Michael, If you have the new 2SC5739 transistor at Q6 (plastic tab), it will run hotter than the previous Q6 2SC2166 (metal tab) To tame it down, change R46 from 270 ohms to 330 ohms which will reduce the bias voltage during transmit. Q6 should cool down during receive.
OTOH, if you have the 2SC2166 installed or Q6 does not cool down during receive, that is an indication of a problem. Check the 8R and 8T voltages during both transmit and receive. You can measure those voltage rails easily at the anodes of D6 and D7. During receive D6 anode should be about 8 volts and D7 anode should be near zero. During transmit, the reverse should be true. If there is a problem, check Control Board Q1 and Q2 (the controlling source for these voltages) and RF Board Q23 which should pull 8R to almost zero during transmit. If Q6 stays hot during receive periods, that could indicate a shorted RF Board Q10. 73, Don W3FPR Michael van Hauten wrote: > Hi, > today i did a recalibration of my K2. I recognized, that Q6 became very hot > after a short time pressing TX at the mic in SSB mode, even without > modulation. All voltages at the related transistors are equal to the manual. > The current goes from 300mA in RX to 680mA in TX without mod. Any ideas? > vy 73, Michael, DC0ZO > > ______________________________________________________________ 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
