On 3/1/2016 4:13 AM, Bob Camp wrote:
Is it worth getting it super close? Probably not without a temperature test
setup.
Bob
Right.
It is entirely possible that if you did a temperature test
in an environmental chamber, you would find that you
could get a better tempco by adjusting oven se
Hi
As you do the tweaks, the frequency changes should go from parts in 10^8 to
10^9 to 10^10
per turn. A lot depends on the pot setup and the crystal in terms of how high
it starts. The flip
side to that is your counter and local reference standard need to be able to
measure at least
parts in
Been there and experienced it all to often.
To tweak or not is the question.
"Are you feeling lucky?"
Regards
Paul
WB8TSL
On Mon, Feb 29, 2016 at 1:50 PM, Mark Sims wrote:
> Not to mention that a lot of pots that have been sitting at the same
> setting for years tend to distort the resistance el
Howdy All,
This thread has split into a couple, but I’ll try to respond here to the
various things.
Based on how this crystal warms up, it does appear that it is a BT type
crystal, as it warms up frequency goes up, and as it gets hotter eventually
turns around and heads downhill again.
I’ve m
Not to mention that a lot of pots that have been sitting at the same setting
for years tend to distort the resistance element where the wiper has been
making contact. Then when you make a small adjustment you cannot reach the
value that you need. Ahhh, the subtle wonders of aligning old TM50
Hi
An SC cut OCXO stabilizes a bit faster from the temperature steps. The
procedure Rick described
is indeed the right way to do it for an SC. It takes less time and is
reasonably accurate. For a super
duper job you might come back a day later, but the pot its self (backlash etc)
will probably
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 sta
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
> wrote:
>
>
>
> On 2/28/2016 7:01 AM, Bob Camp wrote:
>> Hi
>>
>> It’s not an electrical issue as much as a heat issue ….
>>
>> Befo
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
Mov
Jim wrote:
Can you tell what the cut is if you have the blank in front of you?
You can do it directly with x-ray crystallography. Otherwise, you
need to characterize multiple crystal parameters and infer the cut
from those, which may not be particularly accurate.
Best regards,
Charles
Hello Nigel ,
I already have done a similar repair on a 10811, described here:
https://www.febo.com/pipermail/time-nuts/2012-January/062228.html
A comparison of the 10811 manual, p. 8-16 and schematic, let me strongly
assume, that the 10544 has exactly the same type of NTC inside.
This NTC a
Hi
Ok a bit more of the story.
It’s easy to simply turn on the device and see how it warms up. Back when it
was made, the
SC did not yet exist. The only thing it could be was a BT. With an X-ray setup
you can absolutely
tell it’s a BT. With the blank and a pair of calipers you can make a dar
Jim,
Why cut it open? It is relatively easy to measure just by power the
oscillator up. Just in this thread is an echo of a discussion we had
many years ago that explains the method.
The temperature curve for AT, BT and SC-cut is known and quite
different, so just measure the heat-up curve f
On 2/28/16 6:23 AM, Bob Camp wrote:
Hi
The whole “BT Cut” issue was a big top secret in HP. They spent a lot of time
obscuring
the fact that they used BT’s. The belief was that if any of the other outfits
figured out that
was what they were doing, the competition would have better OCXO’s.
Hi
Thermistors are often spec’d in terms of a tolerance on a value at a
calibration temperature and a
tolerance on a value for “beta” that goes into the standard thermistor R/T
calculation. Typical parts
are calibrated at something like 25C and you might get 1 or 2% at that point if
you spend e
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 tri
Hi
The whole “BT Cut” issue was a big top secret in HP. They spent a lot of time
obscuring
the fact that they used BT’s. The belief was that if any of the other outfits
figured out that
was what they were doing, the competition would have better OCXO’s.
Watch the frequency as it turns on. An
Hal,
It depends a lot on the thermistor. As with any component, there are higher
precision models that would be pretty repeatable within a model number, and
cheaper ones that will be somewhat less repeatable. In this case I didn’t have
a specific model number, nor specific nominal/beta values,
Mark,
I don’t see that referenced in the documentation, and the frequency adjustment
pot appears to be plastic, but I will compare a non-conductive tool, to a
conductive one to see if it makes a difference.
Nigel
> On Feb 27, 2016, at 19:11, Mark Sims wrote:
>
> Also, when messing with a 105
Also, when messing with a 10544A be aware that that the frequency tuning
adjustment must be made with an insulated tool.
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rich...@karlquist.com said:
> If you replaced the thermistor with an exact replacement, then you shouldn't
> need to change the pot. ...
How repeatable are thermistors? How close do you need/want to get the
temperature?
--
These are my opinions. I hate spam.
Bob,
I’m not sure what type is in it. It *is* a 10544A, not one of the 10811
devices. The references I’ve found indicate the 10544A being an AT type. If
it’s of any use, the date codes on the parts in the oven control circuit
indicate it was built in the latter part of ’77.
I can’t say I’ve go
If you replaced the thermistor with an exact replacement,
then you shouldn't need to change the pot. If you didn't
replace the thermistor with an exact replacement, then you
should carefully measure the resistance of the pot as you
found it. (I hope you did not fool with it already.) From
the p
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
> wrote:
>
> Hello All,
>
> Relatively new to the group, but t
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 c
Thank you very much Didier for your wonderful site and thank you again
Charles for your precious schematic. Finally i'm able to understand
something more!
Ciao!
Luca
iw2lje
Milano
Italy
Il domenica 3 maggio 2015, Didier Juges ha scritto:
> The quarantine is officially over (for this week :)
>
>
The quarantine is officially over (for this week :)
Thanks for the uploads
Didier KO4BB
PS: I am now trying to move the manuals and equipment specific docs out of the
GPS Timing folder into the manufacturer's folders. I realize it may be less
convenient for those who are only interested in tim
Ok, very good, many thanks Gianni, Corby, Charly, for your suggestions and
hints!
I will be here again if there will be interesting topics related with this
item.
Cheers
Luca
iw2lje
Milano - Italy
Il lunedì 27 aprile 2015, Charles Steinmetz ha
scritto:
> That reminds me -- years ago I cleaned up
That reminds me -- years ago I cleaned up, corrected, and annotated a
copy of the HP 10544 schematic. I dug it up and just posted it to
Didier's site (http://www.ko4bb.com/manuals/). When it comes off
quarantine, you can find it by searching for "HP 10544A schematic
corrected and annotated".
Hi all,
Sorry for bad english
The transistor Q4 has the emitter and the collector reversed; R12 is connected
to the collector and the waveform is square wave with duty cycle that depends
on the oven temperature; supply voltage = cold, minimun duty cycle = warm.
It is relatively easy to extract th
Luca,
You can pry out the plastic pins easily.
Then remove the thin foam piece.
Then if I remember correctly you will have to diagram where each color of
wire goes to the edge connector and then unsolder them.
Now you can remove the guts, some pressure on the tuning capacitor thru
the hole will
Hi all,
Have anyone some experience about 10544A repair? I've recently fixed a
10811A, and it is relatively easy to disassemble, but 10544 has not screws
and the manual does not deal about servicing. Can i try to open the box by
removing the white plastic tips without demage something? And then
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