Sanjin, You may have some problem with the K2 VRFDET circuit - make certain the power displayed by the K2 during a TUNE is close to the actual power being developed. Do that both with the base K2 (no KPA100 physically attached), and with the KPA100 attached. If the actual power from the KPA100 does not match the power displayed, you should balance and calibrate the wattmeter in the KPA100.
Given that your symptoms indicate that there is too much audio drive to the KSB2 board, and also the fact that you bought this K2 used, look carefully for something like a microphone preamplifier in the K2. One easy way to tell if there is anything in the mic input path is to check continuity between the AF Pin on the mic connector (pin 1 for Elecraft microphones) and pin 5 of P1 on top of the KSB2 board. If there is not direct continuity there, someone has put something in the path. Also check the value of R14 (1k) and R15 (180 ohms) on the bottom of the KSB2 board. Stretching my mind for some other things - Do you have some source of low frequency rumble in your hamshack? That low frequency audio could be picked up by the microphone, and overwhelm the audio input. You might change C34 to 0.47 uF and C32 to a capacitor in the 0.0033 to 0.005 uF range to reduce the low frequency audio. Many have made that change and are quite pleased with it (I am one of those). With the KPA100 attached, how long does it take the power to settle down to 20 watts during a TUNE. It should take 30 seconds to a minute. If it settles faster than that, look on the bottom of the RF Board for the values of R98 and R99. If vastly different than the standard 270 ohms, change them back until you have this problem under control. You may want to optimize the value later after this problem is solved. (these resistors normally have nothing to do with your problem, but if they are way off the optimum value for your K2, strange things can happen). I certainly wish you had an oscilloscope. Is there any chance that you can borrow one? 73, Don W3FPR Sanjin Tajic, E71DX wrote: > Hello Don, hello Peter, > > I tried the mod suggested by Peter but it did not really help. It seems to > me that the ALC action is now somewhat better without the KPA100 attached > but I am still not really sure about that - will check again. > > Don do you have any other suggestions what I could try to do? > > Thanks for the help, > > Sanjin > E71DX > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
