> -----Original Message----- > From: [email protected] [mailto:[email protected]]On > Behalf Of J. L. Trantham > Sent: Friday, April 22, 2011 3:34 AM > To: 'Discussion of precise time and frequency measurement' > Subject: Re: [time-nuts] Fix Trimble Oscillator?? > > > John, > > Perhaps it is there and I did not see it, but do you have a > schematic of the > connections to the Trimble oscillator to go along with the picture? > > Thanks, > > Joe
There's not much to it -- just bypass both power pins near the point where they enter the can, and (if you want to do what I did) connect the wiper of a 10-turn trimpot to the tuning input. If you do that, and you want to drive the trimpot from the +12 supply, you need to use a resistor to limit the max voltage at the wiper to +5. Use a bypass capacitor where the resistor connects to the trimpot, and ground the 'cold' end of the potentiometer. For better stability, you should use an independently regulated supply to tune the oscillator, or at least don't drive it from the same supply wire that feeds the rest of the oscillator and oven. This unit was set up for short-term PN testing, so I didn't care about drift caused by slow changes in oven current. Another tip: even though they aren't really high-end Dewar-insulated parts, these types of oscillators are sometimes vacuum-sealed at the factory, and if you melt the solder at the seam, it will open up with a 'pop' and ruin the vacuum. So if you are making temporary solder connections like these for testing purposes, stay away from the seam. I don't know that this really hurts anything, but I imagine it could invalidate some thermal assumptions made at the factory. -- john, KE5FX _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
