Author Topic: OCXO tuning screws not working on old equipment  (Read 4541 times)

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Offline rhb

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Re: OCXO tuning screws not working on old equipment
« Reply #25 on: June 29, 2023, 01:38:34 pm »
Yes, yes.  A wooden stake through it's heart, that will liven it up! :-DD

Have you considered becoming a stand up comic?  You're just hilarious!

I made this 30 or 40 years ago with a drill for a lathe and a file.

Reg
 

Offline BillyO

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Re: OCXO tuning screws not working on old equipment
« Reply #26 on: June 29, 2023, 02:29:37 pm »
Have you considered becoming a stand up comic?  You're just hilarious!
Methinks you took my joke completely the wrong way. :palm:

I made this 30 or 40 years ago with a drill for a lathe and a file.
I've done the same using handles from worn out paint brushes and bits of sheet aluminum. :-+
Bill  (Currently a Siglent fanboy)
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Online tautech

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Re: OCXO tuning screws not working on old equipment
« Reply #27 on: June 29, 2023, 08:40:13 pm »
 :-//
Everyone already has a scope probe compensation screwdriver, right ?
Avid Rabid Hobbyist.
Some stuff seen @ Siglent HQ cannot be shared.
 
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Offline BillyO

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Re: OCXO tuning screws not working on old equipment
« Reply #28 on: June 29, 2023, 08:42:53 pm »
:-//
Everyone already has a scope probe compensation screwdriver, right ?
The typical example of such would not be long enough (TWSS) for this application.  A lot of times you need considerably more reach.
« Last Edit: June 30, 2023, 03:18:51 pm by BillyO »
Bill  (Currently a Siglent fanboy)
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Offline J-R

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Re: OCXO tuning screws not working on old equipment
« Reply #29 on: June 29, 2023, 09:45:05 pm »
Well, color me embarrassed, I am remembering now that I had to do the same for my HP5334B.

I happen to have a CRT tookit from back in the day with all the various plastic screwdrivers.  Similar to this: https://www.ebay.com/itm/402973658898
 

Offline 807

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Re: OCXO tuning screws not working on old equipment
« Reply #30 on: June 30, 2023, 12:35:46 pm »
It always surprises me when I see so many videos on youtube where small screwdrivers are used to adjust trimmer pots & capacitors. The screwdriver slips & slides all over the place.

I've been using one of these for decades. It's open one end & enclosed the other end. Stops the blade from sliding off the trimmer.
 

Offline techneut

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Re: OCXO tuning screws not working on old equipment
« Reply #31 on: June 30, 2023, 01:13:52 pm »
I know these, they came with HP probes. I have at least one, somewhere
 

Offline trobbins

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Re: OCXO tuning screws not working on old equipment
« Reply #32 on: July 01, 2023, 01:24:42 pm »
Mine has RS stamped on it.
 

Offline Thomas

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Re: OCXO tuning screws not working on old equipment
« Reply #33 on: July 03, 2023, 10:56:46 am »
On the Racal Dana 1992:
You do realize the two screws visible from the back of the counter are covers, right?
The actual trimmers are visible after removing these.
 
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Offline tverbeureTopic starter

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Re: OCXO tuning screws not working on old equipment
« Reply #34 on: July 07, 2023, 06:31:44 am »
On the Racal Dana 1992:
You do realize the two screws visible from the back of the counter are covers, right?
The actual trimmers are visible after removing these.
I don't think the screws that are marked NE and COAR are covers?

 

Offline Gertjan

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Re: OCXO tuning screws not working on old equipment
« Reply #35 on: July 07, 2023, 07:04:02 am »
Yes, those screws are covers  :)

Under the "Fine" cover screw you will find the trim capacitor you are looking for.

Be very gentl with it! On my Racal-Dana 1998 I only have to touch it for a change in frequency...
And I have to wait 10...15 minutes before the oscillator does not drift anymore.
So, this OCXO does take some time to fine-tune....

regards, Gertjan.
 
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Offline Thomas

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Re: OCXO tuning screws not working on old equipment
« Reply #36 on: July 07, 2023, 10:37:50 am »
Yep, Gertjan is spot on.

Adjusting the screws didn't seem to do anything, and after a day or two I thought "sod it, I'm going in" and removed them.
THERE are the trimmers :o
NOW we're getting somewhere ;D

I really should have taken the hint, because my 1992 has brown fiber washers on the covers :-[
 
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Offline tverbeureTopic starter

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Re: OCXO tuning screws not working on old equipment
« Reply #37 on: July 07, 2023, 09:35:37 pm »
Yep, Gertjan is spot on.

Adjusting the screws didn't seem to do anything, and after a day or two I thought "sod it, I'm going in" and removed them.
THERE are the trimmers :o
NOW we're getting somewhere ;D

I really should have taken the hint, because my 1992 has brown fiber washers on the covers :-[
Amazing! I'm starting to think that this could explain the symptoms of what I'm seeing!  ;D

Just my luck that the two counters that I'm trying to calibrate are using trimmer obfuscation techniques.
 

Offline GigaJoe

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Re: OCXO tuning screws not working on old equipment
« Reply #38 on: July 09, 2023, 03:00:14 am »
im measure Freq quite rare

and very dissatisfied with all internal oscillators.  as it need many hours to stabilize when turn ON, and even 8D direct counter most likely 2 last digits will be incorrect. 
cheap OCXO well insulated with Vref like LT1021-5 , after a reasonable time to age , gives -10 per year stability and no jitter.

high stability OCXO inside an equipment, required constant ON condition, so like meter off but not a reference. in my case usage are few times per year , and it doesn't make sense to keep it running. so i decided to build external 10M ref that constantly on,   well Insulated OCXO consume around 20ma on 12V  vs 120mA open space, and significantly lower jitter,  as a thermal loop control  do it much more precise, due to less heating loss.

as well as I noticed for quartz oscillators need approximately a week  to get stabilized (stop drifting) after extended offline period. so adjustment  better do after long period of ON or STANDBY .
 


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