John, I believe after you replace diodes D16 and D17 in the KPA100 (both are 1N5711), you will find the problems go away. What appears to be happening is that they are not fully open nor shorted, but are at some state in between, so you do get some control, but it is just not right. Replace the diodes, then re-balance the wattmeter (adjust C1 with a non-metallic tool), and re-calibrate the forward power at about 80 watts into a dummy load.
You might just want to have 4 diodes on hand in case the two in the KAT100 have also been damaged. 73, Don W3FPR On 3/27/2011 4:30 PM, Jon Perelstein wrote: > Don, > > Thanks as always for your reply. > > But you don't seriously believe that my problems with electronic > equipment could be THAT simple, do you?? After all, I'm the guy whose > dog ate one of the ICs while I was building the K2 (no joke). > > I ran 5 watts and 2.5 watts, and ran each test five times (first 5, > then 2.5, then 5, then 2.5, etc.). > > With 5 watts commanded, both power meters usually read about 12 watts, > the K2's RF display read 5, and both the K2's ammeter and an external > WattsUp meter read about 2.7 amps. HOWEVER, on one try, both power > meters were indicating 15 watts (with about 2.8 amps on the ammeters > and 7 on the RF display). > > With 2.5 watts commanded, the MFJ consistently read 7 watts, and the > W1 consistently read between 6 and 8 (it doesn't have a display for > 7). The K2's RF display flickered between 2 and 3, and both the K2's > ammeter and the WattsUp read about 2.1 amps. > > You had me run this test sometime late last year because I was > reporting excessive heat when running in digital modes (e.g., PSK31). > At that time, the numbers were a lot closer to what was being > commanded -- although back then I was running it with the KPA100 in > use (trying 100 watts, 50 watts, and 25 watts). > > This started today because I was trying to tuck up the ribbon cable > and the speaker wire, which you had suggested to me a while back. I > hadn't actually tried that until today, and I noticed the power and > SWR problems after I buttoned everything back up and was testing the > change. I've put the ribbon cable and the speaker wire back where > they were to begin with, but am still having the power and SWR > problems, so my guess is that I managed to mess something up while I > had the case open, but I don't see anything offhand when looking at it > now. > > Jon ______________________________________________________________ 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
