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

[Bruce Griffiths]

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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