Wow, Pete, what a puzzle! You might make up a little probe consisting of a wire connected to your rx antenna input that you can touch to the circuit parts. If it has to be a long lead, use a bit of coax so random signal pickup won't confuse things. If your rx input is grounded for d-c, put a small cap in series - anything from .001 to .1 should be FB - to provide d-c isolation. Then touch it to the collector of Q1. You should find your S-9 signal. If not remove coupling cap C4 and try again.
If you now have signal, there's a ground somewhere in the attenuator that is killing the signal. If not, you have a defective transistor (although that is high unlikely given that you've established that the voltage on the collector is correct.) Once you have the signal at the collector, start working through the attenuator until you lose it. Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pete Smith Sent: Thursday, January 29, 2009 3:15 AM To: [email protected] Subject: Re: [Elecraft] Need Help with XG1 Thanks Don. Unfortunately, all those variables test OK. I've gotta fix my old scope! I think that voltage must be an indication that the transistor oscillator is at least drawing the right amount of current through R9. I'm going back to recheck all my work on the default output attenuator. Must be something there, particularly since the additional stage of attenuation when I switch in the 1 Uv position seems to be working properly. 73, Pete At 02:30 PM 1/28/2009, Don wrote: >Pete, > >Do you have the proper voltage on Q1? Check for 1.22 volts at the cathode >of U2. Also check the value of R3 and R3 with your ohmmeter. > >It sounds like you have replaced everything important, but if you had >enough RF to fry the resistors, you may have damaged the switch contacts >at the same time. You should be able to determine the resistance through >the switch with your ohmmeter. Do that for both poles, and both switch >positions. > >73, >Don W3FPR > >Pete Smith wrote: >>Thanks for the idea - I removed both D1 and D2 from the circuit - no >>improvement. The signal is quite audible (in the 50 uv switch position, >>and barely audible in the 1 uV position, but doesn't move an S-meter that >>was formerly tested with it and registered S9. >> >>Anyone else? I know that if I had a scope I could measure the p-p >>voltage coming out of the oscillator, but I don't. >> >>73, Pete N4ZR >> _______________________________________________ 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 _______________________________________________ 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
