Hi John, My power dances all over the place (my serial number is 00069). Just had a quick QSO with the KPA500 indicating 560 watts at the beginning and then going down to 480 at the end. That is typical. My 12 volt supply drops to 12.2 on transmit, 13.3 on receive. I have a long 12 volt cable from the supply so “I" squared losses are understandable in the cable. Driving power from the K3 is variable per band but typically set to 25 watts or so. The QSO described above was on 17 Meters and the drive is 25 watts there for ~500 watts out or just below after stabilization.
I remember the power fluctuation issue being discussed years ago on this reflector and it was explained that the power control uses a sampling and feedback loop that takes “time” to stabilize. That said, I believe we are both experiencing some power fluctuation over 10% in a short period of time. Depending on the amplifiers we are using this could cause real downstream issues, like distorted signals, spurs or alarm faulting of smart amplifiers. Could we have some aging component that is aggravating this issue? Our K3’s are among the oldest on the air. 73, Bill-AK5X > On Feb 29, 2016, at 2:24 PM, John K1JD <johnk...@comcast.net> wrote: > > Hi All, > My K3 SN #071 was purchased new November 2007. It’s had a few mods/upgrades > along the way and its firmware is current. > > Last Field Day 2015 at W5YA, the K3’s LPA failed after a close lightning > strike. I was able to successfully repair the LPA replacing both discrete and > SMD components. Performed a Pout calibration using the K3 Utility program > afterward and it passed. > > My 9500 amplifier (driven by the K3) has had a few instances of a high plate > current faults since new in December 2010. These faults had been infrequent > enough to ignore. More recently though the problems have been occurring more > often. Swapping the tube did not help nor did careful inspection inside the > amplifier reveal anything. > > Evidence that the problem is related to the K3 and not the amplifier > presented itself by accident a few days ago. I had the K3’s output set to 40w > and the Alpha was off. I inadvertently bumped the key and noted an > instantaneous output of 54w on the Powermaster II wattmeter. A few more dits, > and the power output settled back to 40w. Hmmm… if the amplifier had been in > line, the K3’s drive set for full legal limit and a first dit resulted in an > additional 30% drive, a high plate current fault might certainly happen. > > This morning I was using the KPA500 amp with my K3’s power set to 28 watts. > After an early AM CW fix I left the station on, walked away and came back in > a few hours hours. On first dit the KPA’s instantaneous power showed 650w on > the Powermaster II and illuminated a red LED on the KPA500, then settled back > down to <500w. > > OK, so it IS the K3 causing the problem BUT the power output spikes occur > very infrequently. It’s difficult to nail down the cause or even the > conditions under which the problem is most likely to occur. > > Reading the archives, others have had power spike issues over the years. Is > there a known fix? I’ve looked briefly at Elecraft’s alerts and mods but > nothing jumps out. > > 73, > John K1JD > Santa Fe, NM > > > > > ______________________________________________________________ > 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 wham...@aol.com ______________________________________________________________ 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
