[time-nuts] HP 10544A Repair

Glenn Little WB4UIV glennmaillist at bellsouth.net
Sun Feb 28 23:19:53 EST 2016


While in the navy, I had to repair a hp cesium standard.
The control circuit had the oscillator slewed to one limit, I do not 
remember whether high or low.
We had no spare parts to support this standard.
The only option was to run the standard open loop.
Over a period of two hours, I had the standard off for no more than 15 
minutes total.
To get the standard back on frequency, I had to compare this standard to 
the other standard using an oscilloscope to produce a Lissajous pattern.
I set the oscillator on frequency by stopping the rotation.
I checked it again in 6 hours and the pattern was fastly rotating.
I reset the frequency and checked it at 6 hour intervals.
It took two weeks for the oscillator to thermally stabilize after being 
off only 15 minutes.
Be prepared to have to wait to get the oscillator thermally stabilized.

I am not positive that this was a 10544A, but, it was a similar ovenized 
precision oscillator.


YMMV

73
Glenn
WB4UIV


On 2/28/2016 8:10 PM, Bob Camp wrote:
> Hi
>
> Except ….
>
> The big steps give you more “thermal shock” on a BT and that slows things down.
>
> Bob
>
>> On Feb 28, 2016, at 7:28 PM, Richard (Rick) Karlquist <richard at karlquist.com> wrote:
>>
>>
>>
>> On 2/28/2016 7:01 AM, Bob Camp wrote:
>>> Hi
>>>
>>> It’s not an electrical issue as much as a heat issue ….
>>>
>>> Before you start, consider that you will be doing something like:
>>>
>>> Move trimmer 1 turn CW
>>> Wait 10 minutes
>>> read frequency
>>> Move trimmer 1 turn CW
>>> wait / read
>>> Move trimer 1/2 turn CCW
>>> wait / read
>>> Move trimmer 1/4 turn CW
>>> wait / read
>>> Move trimmer 1/8 turn CCW
>>> wait / read
>>> Move trimmer 1/16 turn CW
>>> wait / read
>>> Move trimmer 1/32 turn CW
>>> wait / read
>>>
>>> That is indeed an ideal version. You likely will do multiple steps at each of the stages rather
>>> than get it right the first time. The part needs to be warmed up for a few days before you
>>> can get to the 1/32 turn level. You also need a good standard to compare to.
>>>
>>> Bob
>>>
>>
>> Instead of that, start with the pot at max temp, and have the counter make measurements at, say, 1 second intervals as the oven warms up.
>> You can tell by looking at the plot what the peak frequency is.  Now
>> that you know the peak frequency you are shooting for, it will take
>> a lot less trial and error to find the oven setting that produces it.
>>
>> Rick
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Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv at arrl.net    AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM   NRA LM   SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
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