[time-nuts] HP 10544A Repair

Bob Camp kb8tq at n1k.org
Sat Feb 27 22:03:51 EST 2016


Hi

The key bit of missing info:

You likely have a BT cut crystal in that OCXO. If it was an AT, you wold look for a minimum frequency. With
the BT, you look for a maximum. 

Bob

> On Feb 27, 2016, at 9:48 PM, Nigel Vander Houwen <timenuts-nigelvh at nigelvh.com> wrote:
> 
> Hello All,
> 
> Relatively new to the group, but thought I’d ask for a bit of advice. I have an old HP 10544A ovenized oscillator that was pull from some equipment some time ago because it got too far off frequency to phase lock with the external reference. It looks like the thermistor in the oven controller failed, and just wouldn’t ever turn the oven on.
> 
> I’ve replaced the thermistor, and the oven is working properly again, but I need to tune the temperature as appropriate for this crystal. I’ve read that this involves plotting crystal frequency vs temperature, so I’ll need to adjust the potentiometer inside, close it up again, wait for temperature to stabilize, and take a frequency measurement, and iterate.
> 
> If I’ve understood what I’ve read correctly, I’m looking for a flat in the frequency response of the crystal with regards to temperature.
> 
> I do have a HP 5345A referenced from a thunderbolt to do the frequency measurement.
> 
> Am I on the right track? Further insights? Etc?
> 
> Thanks all!
> Nigel
> K7NVH
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