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

[Bill Hawkins]

The innards pictures show enough details for some educated guesses.
Most of my PTO work was on R389 PTOs with 50 ring corrector stacks.

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. 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?

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?

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?

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.

Old silica gel packs have to be heated to dry them out before they
may become useful again.

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 9:03 AM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] Cosmos PTO, spring-loaded linearizing core?


One further thought:

My PTO is evidently a Cosmos PTO that had been rebuilt by
Raytheon in the 70's.

I compare the innards of mine (covered with grease, goop, and
shellac) to Jim's pictures at

  http://www.r-390.com/cosmos.htm

and I'm stunned at how shiny his is. In mine the reducing gear was
slopped in tan/grey grease, much of which was running all over the
feed-through wires. Much of this grease was also on the screws/
screwplate etc. too. Some was leaking through into the back of the
can and seeping out of where the inductors screw down to the baseplate.
I've been able to clean up much of it.

I think Raytheon royally screwed my PTO up 30 years ago. But, if
I can get the slug to slide again I'll be home-free!

Tim.
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