Hi Don - OK, I have gone through the transmit signal tracing steps and found a couple of anomalies. I'm referencing the specific section name and step number in the troubleshooting here.
ALC: 3. Pin 2 of U8 (on the control board) shows 4.97VDC instead of the expected .7 - 2.5VDC. The manual tells me to check the component values in the RF detector, which I have. They are all correct. Transmit Mixer, Buffer, etc 2. Pin 4 of U10 shows .228 Vrms instead of the expected .016. 3. Pin 6 of U9 shows 1.148 Vrms instead of .2. 4. W6 shows 0. 5. D1 shows 0. So those seem _totally_ out of whack. These checks were done on 40m, which is where I'm having problems. Now what? -- [email protected] (Owen B. Mehegan) 'Nothing fixes a thing so intensely in the memory as the wish to forget it.' --Michel de Montaigne On Oct 5, 2010, at 11:33 PM, Don Wilhelm wrote: > Owen, > > You should not need a signal generator for Transmit Signal Tracing - > I believe you are in the Receive Signal Tracing area - skip that and > go to the Transmit Signal Tracing. The K2 itself is the signal > generator for this TX signal tracing. > > Try increasing the CAL CUR setting to 3.50 Amps rather than the > manual suggested setting of 2.50 amps. > Often the 80 meter output will be well above the 15 watt level, and > the current needed for that higher power output will be in excess of > the 2.50 Amp setting. > > If the Hi-Cur messages persist, then look to the Low Pass filter for > the answer to your problems. Count the turns on the toroids > carefully. A problem with Hi-Cur coupled with low power output is > normally an indication of a problem with either T4 or the Low Pass > filter. > > 73, > Don W3FPR > > On 10/6/2010 1:42 AM, Owen B. Mehegan wrote: >> Thanks again for the suggestions Don. Tonight I started doing some >> signal tracing, and my RF probe seems to work fine with my DMM. >> However, I ran up against a different obstacle: I don't have a signal >> generator handy, and the LPF/BPF/T-R Switch tests seem to require >> one. >> I can get access to one but it won't be until tomorrow at least. >> >> I did find one other data point for my symptoms. On SOME bands, I get >> the expected power out when I put the K2 into tune mode. Here are the >> results of my tests: >> >> 80m sometimes shows "high cur" the first time I test, then I quickly >> turn off tune, then try again and I see a normal reading >> 40m always too low >> 30m same as 80m >> 20m OK >> 17m OK >> 15m OK >> 12m too low >> 10m too low >> >> I checked continuity on all my toroids, from "pad to pad" instead of >> lead to lead, as far as I was able. Everything seems to check out >> there. I'm not sure I can do anything else without a signal >> generator, >> but I'm open to suggestions. >> >> -- >> [email protected] (Owen B. Mehegan) >> 'This above all: to thine own self be true, >> And it must follow, as the night the day, >> Thou canst not then be false to any man.' >> --William Shakespeare >> >> On Oct 5, 2010, at 7:01 AM, Don Wilhelm wrote: >> >>> Owen, >>> >>> I am going to assume that you were successful with the Alignmant and >>> Test Part II and were able to receive 40 meter signals. If not, you >>> need to backtrack a bit and get receive working first. >>> >>> The easiest way to troubleshoot a "lack of power output" problem is >>> to do Transmit Signal Tracing. You can use an RF Probe or an >>> oscilloscope with a 10X probe. >>> >>> Turn the manual to the Appendix E section titled Transmit Signal >>> Tracing and begin there. If using an RF Probe, the correct expected >>> values are listed, but if using an oscilloscope, multiply those >>> values by 2.8 and observe the peak to peak voltage of the RF >>> waveform. >>> >>> An important note - the K2 will normally increase drive in an >>> attempt to increase the power output if the voltage out of the RF >>> detector is too small. What that means is that all RF voltages >>> prior to the failing stage the RF voltages will be higher than the >>> listed expected values. You will be investigating the transmit >>> chain in the order listed (do not skip around), searching for the >>> *first* stage where the output is lower than expected - that is the >>> failing stage which then needs to be analyzed to determine why it is >>> not operating properly. Measurements beyond this first failure >>> point are not relevant to that first problem to be found. >>> All RF Voltage measurements in the list can be done from the top of >>> the RF Board. Do not transmit with the heat sink removed. If the >>> PA transistors do get a bit of drive, will produce output and if the >>> heat sink is not in place, they will quickly overheat and fry >>> themselves. >>> >>> Normal failures are soldering problems, toroid leads or incorrectly >>> placed components. Active device failures are way down of the list >>> of failure suspects unless something has caused it to be abused. >>> >>> 73, >>> Don W3FPR >>> >>> On 10/5/2010 2:38 AM, Owen B. Mehegan wrote: >>>> Hello - >>>> >>>> Two nights ago I completed the assembly of my K2's RF board, and >>>> after >>>> a visual inspection verification of resistance checks, I assembled >>>> the >>>> radio per the instructions and began the third phase of alignment >>>> and >>>> test. I've discovered a problem right off the bat, though. In the >>>> 40 >>>> meter transmitter alignment section, when I put the K2 into tune >>>> mode >>>> at 2 watts power, I'm only reading .3-.4 watts on the onboard >>>> wattmeter (it alternates between the two). This is with a >>>> connection >>>> to a 100W dummy load. Varying L1 and L2 has no effect on the power >>>> reading. >>>> >>>> I discovered one mistake: I misread the instructions for winding >>>> T4's >>>> 5-6 and 7-8 windings. I wound these bare wires through BOTH holes >>>> in >>>> the core, in a U shape, thus connecting 6-7 and 5-8 (and very >>>> possibly >>>> all 4 together with a short in the middle - this is what comes of >>>> staying up too late working on a project!). I corrected this >>>> mistake >>>> tonight, but I'm seeing no change on the measured power. Is it >>>> possible that this mistake fried something? I never saw any smoke >>>> or >>>> smelled burned silicon, and the thermal pads on Q7 and Q8 look >>>> normal. >>>> >>>> I have also noticed that if I vary the power adjustment on the >>>> front >>>> panel while in tune mode, I see no change on the wattmeter. That >>>> seems >>>> significant. >>>> >>>> These are the other checks I've done so far, per the >>>> troubleshooting >>>> instructions: >>>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
