[time-nuts] About HP10544A

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Mar 7 16:51:46 EST 2009


It was always intended for factory repair only so a service manual may
not be readily available.
The schematic is comprehensive enough that one hardly needs one.
The tricky part is setting the oven temperature.
There's probably a description in the relevant HP Journal (probably
early 70's).

Bruce

J. L. Trantham wrote:
> I have been able to find schematics of the 10544A but not a service manual.
> Is there a service manual available?
>
> Joe
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Bruce Griffiths
> Sent: Saturday, March 07, 2009 3:24 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] About HP10544A
>
> Esa Heikkinen wrote:
>   
>>> New 10544A's have a somewhat cleaner output than that.
>>> Perhaps something is wrong with the emitter follower.
>>>
>>>       
>> Sorry I forgot to say that the oscilloscope picture was taken directly
>> from HP10544A output, without emitter follower but with 1:1 probe,
>> output terminated with 1 kohm. resistor. With spectrum analyzer the
>> emitter follower is necessary due to 50 ohm. input impedance of the
>> analyzer.
>>
>> Datasheet of HP10544A claims that harmonics should be more than 25 dB
>> down. Doesn't look like they are.
>>
>> Here's a spectrum measured from OCXO which is used in the Thunderbolt.
>> I'm not an crystal oscillator guru but I think that this is just what an
>> xtal oscillator output should be:
>>
>> http://www.amigazone.fi/files/gpsdo/tbolt-1.png
>> http://www.amigazone.fi/files/gpsdo/tbolt-2.png
>>
>>
>>     
> Esa
>
> The capacitance of the 1x probe is too high.
> Use a 10x probe with 1k across its inputs at the 10544A.
> The 10544A output stage is an emitter follower.
>
> Bruce
>
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