Re: [time-nuts] HP 10544A Repair

[Richard (Rick) Karlquist]

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 set point
to have a slight offset from the turnover.  In this regime,
the crystal drift would cancel out the tempco of the
electronics.  This all depends on the crystal tempco,
the electronics tempco, and the respective thermal gains
to the crystal and the electronics.  But there will be
an adjustment giving zero tempco (at least around a single
ambient temperature).  My old boss at Agilent used to
call this sort of thing a "hero experiment", which he
used as a pejorative term.

Rick
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 10^10 to get it set.

Is it worth getting it super close? Probably not without a temperature test 
setup.

Bob

> On Feb 29, 2016, at 11:14 PM, Nigel Vander Houwen 
>  wrote:
> 
> 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 managed to tune the oven to where the peak seems to be. It’s a many turn 
> potentiometer (something like 21 turns), that plays a small portion on the 
> resistance, so +/- about a quarter turn at the peak didn’t seem to really 
> impact the frequency. I left it in the middle of that range.
> 
> My replacement thermistor has a lower beta than what it seems the original 
> had. The original thermistor being specified at 9.93K @ 80C, and the 
> calculator shows mine at about 12K @ 80C. Since the circuit for this crystal 
> has a 10K + 9K & the 2K POT on one side of an op-amp comparator, and a 10K + 
> the thermistor on the other side, I added a 2.2K resistor to the POT leg of 
> that voltage divider to bring the tuning range about to where it was stock, 
> as I found that unaltered, with the new thermistor I couldn’t set the oven 
> temperature low enough, every frequency was on the downhill slope past the 
> peak.
> 
> I appreciate Frank’s offer for a close to original thermistor, however I’m 
> not in the netherlands (despite my name), and I’ve already got a reasonably 
> close replacement epoxied into the oven like the original was.
> 
> Now I’ll leave it run for a while and see about tuning the frequency. I’ve 
> got it pretty close at the moment, but the coming days/weeks will show their 
> own colors.
> 
> I would like to thank everyone for the insight around getting this thing 
> tuned up. It’s sincerely appreciated.
> 
> I’ll probably start designing a DAC + Phase comparator board to GPS 
> discipline this old crystal. Have to see how that ends up comparing to my 
> thunderbolt.
> 
> Nigel
> 
>> On Feb 28, 2016, at 15:03, Bob Camp  wrote:
>> 
>> 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 darn 
>> good guess it’s a BT. 
>> 
>> Since HP did not make their own blanks, the “competition” was the source of 
>> their blanks. No need
>> for those guys to guess about anything. 
>> 
>> Despite all of this logical and rational thinking, the BT remained a “top 
>> secret” sort of thing as far
>> as (at least certain people at) HP were concerned. Those who were concerned 
>> also had the route
>> to the HP PR machine so that’s the story that went out to the world. 
>> 
>> Those involved left HP long ago. The whole thing became a non-issue once the 
>> 10811 came out. 
>> What is the most amazing thing to me is that 30 years after it became a 
>> non-issue there still is 
>> confusion about the topic. 
>> 
>> Bob
>> 
>>> On Feb 28, 2016, at 11:48 AM, jimlux  wrote:
>>> 
>>> 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.
 
>>> 
>>> 
>>> Can you tell what the cut is if you have the blank in front of you?
>>> 
>>> Wouldn't the competition just buy an instrument with the oscillator, saw it 
>>> open, and measure it?
>>> 
>>> 
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Re: [time-nuts] HP 10544A Repair

[paul swed]

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 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
> TM500 series modules...
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Re: [time-nuts] HP 10544A Repair

[Nigel Vander Houwen]

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 managed to tune the oven to where the peak seems to be. It’s a many turn 
potentiometer (something like 21 turns), that plays a small portion on the 
resistance, so +/- about a quarter turn at the peak didn’t seem to really 
impact the frequency. I left it in the middle of that range.

My replacement thermistor has a lower beta than what it seems the original had. 
The original thermistor being specified at 9.93K @ 80C, and the calculator 
shows mine at about 12K @ 80C. Since the circuit for this crystal has a 10K + 
9K & the 2K POT on one side of an op-amp comparator, and a 10K + the thermistor 
on the other side, I added a 2.2K resistor to the POT leg of that voltage 
divider to bring the tuning range about to where it was stock, as I found that 
unaltered, with the new thermistor I couldn’t set the oven temperature low 
enough, every frequency was on the downhill slope past the peak.

I appreciate Frank’s offer for a close to original thermistor, however I’m not 
in the netherlands (despite my name), and I’ve already got a reasonably close 
replacement epoxied into the oven like the original was.

Now I’ll leave it run for a while and see about tuning the frequency. I’ve got 
it pretty close at the moment, but the coming days/weeks will show their own 
colors.

I would like to thank everyone for the insight around getting this thing tuned 
up. It’s sincerely appreciated.

I’ll probably start designing a DAC + Phase comparator board to GPS discipline 
this old crystal. Have to see how that ends up comparing to my thunderbolt.

Nigel

> On Feb 28, 2016, at 15:03, Bob Camp  wrote:
> 
> 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 darn 
> good guess it’s a BT. 
> 
> Since HP did not make their own blanks, the “competition” was the source of 
> their blanks. No need
> for those guys to guess about anything. 
> 
> Despite all of this logical and rational thinking, the BT remained a “top 
> secret” sort of thing as far
> as (at least certain people at) HP were concerned. Those who were concerned 
> also had the route
> to the HP PR machine so that’s the story that went out to the world. 
> 
> Those involved left HP long ago. The whole thing became a non-issue once the 
> 10811 came out. 
> What is the most amazing thing to me is that 30 years after it became a 
> non-issue there still is 
> confusion about the topic. 
> 
> Bob
> 
>> On Feb 28, 2016, at 11:48 AM, jimlux  wrote:
>> 
>> 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.
>>> 
>> 
>> 
>> Can you tell what the cut is if you have the blank in front of you?
>> 
>> Wouldn't the competition just buy an instrument with the oscillator, saw it 
>> open, and measure it?
>> 
>> 
>> ___
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> 
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[time-nuts] HP 10544A Repair

[Mark Sims]

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 TM500 series 
modules...   
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 limit you. 
With another parameter to read out (pot voltage maybe) as you do the set, 
things could get more
precise. 

AT’s and BT’s are not quite as forgiving as an SC. The process I outlined is a 
bit of an exaggeration, but
it gives you a good idea of what you are in for. Doubly so if this is your 
first attempt to do a blind hole
adjust on a pot to 1/32 turn ….(engage without moving it, back off for the 
backlash, return, past 
previous point, stop at 1/32 .. so much fun).

Bob


> On Feb 28, 2016, at 11:19 PM, Glenn Little WB4UIV 
>  wrote:
> 
> 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 
>>>  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
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
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>> 
> 
> -- 
> ---
> Glenn LittleARRL Technical Specialist   QCWA  LM 28417
> Amateur Callsign:  WB4UIVwb4...@arrl.netAMSAT 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
> of the Amateur that holds the license"
> ---
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Re: [time-nuts] HP 10544A Repair

[Glenn Little WB4UIV]

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  
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 LittleARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIVwb4...@arrl.netAMSAT 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
of the Amateur that holds the license"
---
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 ….
>> 
>> 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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Re: [time-nuts] HP 10544A Repair

[Richard (Rick) Karlquist]

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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Re: [time-nuts] HP 10544A Repair

[Charles Steinmetz]

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


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[time-nuts] HP 10544A Repair

[Frank Stellmach]

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 also has 100k @ 25°C, and 9k93k @ 80.0°C, 8k60 @ 84.0°C as the 
max. temperature.


I chose the new NTC from epcos for an exact match of the  R/T curve, and 
it's a precision type, 1% for R25 and B values , very reproducible, 
interchangeable and stable. The sample had been characterised by epcos 
at 25°C and 100°C, so R25 and B are extremely well in the middle of the 
spec, and I have 9 EA left...


Maybe you need one.. if you are located in NL, that would be no problem.

I did not find the 10544 manual, describing the correct procedure to 
correctly trim R4, but I assume you would 'simply' have to find a 
minimum or maximum in frequency, depending on the characteristics of the 
BT cut.


But I also assume that this trimmer is not accessible from outside?
Maybe difficult to trim , in this case.

Frank
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 darn good 
guess it’s a BT. 

Since HP did not make their own blanks, the “competition” was the source of 
their blanks. No need
for those guys to guess about anything. 

Despite all of this logical and rational thinking, the BT remained a “top 
secret” sort of thing as far
as (at least certain people at) HP were concerned. Those who were concerned 
also had the route
to the HP PR machine so that’s the story that went out to the world. 

Those involved left HP long ago. The whole thing became a non-issue once the 
10811 came out. 
What is the most amazing thing to me is that 30 years after it became a 
non-issue there still is 
confusion about the topic. 

Bob

> On Feb 28, 2016, at 11:48 AM, jimlux  wrote:
> 
> 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.
>> 
> 
> 
> Can you tell what the cut is if you have the blank in front of you?
> 
> Wouldn't the competition just buy an instrument with the oscillator, saw it 
> open, and measure it?
> 
> 
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Re: [time-nuts] HP 10544A Repair

[Magnus Danielson]

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 from room temperature to 
oven temperature will be distinct for these types. I think the IT-cut 
can also be identified uniquely this way.


If you have the crystal blank, you can use X-ray to see the 
crystal-orientation.


Cheers,
Magnus

On 02/28/2016 05:48 PM, jimlux wrote:

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.




Can you tell what the cut is if you have the blank in front of you?

Wouldn't the competition just buy an instrument with the oscillator, saw
it open, and measure it?


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Re: [time-nuts] HP 10544A Repair

[jimlux]

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.




Can you tell what the cut is if you have the blank in front of you?

Wouldn't the competition just buy an instrument with the oscillator, saw 
it open, and measure it?



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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 enough 
money. With a normal tolerance on beta, that 1 or 2% becomes a small part of 
the tolerance by the time 
you get past 40C. 

Can you get a large batch calibrated at a higher temperature? Sure you can. 
They already are expensive
parts and when you put an adder on top of that … the finance guys math goes 
tilt. If you need a very 
accurate number, the old style approaches were to turn hunt the oven or to 
measure the value of the part
in a “local standard temperature of 95C” oil bath.

Pretty much nobody does an OCXO either of those ways anymore. It’s all 
automated and uses a couple
of measurements to set the part to best measured temperature performance. At 
some point in the performance 
equation, you don’t do anything more than take a guess at oven temperature and 
things work “good enough”
for that spec. 

Bob  



> On Feb 27, 2016, at 11:21 PM, Hal Murray  wrote:
> 
> 
> 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.
> 
> 
> 
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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


> On Feb 28, 2016, at 2:53 AM, Nigel Vander Houwen 
>  wrote:
> 
> 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 10544A be aware that  that the frequency tuning 
>> adjustment must be made with an insulated tool.  
>> 
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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 AT will go down a bunch in frequency as 
it warms up. 
An SC or BT will go up. 

Bob

> On Feb 27, 2016, at 11:38 PM, Nigel Vander Houwen 
>  wrote:
> 
> 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 got a whole lot of experience looking at this, but should I 
> expect to see a curve along the values, of which there would either be a 
> minimum or maximum? That would be fairly indicative.
> 
> Rick,
> 
> The thermistor was not an exact replacement, and I couldn’t find any 
> specifications beyond 9.93KOhm @ 80C referenced on the schematic. I don’t 
> know that the pot wasn’t turned during the original debugging of why the 
> crystal wasn’t on frequency, so my best bet now unfortunately is to find the 
> set point myself.
> 
> Nigel
> 
> 
> 
>> On Feb 27, 2016, at 19:39, Richard (Rick) Karlquist  
>> wrote:
>> 
>> 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 pot resistance, and the thermistor curve specs of
>> the original thermistor, you should be able to calculate
>> the factory oven temperature set point.  You can then
>> calculate the new pot resistance based on the specs
>> for the replacement thermistor.
>> 
>> Trying to determine the turn over temperature as you
>> described (which was done with an automated system
>> in the E1938A) would be extremely cumbersome when
>> done by hand.  It would be a last resort if you fooled
>> with the pot.
>> 
>> Rick
>> 
>> On 2/27/2016 6:48 PM, Nigel Vander Houwen 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
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
>>> 
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Re: [time-nuts] HP 10544A Repair

[Nigel Vander Houwen]

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, so I chose a 
reasonable 100K NTC thermistor, and am adjusting for that.

Nigel

> On Feb 27, 2016, at 20:21, Hal Murray  wrote:
> 
> 
> 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.
> 
> 
> 
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Re: [time-nuts] HP 10544A Repair

[Nigel Vander Houwen]

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 10544A be aware that  that the frequency tuning 
> adjustment must be made with an insulated tool.   
> 
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[time-nuts] HP 10544A Repair

[Mark Sims]

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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Re: [time-nuts] HP 10544A Repair

[Hal Murray]

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.



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Re: [time-nuts] HP 10544A Repair

[Nigel Vander Houwen]

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 got a whole lot of experience looking at this, but should I 
expect to see a curve along the values, of which there would either be a 
minimum or maximum? That would be fairly indicative.

Rick,

The thermistor was not an exact replacement, and I couldn’t find any 
specifications beyond 9.93KOhm @ 80C referenced on the schematic. I don’t know 
that the pot wasn’t turned during the original debugging of why the crystal 
wasn’t on frequency, so my best bet now unfortunately is to find the set point 
myself.

Nigel



> On Feb 27, 2016, at 19:39, Richard (Rick) Karlquist  
> wrote:
> 
> 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 pot resistance, and the thermistor curve specs of
> the original thermistor, you should be able to calculate
> the factory oven temperature set point.  You can then
> calculate the new pot resistance based on the specs
> for the replacement thermistor.
> 
> Trying to determine the turn over temperature as you
> described (which was done with an automated system
> in the E1938A) would be extremely cumbersome when
> done by hand.  It would be a last resort if you fooled
> with the pot.
> 
> Rick
> 
> On 2/27/2016 6:48 PM, Nigel Vander Houwen 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
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
>> 
> ___
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Re: [time-nuts] HP 10544A Repair

[Richard (Rick) Karlquist]

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 pot resistance, and the thermistor curve specs of
the original thermistor, you should be able to calculate
the factory oven temperature set point.  You can then
calculate the new pot resistance based on the specs
for the replacement thermistor.

Trying to determine the turn over temperature as you
described (which was done with an automated system
in the E1938A) would be extremely cumbersome when
done by hand.  It would be a last resort if you fooled
with the pot.

Rick

On 2/27/2016 6:48 PM, Nigel Vander Houwen 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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Re: [time-nuts] HP 10544A Repair

[Bob Camp]

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 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
> ___
> time-nuts mailing list -- time-nuts@febo.com
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[time-nuts] HP 10544A Repair

[Nigel Vander Houwen]

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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Re: [time-nuts] HP 10544A repair

[Luca Dal Passo]

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 :)
>
> 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 timing information,
> but it makes the overall organization of the site easier for me and (I
> hope) for a majority of users.
> Until that is complete, you can find HP timing info in two folders, the
> GPS Timing folder and in the HP Agilent folder for instance. The search
> works through the entire site, so finding stuff should not be harder.
> As I am sure most of you have noticed, I have implemented a Content
> Management System. The main reason was to make the site easier to manage. A
> side benefit is to keep my Google rankings up since the CMS is mobile
> friendly and now Google ranks down the sites that are not. I am sorry for
> those who lament the loss of Comic Sans... The old site is still there, the
> old links still work but the old pages won't be maintained. After a while,
> they will go away.
>
>
> On April 27, 2015 4:14:07 AM CDT, Charles Steinmetz  > wrote:
> >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".
> >
> >Best regards,
> >
> >Charles
> >
> >___
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>
> --
> Sent from my Motorola Droid Razr HD 4G LTE wireless tracker while I do
> other things.
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Re: [time-nuts] HP 10544A repair

[Didier Juges]

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 timing information, but it 
makes the overall organization of the site easier for me and (I hope) for a 
majority of users.
Until that is complete, you can find HP timing info in two folders, the GPS 
Timing folder and in the HP Agilent folder for instance. The search works 
through the entire site, so finding stuff should not be harder.
As I am sure most of you have noticed, I have implemented a Content Management 
System. The main reason was to make the site easier to manage. A side benefit 
is to keep my Google rankings up since the CMS is mobile friendly and now 
Google ranks down the sites that are not. I am sorry for those who lament the 
loss of Comic Sans... The old site is still there, the old links still work but 
the old pages won't be maintained. After a while, they will go away.


On April 27, 2015 4:14:07 AM CDT, Charles Steinmetz  
wrote:
>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".
>
>Best regards,
>
>Charles
>
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-- 
Sent from my Motorola Droid Razr HD 4G LTE wireless tracker while I do other 
things.
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Re: [time-nuts] HP 10544A repair

[Luca Dal Passo]

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, 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".
>
> Best regards,
>
> Charles
>
> ___
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Re: [time-nuts] HP 10544A repair

[Charles Steinmetz]

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".


Best regards,

Charles

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Re: [time-nuts] Hp 10544A repair

[gianni]

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 the boards and access the oven controller and 
amplifier AGC.
Pay attention to the black wires (NTC) and red (oven heather).
Remember that the output impedance is about 1000 ohm as for data sheet and 
check the power supply.
Semiconductor type
Q4 = MJE700
Q2 = MPS A12
Q3 = 2N2646
U1 = LM201NPN = 2N3906

if you want more detailed information in Italian you can contact me directly.
Best regards
John (Gianni)
Il 26 aprile 2015, Luca Dal Passo  ha scritto:
> 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 how to
> correctly extract the inner stuff? The malfunction is that the oven monitor
> signal is bad and the 10MHz signal has low amplitude and very bad shape
> (distorted), but the output frequency is ok and oven heather and
> control seems to be ok too (current drain from power supply is ok). So
> there are probably some defective components in the output buffer zone of
> the circuit. Another question is that the schematic (thanks to KO4BB!)
> seems to have a mistake about drawing of the oven monitor signal (the pin
> 11 wire is taken between the thermal fuse and the power darlington: how
> does can it work in that way?).
> Thanks and regards
> Luca
> iw2lje
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[time-nuts] Hp 10544A repair

[cdelect]

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 aid in getting it to slide out.

The distortion on the output might be normal. If you just hook  scope to
it they almost allways look distorted.

You have to properly load the output into 1KOhm to get the sine wave.

Cheers,

Corby

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[time-nuts] Hp 10544A repair

[Luca Dal Passo]

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 how to
correctly extract the inner stuff? The malfunction is that the oven monitor
signal is bad and the 10MHz signal has low amplitude and very bad shape
(distorted), but the output frequency is ok and oven heather and
control seems to be ok too (current drain from power supply is ok). So
there are probably some defective components in the output buffer zone of
the circuit. Another question is that the schematic (thanks to KO4BB!)
seems to have a mistake about drawing of the oven monitor signal (the pin
11 wire is taken between the thermal fuse and the power darlington: how
does can it work in that way?).
Thanks and regards
Luca
iw2lje
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