Don - The PA’s have never seen any power nor have I tried to transmit yet. In the morning I’m going to take all the panels and boards off the RF board and see if I still pass all the resistance checks. I don’t understand how I can pass the resistance check and then see this behavior when the boards and panels are installed.
Mark W8EWH On Sat, Jan 4, 2020 at 10:28 PM Don Wilhelm <[email protected]> wrote: > Mark, > > The most usual cause of a Q7/Q8 short to ground is that the thermal > insulators are not installed properly. > However, your statement that you see the same with the heatsink off > indicates that the Q7 or Q8 transistors have been damaged by a collector > to emitter short. If the K2 was subjected to a transmit without the > heatsink installed, that could be reason for the demise of Q7/Q8 > transistors. > > Make certain that the PA mounting hardware is installed correctly, > especially the shoulder washers. > > 73, > Don W3FPR > > On 1/4/2020 9:11 PM, Mark Yergin wrote: > > I'm in the final stages of my K2 build, but having a problem with Q7 and > Q8 > > shorting to ground. When I did my Resistance Checks on pg 74, I had > 3.66K > > ohms to ground at the Q7 collector. So that was fine. But when I put > all > > the boards and panels on, then attached Q7 and Q8 to the heat sink, I see > > about 135 ohms between the Q7 and Q8 collectors and ground. I assume > > that's unacceptable. I see the same with the heat sink off. > Suggestions? > ______________________________________________________________ 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 Message delivered to [email protected]
