> Do you have the serial number of your 10544? 1244A02119
> But this would depend on if the CA3045 were used in the oscillator. The CA3045 is only used on the buffer board. The oscillator uses several TO-5 transistors and a 2N3904. > Is the board shown actually the oscillator board or just the buffer board? That's the buffer + AGC board. > Is your OCXO a 10554 or is it a 10544A? Says 10544A on the case. Well, after disassembly, it turns out the problem was a bad solder joint on the oscillator return wire. Sometimes you just get lucky! Everything is locked on and working now. Thanks for everyone's help. Nick > Date: Sat, 16 Jan 2010 10:39:22 +1300 > From: [email protected] > To: [email protected] > Subject: Re: [time-nuts] HP 10544A with dodgy output? > > Nick > > The 10544A had at least 2 variants. > I have the originals but the various datasheets are available on Didiers > site. > The earlier versions had a somewhat higher phase noise spec, as can be > seen from the datasheets with different dates. > There was a significant change to the circuit to achieve the lower phase > noise. > > I don't have any details but I believe the changes were mainly to the > oscillator and the method of extracting the output signal from the > oscillator. > > I suspect that using 2N3904's rather than a CA3045 may lower the close > in phase noise. > But this would depend on if the CA3045 were used in the oscillator. > Do you have the serial number of your 10544? > > The circuit could be radically different as the CA3045 includes a > differential pair (the emitters of the pair are tied together). > From the image it appears that at least one of the transistors of the > differential pair is used in the circuit. > Is the board shown actually the oscillator board or just the buffer board? > > Is your OCXO a 10554 or is it a 10544A? > > Bruce > > Nick Foster wrote: > > Bruce, > > > > The 10544 I have doesn't correspond to the 10544 schematic I found on > > leapsecond.com. Here's a photo of the AGC board inside mine: > > > > http://www.nerdnetworks.org/~bistromath/photos/misc/10544.JPG > > > > It's an RCA CA3045 array instead of the 3094's used in the schematic I saw. > > Looks like the best thing to do is pull it out and test it, and replace if > > necessary. I imagine that despite the transistor change the schematic is > > mostly the same. Do you happen to know for sure? > > > > Thanks, > > Nick > > > > > >> Date: Sat, 16 Jan 2010 09:35:03 +1300 > >> From: [email protected] > >> To: [email protected] > >> Subject: Re: [time-nuts] HP 10544A with dodgy output? > >> > >> The output of the diode detector is compared with the dc base voltage of > >> the oscillator transistor adjusting the oscillator transitor current > >> whenever the detector output deviates from > >> Oscillator transistor base voltage - 2*Vbe. > >> > >> Bruce > >> > >> Nick Foster wrote: > >> > >>> Thanks for the quick reply, John. > >>> > >>> > >>> > >>>> From: [email protected] > >>>> Okay, 12V on the oscillator (pin 3) and 20V on the oven (pin 14). How > >>>> much > >>>> on the oven controller, pin 8? > >>>> > >>>> > >>> +12V. The oscillator uses the same supply as the filter, with the > >>> addition of a 10mH inductor + decoupling caps. > >>> > >>> > >>> > >>>> Are pins 2, 4, 5, 9, and 15 grounded? Pin 6 (EFC) should be grounded for > >>>> initial testing. > >>>> > >>>> > >>> Yes and yes. > >>> > >>> Upon looking further, something jumped out at me: the output is 2.2V RMS > >>> into 1000 ohms instead of the 1V RMS spec'ed in the datasheet. So I > >>> suppose the problem might be in the AGC circuitry, instead of the output > >>> emitter follower. It doesn't look as though the AGC in this oscillator > >>> contains a trimpot, like the 10811 does. > >>> > >>> I'm using the schematic at > >>> http://www.leapsecond.com/museum/10544/10544-3.gif, but I don't have a > >>> good idea of how that AGC works. > >>> > >>> --n > >>> > >>> > >>> > >>>> From: [email protected] > >>>> To: [email protected] > >>>> Date: Fri, 15 Jan 2010 15:06:42 -0500 > >>>> Subject: Re: [time-nuts] HP 10544A with dodgy output? > >>>> > >>>> Okay, 12V on the oscillator (pin 3) and 20V on the oven (pin 14). How > >>>> much > >>>> on the oven controller, pin 8? > >>>> Are pins 2, 4, 5, 9, and 15 grounded? Pin 6 (EFC) should be grounded for > >>>> initial testing. > >>>> > >>>> John WA4WDL > >>>> > >>>> -------------------------------------------------- > >>>> From: "Nick Foster"<[email protected]> > >>>> Sent: Friday, January 15, 2010 2:53 PM > >>>> To:<[email protected]> > >>>> Subject: [time-nuts] HP 10544A with dodgy output? > >>>> > >>>> > >>>> > >>>>> Hi all, > >>>>> > >>>>> I've just built a GPS-disciplined oscillator built around a 10544A, > >>>>> somewhat in the style of the Brooks Shera unit, just to use around the > >>>>> shack. Problem is, now that it's wired up, I notice the output is > >>>>> heavily > >>>>> distorted. It's clipped on the negative side of the waveform, like an > >>>>> emitter follower without enough headroom. The more I load the oscillator > >>>>> output, the heavier the clipping. When I load the oscillator output with > >>>>> 1000 ohms, spec for this unit, almost 30% of the waveform is clipped on > >>>>> the negative side. If I don't load it at all and just put a probe on the > >>>>> output, it looks OK, but still some flattening of the bottom half of the > >>>>> waveform. > >>>>> > >>>>> I've got it wired up according to the datasheet, with +12V on the > >>>>> oscillator and +20V on the heater. The grounds for the > >>>>> oscillator/amplifier, oven controller, heater, and output are all tied > >>>>> together. > >>>>> > >>>>> I know these are old units, and I'm wondering if this is a problem (for > >>>>> instance in the output emitter follower amp) that others know about, > >>>>> before I tear into it looking for a solution. > >>>>> > >>>>> Thanks for your time, > >>>>> Nick > >>>>> > >>>>> _________________________________________________________________ > >>>>> Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. > >>>>> http://clk.atdmt.com/GBL/go/196390709/direct/01/ > >>>>> _______________________________________________ > >>>>> 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. > >>>>> > >>>>> > >>>>> > >>>> _______________________________________________ > >>>> 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. > >>>> > >>>> > >>> > >>> _________________________________________________________________ > >>> Hotmail: Free, trusted and rich email service. > >>> http://clk.atdmt.com/GBL/go/196390708/direct/01/ > >>> _______________________________________________ > >>> 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. > >>> > >>> > >>> > >> > >> > >> _______________________________________________ > >> 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. > >> > > > > _________________________________________________________________ > > Hotmail: Free, trusted and rich email service. > > http://clk.atdmt.com/GBL/go/196390708/direct/01/ > > _______________________________________________ > > 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. > > > > > > > > _______________________________________________ > 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. _________________________________________________________________ Your E-mail and More On-the-Go. 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