On Tue, 15 Aug 2006 08:53:22 -0400, "Don Wilhelm" <[EMAIL PROTECTED]> wrote :
> Pat, > > Something strange is happening here. First the facts of 'the case': > 1) The KPA100 wattmeter should not be frequency dependent, and neither > should your external wattmeter if it is functioning correctly. > 2) Your KPA100 wattmeter apparently needs to be calibrated - use a good 50 > ohm resistive dummy load and start over at the point where you adjust the > trimmer cap - caution, a dummy load that is reactive will give you an > incorrect indication of the null point. > 3) If you use your external wattmeter to set the KPA100 forward power level, > then the K2/100 indication should track with that external wattmeter > afterwards. > 4) Be aware that an external wattmeter may be in error by as much as 10 or > 20% OF THE FULL SCALE READING! This is the typical spec for wattmeters. Be > careful of the scale, on a 100 watt scale, that means that the error could > be as large as 20 watts (at any point on the scale), so do not use a 100 > watt scale to read a 20 watt level, use a 20 watt scale where the maximum > error is only 4 watts. I cannot stress this subtle point strongly enough. > Even a Bird wattmeter is speced at 5% of full scale, and that is only > guaranteed after calibration! > Don, I've done all this and taken it into account. I don't typically post unless I've spent several hours puzzling over a problem. > You may have something else wrong there too, but as first steps, check the > components in the wattmeter section and re-do the wattmeter calibration. > Then see if the power control becomes proper. > Here is what I think the problem is: U7 Pin 1 is listed as being between 0 and .8 volts on rx mine is 0 volts on transmit it is about whatever the supply voltage is, in this case 13.5v. Looking at the circuit, I see that it supplys voltage to Q5 and is part of the current sense. On transmit I measured zero volts on the emitter of Q5, TP1 and that end of R30. Seems like Q5 might be dead. I replaced Q5 and now U7 Pin 1 is about .5v on tx. However, U7 pin 7 is not right so guess Q4 might be suspect. Pat _______________________________________________ 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
