[R-390] Cosmos PTO, spring-loaded linearizing core?

[Bill Hawkins]

OK, the ring is not the main spring. I do see the red part with
the white dot in Jim's pictures. What I can't see is how to
remove the coil assembly, with that long steel base that surely
could contain a spring. The picture with "The two halves of the
PTO being separated ..." shows what appears to be a wrench flat
at the end of the "steel" (or some gray metal) base that is close
to the frame. Have you disassembled it that far?

If you do have the coil assembly free of the PTO, can you see a
way to look in the steel barrel? The spring has to push the rod
all the way out, so the fixed end of the spring is near the coil.
The other end pushes on the rod, probably using a circlip snapped
onto the rod.

OTOH, Cosmos didn't machine anything that didn't have to be machined.
Perhaps the red rod is hollow. The inside end pushes against the
spring. The outside end pushes against something like a rivet head
on the end of the inner rod that attaches to the coil slug. If that's
the way it's built, I wouldn't expect the spring to be gunked up.
More likely the rivet head broke off - but you can see something
extending from the outer rod. You ought to be able to push the rod
a little further into the coil, or go around and push on the core to
get the rod to move out. The core is probably fragile.

Bill Hawkins


-----Original Message-----
From: r-390-bounces at mailman.qth.net
[mailto:r-390-bounces at mailman.qth.net]On Behalf Of Tim Shoppa
Sent: Monday, February 27, 2006 11:30 AM
To: r-390 at mailman.qth.net
Subject: RE: [R-390] Cosmos PTO, spring-loaded linearizing core?


Bill wrote:

> The innards pictures show enough details for some educated guesses.

Yeah, your guesses are pretty good based on the pictures, but... :-).

> The solid ring that holds the slider that contacts the ends of the
> adjusting screws must be attached to the frame at some point, probably
> opposite the linearizing coil. It can't turn.

You are correct, it is held on by two screws.

> That means it could be
> the spring that you are looking for. If it isn't springy, that could
> be the problem. Does the PTO look like it had been overheated?

It is springy. But there's no way it can "pull" the slug out of the
coil.
Look at Jim's pictures of the ring and its riders: vacing the outside
is the metal triangle that rides the screw, and on the inside you
can see a red-with-white-cap thing that must ride the back.

The PTO does not look overheated but it is way greased up compared
to Jim's pictures. (He doens't say if it looked that way when he opened
it or if he cleaned it up to make it shiny).

> You can't put a spring in the end of the coil opposite the slider,
> or it would be detuned. Seems like you have to attach the screw
> from the slug to the ring with the slider, to get spring action.
> That means the relaxed spring must be well away from the frame
> (at the coil) when the frame is separated from the ring with the
> screws. You'd have to disassemble the PTO as shown in Jim's
> pictures. Once you've done that, you ought to be able to press
> gently on the slider, in the direction of the coil, closing the
> gap between the slider and the frame holding the coil. Can you
> do that? Do you feel spring action, so that the gap widens when
> you remove pressure on the slider?

My PTO is completely torn down. I've removed the
linearizing coil (you see it in Jim's pictures - there a phenolic form
on a long metal base, and there are two cheese-head screws that
hold the base to the plate which you cannot see.)

There is no spring aciton and no slide action either.

> If the slider ring is acting like a spring, then the rod from the
> coil slug must be attached to the ring. Can you see if that's true?
> The detailed pictures don't show that detail. If it isn't attached,
> can you see how it might have been before it broke away?

It is not attached, and it does not slide. I don't think it was ever
attached. There is a black plastic nub that must've ridden the back
of the ring. The ring can push on the nub, but it cannot pull, so there
must be a spring and slider to push the nub back out.

My best theory (while I do not have the PTO in front of me!)
is that the sliding component must be seized inside the base
of the inductor. (You can see the base in Jim's pictures, it's
the long metal thing on which the phenolic coil form sits. You
also see the nub sticking out and contacting the ring.)

The base is long enough that it must have the slide-spring
mechanism in its base.

My nub looks different than the one in Jim's picture (which now that
I look at it again is RED with a WHITE tip). Mine is black. I don't
think
it's a "mismatched" part because it fits very snugly in the bottom of
the
metal inductor base. Although it is vaguely possible that the idiots
at Raytheon modified mine, I'm surely HOPING they did not.

> The adjuster screws don't hold nitrogen pressure. The case is
> sealed with the big O-ring, the 2 feedthrus and the two screw caps
> for linearity and endpoint adjustment.

OK, so the first time you do the endpoint adjustment the nitrogen
poofs out. That's what it seemd like to me :-).

Tim.
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