Jon, Your quick tests are sufficient to negate my initial suspicion.
I would say your next step is to re-do the KPA100 bias adjustment. If you have the bias set too high, the PA transistors will heat more than normal. Meter the current into the KPA100 - put the K2 into CW test (hold the VOX button) and make sure the "C" indicator in the display is blinking - connect a dummy load to the KPA100 'just in case'. Set power to greater than 11 watts. The current draw will be in the vicinity of 500 ma. Whatever your external ammeter says, add 400 ma to that - this is your target value. The hold TUNE, and look at the ammeter - If it is a digital meter, wait until the 2nd reading (blink) because the first value shown may be too low due to the relative timing of the meter vs the time you pushed the TUNE button. The current will go up the longer you remain in TUNE, so obtain the reading and exit tune - adjust the KPA100 bias up or down a bit and try again. Once you have hit your target value, you are done - be sure to remove the ammeter from the power line. While you have the shield off the KPA100, you may want to check the balance on the wattmeter (C1 adjustment) and the power calibration with reference to a wattmeter that you are willing to trust. You should be ale to operate the KPA100 at 35 watts continuously without it getting too hot to touch - yes it will get quite warm, but not too hot to touch unless you have more sensitive fingers than average. RTTY can be considered continuous, PSK31 should be OK up to 50 watts since the PSK idle has a shorter duty cycle. If the bias and wattmeter are correct, and you still feel it is getting warmer than you would like, you might want to try a supplemental fan - find one from a defunct computer, and run it with a resistor in series to slow it down so the noise does not irritate. It can be placed on top of the heat sink, moving air away and will be quite effective. See Tom Hammond's website www.n0ss.net for his implementation. 73, Don W3FPR On 9/26/2010 6:49 PM, Jon Perelstein wrote: > Don > > Thanks for the quick reply. Fortunately, it appears that uncontrolled > power output is not the problem. > > And yes, it is a K2/100. > > I connected the rig to an MFJ-941E Versatuner II and connected the > Versatuner to my antenna. I tuned to a 1.1:1 SWR using the Versatuner > and then measured forward power on CW key down at various power > settings. The forward power transitioned smoothly from just under 20 > watts with the rig set to 20 watts to just over 90 watts with the rig > set to 100 watts. I probably need to do some calibration, but it > appears that the power control is working. > > I also tried it with PSK and Olivia transmissions and the Versatuner > was showing around 25 watts when I had 25 watts set on the K2's power > control. I upped the K2s power control to 40 watts and saw an > increase in forward power on the Versatuner to about 35 watts or so. > > I can get my hands on a real wattmeter in the next few days if you > think it necessary, but these tests would imply that I am not > experiencing uncontrolled power. > > Jon > KB1QBZ > > ______________________________________________________________ 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
