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
