[time-nuts] Inside of FT1200-100

Chuck Harris cfharris at erols.com
Tue Sep 27 00:24:24 EDT 2016


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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