Bill, You may use the 2SC1969 transistors you have, they should be just fine. Also replace Q11 and Q13.
The most likely thing that has happened is that the bias on the PA transistors increased - either because of a fault in Q11 or Q13 or because one of the PA transistors developed collector to base leakage which will drastically increase the bias current and destroy the PA transistors. 73, Don W3FPR Bill Miner wrote: > Hello Elecrafters, > > I recently finished construction of my first K2. > > I was very careful about ESD precautions during construction. While > performing the transmitter alignment it was never in transmit for more than > just a few seconds. The PA transistors and heat sink were all properly > installed. The rig had correct output power on all bands. It was being > operated from an Astron 4 amp supply with about 13.5 volts output.The > transmitter was terminated into a known good commercial quality 50 ohm load. > At no time did the heat sink get more than slightly warm. In other words the > PA transistors were not abused in any way. > > I have not yet even made the first QSO with this rig. This morning when I > turned it on to listen around the bands it came on for a few seconds and then > failed. > > Some clever and careful trouble shooting revealed that Q7 PA transistor is > shorted. > > I have some spare 2SC1969 transistors but they are from a different > manufacture. Should I use these or get new ones from Elecraft? According to > some previous posts there may be a problem with other transistor brands. > > Is this type of K2 failure common or just a fluke? I have never had any kind > of PA failure in any other rig that I have owned over the years. > > Thanks for any thoughts that you may want to pass along. > > 73, Bill - K6WLM > > > ______________________________________________________________ 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
