Vic, I would think that is a possibility, but can't be certain at this time - did you change R19 and R20 when you added the upgade? If not, please change them and see if that fixes it. With care, you can change the resistors from the top of the board.
>From what I can recall, slightly higher value capacitors will only cause a bit of a power output dropoff on the high bands. I once had a KPA100 here that had severe power dropoff on 20 through 10 meters, and I overlooked C80 and C81 many times before discovering that they were .047 uF instead of the 4700 pf, so I know the amp will 'work' with much higher value capacitors. BUT if you have the inductive resistors (the real problem behind the temporary change to the 5600 pf caps), then they could be the cause of your current problem. I have 4 KPA100s to upgrade here, and one of them may have the 5600 pf caps installed - yet to be checked, let's hope I am lucky enough to be able to verify the problem situation. 73, Don W3FPR > -----Original Message----- > > Don Wilhelm wrote: > > > Here is what happened on C80 and C81 - for a short time after > the 20 and 17 > > meter low power output problem, it was thought that the C80 and C81 > > capacitors had to be a higher value. Well as things turned out > the problem > > was really that the resistor manufacturer had changed R19 and > R20 (1.6 ohms) > > to an inductive design without notifying Elecraft. > > How well I know this! Without going into detail, I have 5600 pf > capacitors installed. Is this a possible cause of instability on 21 MHz.? > > I really don't want to take the board off the heatsink again unless I > know for sure that this is a likely cause of my problem. > -- > 73, > Vic, K2VCO > Fresno CA > http://www.qsl.net/k2vco > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
