Thank you all for the suggestions and encouragement. I am optimistic that it is now fixed. I believe it was one of the TMP coax plugs that had a faulty connection. But by shot gunning fixes I cannot pinpoint that specifically.
Below is the long story: Earlier I had replaced the wattmeter diodes, and it was suggested I do the wattmeter calibration. I had not been aware there was a WM calib, but it made sense since I had changed the diodes. So I did it. The LP calib was producing 4W on my wattmeter and I adjusted that parameter from 102 down to 070 to get 5W. HP was close to 50W but I tweaked it from 050 to 039 anyway. This made no difference in my transmit power problem. Tx gain calib passed at 5W but failed the 50W step with the power “not settling” “or converging to a consistent value and stopped at the 5.336 Mhz step. (Not a big surprise because I had noticed that when doing the wattmeter calibration, the power shown on my analog meter would slowly fluctuate, and later when trying a TUNE to 60W the K3 display would fluctuate erratically between 60 and 65. Didn’t think it should be doing that.)The 1 mW test had the same error wording. Learning about the wattmeter test showed there was a SYN calibration too, so I did it. This ran OK but made no change to the problem. Time to bite the bullet and start taking apart the radio to check connections, look for bad solder joints, burned parts, etc. Having no SMT rework tools, and imperfect eyesight, I would not attempt a fix but would cross that bridge later. So, on went the ESD strap, and the first step was to take off the top cover and remove the subreceiver, since it blocks the view and access of everything on top. It was easy to remove the sub-receiver, but I forgot how hard it is to install it- more on that later. In the process of removing the sub, many of the little coax cables get loosened, rotated, etc. The sub really crams these into tight spaces making it difficult to fiddle with them. Once the sub was out, I did remove, spray, wipe, and reinsert them solidly; plus I loosened the mounting screw of many of the PCBs and wiggled them about in their pin sockets. Wondering if perhaps the subreceiver was a contributor to the problem either with an internal fault or by inadvertently shorting something to its case, I powered up the radio, and to my delight, it now worked!!! Tune power would quickly reach the setpoint and stayed steady on all the band I tried. I ran the TX gain calibration routine, and it passed all!!! Next, I decided to do a better job with the PCB connectors by taking them completely off, checking them visually, spraying the pins and reinstalling them. That turned out to be an adventure with the boards that screw onto the metal front. Fat fingers make it hard to hold the tiny screws with a lock washer on the head and a split washer on the back, insert the board into the bottom connector, and not drop off the split washers. After many failed attempts, my solution was to put a tiny dab of dielectric grease on the screw threads sticking out the backside so that the split ring washer would not easily slide off. (On static contacts the actual contact areas are little high points that flatten a bit based on their hardness and the pressure on the contact surfaces. The actual contact area is a small fraction of the physical contact surface. Any grease is punched through and squeezed out from under them so is not a problem.) I also removed and replaced the front panel in a similar manner. It is easy to take off and put back on. I then decided to wait a few days before going further. Throughout the day I would do a TUNE and found the output power quickly reached the setpoint and was stable. With my dummy load, the K3 SWR readings came out to be 1.0 on all bands except 40M where it was 1.3. I took off the bottom plate and reflowed a few of the thru holes and then wiggled 3 of the trimmer caps in the 40M section. I could not locate the 4th trimmer. This made no change to the 1.3 on 40M, and that remains a mystery. Eventually it was time to put back in the subreceiver and finish buttoning her up. It is not easy to put in the sub. I rerouted some of the little coaxes to minimize them pulling on each other or getting caught between other parts. With the subrx chassis in place there is scant room to ensure the TMPs are all in snug. This does suggest maybe the original problem had to do with a TMP connector strained, or partly pulled out from the original sub installation. It took a few hours until I could satisfactorily get it done. Before putting on the chassis stiffener and top cover, I again tested the radio. All was fine. The last thing I did was to return the power supply voltage down to 14.0 volts. I felt having it up at 14.6 from a previous attempt to solve the problem was too high to leave it. Again, all was fine and it breezed through another TX gain calib run. My sincere thanks to all those offering suggestions and relating their experiences. 73, Chet, N8RA ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
