[time-nuts] Inside of FT1200-100

Christopher Hoover ch at murgatroid.com
Sun Nov 20 00:44:50 EST 2016

tl;dr: I've made some progress and have the1200  oscillator core out of the


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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