------------------------ > > If you can see the 1 ohm or so difference that represents the resistance of > L6 when measuring from each end of it to ground, you can tell which side the > short is on without lifting one lead: it'll be on the end with the lower > resistance to ground. That will tell you whether to look in the direction of > T2 or toward Q7. > > The other possibility to a shorted Q7 is that Q7 is somehow locked "on". > There should be no bias to ground on the base of it to leave it off. If > there's about 0.6 VDC at the base then it's being held on by a current > through R2 that should not be there in receive mode. If that seems to be > case, grounding R2 at the end connected to the base of Q7 will turn it "off" > and make the short go away. > > Ron AC7AC
Looks like it's Q7. I pulled T2-2 and still had the short. So I pulled Q7. The short went away at L6 and the RX works. Q7 is shorted- only 3 ohms collector to emitter. I don't think it's not a random failure. The original problem with the KXB3080 was a hot Q6 but very low output power. That problem was caused by a solder bridge between B and A on the KXB3080 so I'll bet too much TX RF got into Q7 and fried it. If I'd caught the problem during RX testing I would have avoided this. At least I can play with the receiver while I wait for a new Q7. The sensitivity does seem improved, at least on 20 m, by the KXB3080. Thanks Ron, Don, and Alexandra, for all the help! 73, Bruce N7CEE _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
