Ariel, You may indeed have a problem with D9 and the 3 associated resistors in the base K2, BUT when the KAT2 or the KPA100 is installed, that circuit is ignored. Both the KAT2 and the KPA100 contain a true wattmeter that is positioned right at the output and used for power control.
The K2 microprocessor reads the actual output and compares that to the power knob setting. That result tells the microprocessor how to adjust the drive. Unlike other ham transceivers, the K2 uses a closed loop to control the power instead of simply adjusting the drive. What that also means is that the wattmeter in the KPA100 is not working (you have shown that the one in the KAT2 is working OK). As I indicated before (and also indicated by your high SWR indication) there is a high probability that KPA100 diodes D16 and D17 have been damaged. When the diodes are damaged, the output back to the MCU is most likely zero, and the MCU *thinks* there is no power output - it then increases the drive to the maximum in an attempt to develop power. The result is a HiCur warning and stress on the base K2 PA transistors. Replace KPA100 D16 and D17 as the first order of business and after that you can investigate any remaining problems. Note that those diodes can be "half bad" and may show as good with a diode test - replacement is the first order of business. 73, Don W3FPR On 10/25/2012 11:31 PM, Ariel Jacala wrote: > Don > > The K2 with the ATU behaves as expected - internal meter agrees well with the > external meter, current draw is as expected, and so forth for various power > levels up to 10watts checked out. It was connected to a dummy load. > > Without the ATU and the dummy load connected to the base K2 antenna, things > are rather strange.... At 2 watts set on the power knob, output on the > external meter is 2.7 watts and current draw is 0.96 amps; at a knob setting > of 2.4 watts, output is up to 7 watts on the external meter and current draw > is 1.4 amps; at a knob setting of 2.5 watts, power output is 10 watts and > current draw is 1.96 amps; at 3 watts knob setting, I get the high current > warning, and the external meter is pegged. > > This leads me to believe that the base K2 is overdriving the KPA100. At low > power settings - 5 watts, I was pegging the LEDs indicating power on the > LDG100 autotuner, at over 125 watts. > > Ariel NY4G > > Sent from my iPad > > On Oct 25, 2012, at 11:51 AM, "Don Wilhelm" <w3...@embarqmail.com> wrote: > >> Ariel, >> >> Do not be too quick to conclude that there is something wrong with the base >> K2. The basic K2 uses only an RF voltage diode to display the power output, >> and it may not be exact - it depends on the load and may vary from band to >> band - if it only off by a watt or two, then all is OK That is bypassed >> when the KAT2 or KPA100 is installed. >> >> Yes, do check with the external wattmeter - both with and without the >> KPA100. I still think KPA100 diodes D16 and D17 are highest on the suspect >> list with other KPA100 wattmeter components being second on that list. >> >> 73, >> Don W3FPR >> >> On 10/25/2012 11:18 AM, Ariel Jacala wrote: >>> Thanks to Jim, Vic and Don for the return comments >>> >>> I disconnected the KPA100 and put on the K2 top with the KAT2 ATU. With >>> the K2 ATU connected and the dummy load connected - the SWR correctly reads >>> 1:1 with menu set for CALS. With the menu set to CALP, the power levels >>> appeared to modulate correctly with the PWR knob although this is an item i >>> have to double check. With the ATU disconnected, the displayed power on >>> tune differs from the power setting. This suggests to me that there is >>> something wrong with the base K2. I still have to do what Don suggested >>> about connection to an external watt meter. >>> > ______________________________________________________________ > 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 > ______________________________________________________________ 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
