[time-nuts] HP 10544A with dodgy output?
phil
fortime at bellsouth.net
Fri Jan 15 21:53:05 UTC 2010
Didn't some of the 5345 or 5328 manuals have schematics for the 10544. I
have no idea if it's in the on-line manuals but I recall seeing the
timebases in some.
Phil
----- Original Message -----
From: "Bruce Griffiths" <bruce.griffiths at xtra.co.nz>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Friday, January 15, 2010 4:39 PM
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: 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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