[time-nuts] About HP10544A

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Mar 8 01:48:55 UTC 2009

Tom Van Baak wrote:
>> I have been able to find schematics of the 10544A but not a service manual.
>> Is there a service manual available?
> http://www.leapsecond.com/museum/10544/
> I'll look for something like a service manual. I know I have some
> interesting info in the 10544. When I find it I'll update the page.
> One thing you could do is look at hp op/service manuals of
> instruments (e.g., frequency counters) made in the late 70's
> and see how they integrated the 10544 into their design. This
> will give you hints on both input power and output buffering.
> I know *late* model 5245L counters used the 10544A oscillator.
> Perhaps others in the group can provide other examples and
> then you can head off to the online manual sites and grab the
> info you need from the PDF files.
> /tvb
Output buffering is easy, however the load capacitance seen by the
10544A must be kept below about 10pF to meet the distortion specifications.
This means the buffer needs to be very close to the 10544A output pin
unless one uses positive feedback or other techniques (eg shunt
inductor) to cancel excessive input capacitance.
The load impedance needs to be 1Kohm or higher at 10MHz, to avoid
excessive distortion on the negative portion of the 10MHz nominally
sinewave output.


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