps. > At 10 watts in TUNE mode, the voltage drop is 1 volt with a current drain from .22 to 2.5 amps. Reommended amps in TUNE mode are 1.8-2.0 amps. > Voltage checks, recommended value in parenthesis where differs from actual reading. > Q6 B ok, C 10.8 (13.3), E .27 (.4) > Q7 B ok, C 11.16 (13.4), E ok > Q10 S 1.5 (1.6), G ok, D 1.5 (1.6) > Q11 all ok > > Q13 E ok, B ok, C 6.1 (7.5) > Q20 S ok, G ok, D 31mv (0.0) > Q24 G ok, S .81 (1.2), D .87 (1.3) > U9 1 ok, 2 4.8 (6.9), 3 5.02 (6.9), 4 31mv (0.0), 5 35mv (0.0) , 6 5.3 (6.9), 7 10.5 (13.8) > U10 ok > Q5 is untested as I have not pulled off the heat sink.Comments and suggestions would be appreciated. Thanks. > Gil KG4VCG +++++++++++++++++ Date: Sun, 26 Jan 2003 17:18:28 +0000 To: elecraft at mailman.qth.net From: Trevor Day Reply-To: Trev at secornwall.com Subject: Re: [Elecraft] TX/RX Discrepancy Hi All, Just to let you know that I have eventually found the fault which was causing my frequency difference problems and problems with CAL FIL. The fault eventually turned out to be a defective J310 FET at Q24. It was allowing a couple of volts to appear at its gate when in Tx mode which was sufficient to alter the bias on D37 and shift the BFO when transmitting. For reasons I don't understand (as I am not familiar with the way the firmware works) this also had an effect upon the audio response when in/out of CAL FIL. In any event, not having a J310 to hand I replaced it with a 2N3819 and all my problems disappeared! Hopefully the next fault won't be as elusive :-) 73 Trev G3ZYY In message , Trevor Day writes > >Hi Francis, >Its the latter; the settings set by CAL FIL remain and if I make a >change, exit CAL FIL and then return, the settings are as I had left >them. > >The problem is that the filter performance set (and seen with >spectrogram) when in CAL FIL, change when I exit CAL FIL. The audio >pitch also changes confirming the different filter response. But, when >I re-enable CAL FIL, the pitch changes back and the settings are where >I left them! > >I am convinced that this has something to do with the Tx/Rx difference, >but haven't found what is causing it yet. The problem lies on the RF >Board. I have exchanged everything else with parts from my working >unit. > >Thanks, >Trev G3ZYY +++++++++++++++++ Date: Mon, 17 Feb 2003 11:16:02 +0100 (MET) From: Frank Jonischkies To: elecraft at mailman.qth.net Subject: Fwd: RE: [Elecraft] K2 can't reduce power Paul answerd to my question, but only to me, not to the group. Thanks Paul. I will check the FET Q3 and Q4. I detected a blown FET Q5 (sidetone) on the Control Board. May be this was not the only one. Regards Frank, DH8JF --- Weitergeleitete Nachricht / Forwarded Message --- Date: Mon, 17 Feb 2003 09:36:27 -0000 From: "Fletcher, Paul" To: 'Frank Jonischkies' Subject: RE: [Elecraft] K2 can't reduce power > Frank, > > I had exactly the same problem when building my K2. In my case the problem > was caused by the T/R switching (blown FET on the control board) but this > can also be caused by an open circuit RFC in the PA stage (RFC16 I seem to > remember - but someone will correct me if I'm wrong) check the 8R and 8T > voltages to make sure they are switching - 8R must be close to 0V during > transmit and if it isn't that's your problem. > > Hope this helps. > > Regards, > Paul (M3BNF) > > -----Original Message----- > From: Frank Jonischkies [mailto:fjonisch at gmx.de] > Sent: 17 February 2003 01:26 > To: elecraft at mailman.qth.net > Subject: [Elecraft] K2 can't reduce power > > > Hello, > > I finished assembling K2#3227 and run the first transmitter test. When I > press tune (or keying the rig) the display shows HiCurr and an external > power meter with dummy load shows nearly 16 watts. I resoldered all > junctions in the amplifier. I did the receiver trace, all in the range. I > can't measure any values in transmit mode because the transmit is switched > off immediately. Looks like the ALC is not working. Which parts I have to > check? Any hints? +++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'David Walker'" , Subject: RE: [Elecraft] Resistor Pack Broken.... Date: Sun, 2 Mar 2003 18:24:22 -0800 Yep. It's a 470 ohm resistor across pins 5 and 6. Ron AC7AC K2 # 1289 -----Original Message----- ... I have a broken resistor pack.... Its the red coloured RP5, 470, 10pins (10A3.471G) part on the control board. It's broken between pins5 and 6. It's in two pieces. Does anyone know whether there is any connection between pins 5 and 6? I've emailed parts at elecraft for a replacement. Cheers, Dave. ++++++++++++++++++++ From: "Bob - AG5Q" To: "Elecraft Reflector" Subject: Re: [Elecraft] Q22 post mixer amp problems Date: Mon, 5 May 2003 12:19:26 -0500 I also found that my K2 had very low gain at first. I could barely hear only a few signals. Finally, using DC voltage measurements, I found that Q22 wasn't conducting any current. Even though the solder joint on the emitter lead looked good with a 3x magnifier, it wasn't. After resoldering the emitter, everything worked fine. Several people have reported a problem with Q22. I wonder if there might be a film on the leads? 73/ Bob - AG5Q ----- Original Message ----- From: "Wallace, Andy" To: "Ken Wagner" ; "Elecraft Reflector" Sent: Monday, May 05, 2003 8:14 AM Subject: [Elecraft] Q22 post mixer amp problems > -----Original Message----- > From: Ken Wagner [mailto:kewagner at ids.net] > > I noticed that the gain was *way* down and > that the Rx current draw was now 480ma. It smelled kinda hot as well. > Sometimes prior problems are helpful. On an earlier K2, I had > a problem with > the Post-mixer Amp circuit and this was > producing somewhat the same > symptoms, except for the increased current draw. > I removed Q22 figuring I would have to replace it. > I checked Q22 with a meter and it seemed OK. I put it > back in. Now it works just fine, thank you. I could spend hours > speculating what was wrong, but I won't. It works fine now. I find this _extremely_ interesting - can you tell me what you found on the previous rig, as well? When I built my K2 (#31xx) a few months back, I had problems in the exact same area. Resoldering Q22, RFC(16?) and a nearby cap brought it to life. (Unfortunately I didn't try one at a time.) The symptom was that the rig was fairly deaf; no abnormal current draw but to get S-9 with the preamp off I had to inject about 350 uV at the antenna jack! After resoldering, measurements very closely matched those in the ARRL K2 review. Been fine since. I did rewind the RFC and replaced the cap just in case, but left Q22 in. So this is interesting - wonder if something is up with the batch of Q22s in stock? Andy ++++++++++++++++ From: "Jerry T Dowell" To: Date: Mon, 5 May 2003 16:54:20 -0700 Subject: [Elecraft] Re: Q22 post mixer amp problems The usual problem here is using a little too much solder when installing Q22. As the solder flows through the hole, it can short the lead to the transistor can on the transistor side of the board. It is impossible to detect visually and very easy to do since the clearances are small. When installing Q22, use a minimum of solder and do it quickly. I had that problem when I first built my K2. It is easy to fix....just desolder the transistor, clean up any excess solder, and try again! 73, Jerry AI6L ++++++++++++++++ Date: Sat, 17 May 2003 12:06:36 -0700 To: elecraft at mailman.qth.net From: Jeff McLeman Subject: Re: [Elecraft] Weirdness on K2 tuning now Ok, with the help of Ron N9RC, I found the problem. Apparently, for a year now, pin 16 on U4 on the RF board was badly soldered. It worked at first, but when I was futzing with the A to B upgrade apparently I "jar'd" it loose. When I put the Thermistor upgrade in, it got even worse. Ron said look the bottom mounted resistors. So while i was perusing with the magnifier, pin 16 came into view. It looked horrible. I re-flowed, and viola! The chirping went away. Re-ran PLL cal, yet again, and now the rig is working fine. it is amazing how it worked this long :) Thanks to Ron, N9RC for just the moral support an to others that have responded. Again, this reflector is awesome. 72 de Jeff W7TTR -- ------------------------------------------------ Jeff -- W7TTR w7ttr at arrl.net Issaquah, Wa. ++++++++++++++++ Date: Tue, 20 May 2003 19:10:54 +1200 From: Ron W To: Elecraft Reflector Subject: [Elecraft] Fw: Strange loss of output... Hi again, I will be able to answer my own problem it appears...I took the set apart and checked the soldering on the toroids in the 20/30 BP and LP sections (even took them out to check the tinning). No problems there, so I resoldered all connections in the immediate area. Put it all back together. Still the same. ie. only 5w max out on 20m. Remembering past messages about variable trimmers and "seating" them I tried spinning the trimmers a few times, had another go at tuning the filters and it worked. I now have much the same output on all bands. I just have to hope it doesn't change again, but if it does I know where to look. Cheers.....Ron ZL1TW > Hi all, > I wonder if anyone can suggest what might be wrong here.....here is > the scenario: > For a while now the power out on 20m has been low. Today I can max about 35 > watts, so I took the long suffering K2 apart and went through the transmit > alignment again, put it all together. No change. > I then removed the KPA100 completely, powered the set from the old "QRP" > jack and looked again. > I can set the L8 and L9 for max power output on both 20 and 30m as > described. No problem there. I then peak C21 and C 23 for max power . Once > again no problem. > I can up the power to 5 watts and all bands show the same output on the watt > meter. > I set the power level to 10 watts and all bands show 10 watts (near enough) > *EXCEPT* for 20m which still shows 5 watts. I just can't get 20m to give > any output above 5 watts. > I guess a problem like this reeks of dud soldering on a toroid (?) , but > if > 30m ,( which shares the LP and BP filters) is fine , then where? > Having posted this I will go over the connections of the BP and LP > filters, > ....and that means taking off that gosh-awful heatsink panel > > Any ideas appreciated in the meantime. > Cheers......Ron ZL1TW > +++++++++++++++++ From: "Brian Wruble" To: "'Brian Wruble'" , Subject: RE: [Elecraft] possible K2 T/R Problem? Date: Sat, 24 May 2003 09:02:02 -0400 FYI: This turned out to be a defective Q4 on the control board. I replaced that, and everything checks out. 73 de Brian W3BW -----Original Message----- From: elecraft-admin at mailman.qth.net [mailto:elecraft-admin at mailman.qth.net] On Behalf Of Brian Wruble Sent: Saturday, May 17, 2003 6:00 PM To: Elecraft at mailman.qth.net Subject: [Elecraft] possible K2 T/R Problem? Hi Guys: I am in the Alignment and Test Part II Section of my K2 construction. Everything has gone beautifully to this point. I now have my first problem. I am in the section for the BFO alignment. When I first turn the K2 on, there is no audio. I can then get the audio to appear if I briefly key the rig. If I give it a "dit", I get audio. HOWEVER, if I move the VFO knob or move the RIT, or push any of the buttons, the audio disappears, and the S meter goes to full scale. Another "dit" brings it back. Doing voltage checks suggests a possible T/R switching problem. The 8R voltage on the RF board (at D6 anode) is only 0.6v when the rig is first turned on. When I give it a 'dit", I get audio, and that voltage goes to 8.3V. All of the RF Board switching diodes, D1-D7 have low voltages (0-0.6v) on turn-on, jumping to the correct voltages, per the RF Board voltage chart, after I give it a "dit". On the Control Board, Q1 and Q3 have the correct voltages, per the Control Board voltage chart. But, Q2 and Q4 do not. Q4 has voltages of S=0 (vs. 0 in chart), G=0 (vs. 5.0 in chart) and D=8 (vs. 0 on chart) on turn-on, and S=0, G=1.3 and D=0 after a "dit". Q2 voltages are E=8.5 (vs. 8 in chart) B=8.2 (vs. 7.3 in chart) and C = 0.8 (vs. 7.5 in chart) upon turn-on. After a "dit", these are 8.5, 7.6 and 8.4. Though I am not exactly sure what the "mute" function is, I think it may be the way the K2 tells the audio to go mute when various controls are pushed. Since this problem occurs when buttons are pushed, or the VFO moved, my natural assumption was that the mute circuit could be the problem. However, the /Mute (Mute=not ?) voltage is 3.85v. and does not change with the comings and goings of my audio. That voltage compares with 2.7* in the chart, with the asterisk indicating "approximate". Is 3.85V close enough to 2.7v? Q23 on the RF board, according to the manual, "is used to guarantee that 8R goes to 0V on receive to maintain proper reverse voltage on T-R switch diodes." (Found in "Theory of Operation", under "Control Board".) Can this possibly be a typo? I would assume 8R would be at 8V on receive, and would be pulled to 0v. on transmit. In any event, Q23 only has the correct voltages, per the voltage chart, when I have the audio. When first turned on (no audio), these voltages are S=0, G=0.37, D=0.82. These become 0,0, and 8 after a "dit", nominal readings based on the RF Board voltage chart. I have visually inspected, looked for cold-solder joints or shorts, reheated any suspicious joints, etc. Nothing seems to work. I am beginning to suspect component failure, possibly Q2, or Q4 on the Control Board, or Q23 on the RF Board. I would really appreciate any suggestions, ideas, etc. This is a basic K2, S/N 2528, with no upgrades as yet. Tnx for any help. 73 de Brian W3BW +++++++++++++++++ Date: Mon, 2 Jun 2003 14:54:32 GMT To: elecraft at mailman.qth.net From: wo7t at juno.com Subject: [Elecraft] VCO voltages only in range on 80 & 40.....Others > 8.0V K2 Builiders: I previously requested help with VCO voltage issues. For whatever reason, I had stuffed a cap into C76. How I arrived at a value is unknown, as my manual never provided for a C76 to be installed. I removed C76, and all VCO voltages now dial into range. 80-10M. Post resolution, I see this on Elecraft troubleshooting site. On to transmitter check-out now. 72, Mark K2 - #1051 +++++++++++++++++ Date: Mon, 02 Jun 2003 13:22:31 -0400 To: elecraft at mailman.qth.net From: Andrew Moore Subject: [Elecraft] 40m low sig: problem solved Thanks for all the responses to my troubleshooting questions. Further tracing brought me to C6 (4.7 pF) at the back edge of the board, which the manual states should be installed across the two outer pins of the three-pin jumper block. I interpreted "two outer" to mean the two adjacent pins near the "outer" side of the board edge -- i.e. in the direction of the side panel instead of the center of the edge. 40 meters is incredibly noisy at my location right now, so I still hear no signals, but the noise level has com'll assume I'm in good shape now -- will listen to some real signals tonight. I've never been so happy to hear noise on the band! Thanks N0SS for the terrific lesson in quick and dirty signal tracing. --Andrew, NV1B CFO 963 +++++++++++++++++