[time-nuts] Inside of FT1200-100
Bob Camp
kb8tq at n1k.org
Wed Nov 23 14:36:18 UTC 2016
Hi
…. but … you might *build* one of those oscillators.
The Dewar flask OCXO thing died out many decades ago. The main
reason was size. A secondary reason was the fragile nature of a Dewar
(they don’t take well to being dropped … I have empirical evidence).
Neither one of these issues is particularly significant for a Time Nut basement
project. Since they tend to be a bit on the big side, super dense PCB’s are
not a major advantage building them. The same auction sites that will sell
you questionable OCXO’s will sell you nice working Dewars as components
for your build.
Bob
> On Nov 23, 2016, at 8:33 AM, paul swed <paulswedb at gmail.com> wrote:
>
> Chris enjoying the pictures. Most likely I will never run into one of these
> oscillators. But it is nice to know that you have gone "where no man has
> gone before". Star Trek? Not sure.
> Regards
> Paul
> WB8TSL
>
> On Wed, Nov 23, 2016 at 1:45 AM, Christopher Hoover <ch at murgatroid.com>
> wrote:
>
>> A Wiha nutdriver set later and I'm in:
>>
>> https://goo.gl/photos/SDHtvgFmftQq6vYJA
>>
>> See the last two pictures.
>>
>> I will disassemble the board stack and work out some schematics next.
>>
>> Thanks everyone.
>> -ch
>> 73 de AI6KG
>>
>> On Nov 20, 2016 5:19 AM, "J. L. Trantham" <jltran at att.net> wrote:
>>
>> Christopher,
>>
>> Enjoyed the pictures.
>>
>> You might want to look at these items on theBay.
>>
>> 381408412092
>>
>> 311736541103
>>
>> I've had the same issue and broke down and bought a set of these small nut
>> drivers.
>>
>> Good luck.
>>
>> Joe
>>
>> -----Original Message-----
>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of
>> Christopher Hoover
>> Sent: Saturday, November 19, 2016 11:45 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Inside of FT1200-100
>>
>> tl;dr: I've made some progress and have the1200 oscillator core out of the
>> dewar:
>>
>> https://goo.gl/photos/SDHtvgFmftQq6vYJA
>>
>>
>>
>> I got some 5 thou brass stock and worked it between the rubber sheet and
>> the dewar.
>>
>> That seemed to help but it was insufficient free things up -- I busted off
>> the unused solder lug trying to pull the core out with it.
>>
>> Having not a lot to lose, I took a chance that the screws going into the
>> TO-23 went into threaded holes (rather than being clearance holes with nuts
>> inside). This was indeed the case.
>>
>> With two 6-32 threaded rods into the TO-23 threaded holes and and an
>> appropriately machined piece of mild steel bar stock suspended across the
>> case <https://goo.gl/photos/1pfiN2GX3WxYCSbg8>, I was able to easily get
>> the oscillator core out of the dewar by evenly tightening the the nuts on
>> the bar. Really easily -- I might have been able to pull it out by just
>> pulling on the bar stock. I don't know if the shim stock shenanigans were
>> even needed.
>>
>> Despite running out the three sloted screws on the "top" around the
>> circumference, I'm not into the inside yet. I don't have the right
>> thin-walled socket to remove the nuts at the opposite end.
>>
>> I found an epoxy covered hole on the top. It is/was under the green blob
>> midway between 1 and 2 o'clock in this picture here <
>> https://goo.gl/photos/
>> iHbSbqwBiKD7NRfJ6>.. There was something blue and
>> at this point crumbly underneath it. Not sure yet what, if anything, is
>> beyond all of that. I'm hoping for a trimmer cap. :-)
>>
>> -- Christopher.
>> 73 de AI6KG
>>
>>
>>
>>
>> On Mon, Sep 26, 2016 at 9:24 PM, Chuck Harris <cfharris at erols.com> wrote:
>>
>>> Back when I was going to work on mine, I was thinking of prying the
>>> rubber away from the aluminum oven with something like a feeler gauge,
>>> but also using some naptha (lighter fluid) to help release any
>>> adhesive... I didn't get around to doing it, but that was the way I
>>> was going to progress.
>>>
>>> -Chuck Harris
>>>
>>> Ed Palmer wrote:
>>>>
>>>>
>>>> On 2016-09-26 10:00 AM, Christopher Hoover <ch at murgatroid.com> wrote:
>>>>>>>
>>>>>>> You might be able to slide something like a feeler guage down
>>>>>>> between
>>> the
>>>>>>> oven and the rubber blanket to break the oscillator free. The
>>>>>>> oven
>>> on mine
>>>>>>> is a plain metal cylinder. This way, the rubber sheet should
>>>>>>> protect
>>> the
>>>>>>> Dewar from your feeler guage. On mine, the mounting bolts for
>>>>>>> the
>>> 2N3792
>>>>>>> transistor both have ground lugs. I think I see them on yours.
>>>>>>> You
>>> could
>>>>>>> hook something through the ground lugs and use that to pull the
>>> oscillator
>>>>>>> out of the rubber sheet and then remove the sheet later.
>>>>>>>
>>>>> Thanks Ed,
>>>>>
>>>>> I think the rubber sheet on mine is against metal. I haven't yet
>>>>> seen
>>> the
>>>>> glass dewar.
>>>>>
>>>>> The adhesion is huge.
>>>>>
>>>>> Do you know if the holes opposite the 2N3792 are threaded? If they
>>> are, I
>>>>> might try running the screws out and using those holes with longer
>>> screws
>>>>> as my pull points. I can't pull on the lugs hard enough -- I've
>>> tried.
>>>>>
>>>>> -christopher.
>>>>> 73 de AI6KG
>>>>
>>>> Yes, you have seen the Dewar. The silvery ring that's outside the
>>> rubber is the top
>>>> of the Dewar. What you have to do is unstick and unfold the rubber
>>> starting from the
>>>> open area in the center. Work your way outward. The rubber is only
>>>> 2
>>> or 3 mm
>>>> thick. Once you completely clear the rubber out of the way, you'll
>>>> see
>>> the edge of
>>>> the oven. The TO-3 transistor is mounted on top of the oven assembly.
>>> Once you can
>>>> see the edge, you have to slide something like a long feeler gauge
>>>> down
>>> along the
>>>> edge of the oven to break it free from the rubber. Work your way
>>>> all
>>> around the
>>>> oven. It's about 85 mm long. It'll still be stuck on the bottom,
>>>> but
>>> you might be
>>>> able to pull it free.
>>>>
>>>> When I took mine apart, I ended up tearing off all the rubber at the
>>>> top
>>> and then
>>>> cutting out that ring of hard foam to get at the Dewar so I could
>>>> smash
>>> it more. I'm
>>>> guessing you'd rather not do that! :) But sacrificing the rubber on
>>>> the
>>> top might be
>>>> okay, if you have to.
>>>>
>>>> Sorry, but I don't know if the mounting holes for the transistor are
>>> threaded or
>>>> not. In any case, since the oven and Dewar are bonded to the
>>>> rubber,
>>> you're pulling
>>>> on the Dewar when you pull on the oven. Not a good plan until you
>>>> break
>>> the oven
>>>> free from the rubber. Those Dewars are built in a rather fragile
>>> manner. Your
>>>> typical home Thermos is much more robust.
>>>>
>>>> Ed
>>>>
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