[time-nuts] HP 10544A with dodgy output?

Nick Foster bistromat at hotmail.com
Fri Jan 15 21:15:27 UTC 2010


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: bruce.griffiths at xtra.co.nz
> To: time-nuts at febo.com
> 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: jmfranke at cox.net
> >> 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: jmfranke at cox.net
> >> To: time-nuts at febo.com
> >> 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"<bistromat at hotmail.com>
> >> Sent: Friday, January 15, 2010 2:53 PM
> >> To:<time-nuts at febo.com>
> >> 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
> >>>
> >>> _________________________________________________________________
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> 
> 
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