First thing I tried was that C119 cap on the board. Tweaked it just a little and the calibrator signal "popped in", nice and strong. Tried putting it back and it pretty much disappeared again. So I guess depending on environmental parameters it was at a marginal value for sustaining oscillation.
Thanks for all the pointers, Chuck, K1OM On Mon, Oct 25, 2010 at 5:42 PM, Chuck Grandgent <[email protected]> wrote: > Thanks Richard, thanks Garey, Lots of things to try and check, > will report back what I find after poking around. > > Chuck > > > On Mon, Oct 25, 2010 at 5:15 PM, Richard Knoppow > <[email protected]>wrote: > >> >> ----- Original Message ----- From: "Chuck Grandgent" <[email protected]> >> To: <[email protected]> >> Cc: "drakelist" <[email protected]> >> Sent: Monday, October 25, 2010 1:52 PM >> Subject: Re: [Drakelist] R4B erratic crystal calibrator >> >> >> Yes, C192 was also part of the Hayseed recapping. >>> >>> I will check D16. >>> >>> The erratic operation (better characterized as failing to stay in >>> oscillation) was there both before and after the recapping, with the same >>> modus operandi. >>> >>> I do also have a spare 100khz crystal, same form factor, I suppose I >>> could >>> try that too. >>> >>> Chuck, K1OM >>> >>> On Mon, Oct 25, 2010 at 4:37 PM, Garey Barrell <[email protected]> >>> wrote: >>> >>> Chuck - >>>> >>>> Does Tom's kit include C192? I think it does. If not .... >>>> >>>> Also D16. >>>> >>>> And with the erratic operation, solder joints on C190, etc. Tough >>>> places >>>> to solder. >>>> >>>> 73, Garey - K4OAH >>>> Glen Allen, VA >>>> >>>> Drake 2-B, 2-C/2-NT, 4-B, C-Line& >>>> TR-4/C Service Supplement CDs >>>> <www.k4oah.com> >>>> >>>> D-16, R-158, R-157 C192, C-190, all appear to be part of a low >> voltage supply that feeds the calirator and nothing else. Looking at the >> junction of C-190 and the emitter of Q-9 should tell if its working. This is >> a half-wave rectifier fed by the 12V filament supply with large filter caps >> so the DC out of it should be more than 6 or 7 volts, anyway, it should be >> there all the time. The calibrator is switched by lifting a ground at the >> source of TIS-34, the oscillator. Its possible the function switch is >> intermittant, maybe not likely but its worth cleaning the contacts on S-3 >> front. I don't remember if the transistors in this circuit are in sockets or >> soldered in, if in sockets wiggle them and if soldered it might be worth >> re-flowing the solder. Also, Garey often recommends working any screws that >> are used for grounding. This kind of intermittant sounds like a heat problem >> but even intermittant switches can be affected by heat. >> The output of the calibrator is available at the antenna input to the >> receiver and that is a convenient place to check for its presense and for >> adjusting the calibration. Also, work the calibrator adjusting capacitor. I >> think this is a very unlikely cause but won't hurt anything. >> >> >> -- >> Richard Knoppow >> Los Angeles >> WB6KBL >> [email protected] >> > >
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