[time-nuts] Inside of FT1200-100

Ed Palmer ed_palmer at sasktel.net
Mon Sep 26 19:57:54 EDT 2016

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.


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