[R-390] Cosmos PTO for 390A - newbie - Help requested

[ANTHONY CASORSO]

The heat shrink is normal. The heater leads have to be unsoldered. Nothing 
special about opening it. Just unwrap the blanket, remove the screws and the 
cover. My insulation was wrapped with a number of turns of black lacing cord 
which I cut at the knot. To reinstall the cord just use one less turn and a 
shoe lace tie so that it can be removed again without cutting.

I had to remove a turn from the endpoint coil to get the endpoint to align. 
Mine turns similarly to what you describe. I expected less resistance too. 
Since this is the only 390a PTO I have touched, I have no point of reference 
for this. My 392 PTO turns easier.

Tony

>From: "Chris Kepus" <ckepus at comcast.net>
>To: <R-390 at mailman.qth.net>
>Subject: [R-390] Cosmos PTO for 390A - newbie - Help requested
>Date: Wed, 21 Nov 2007 21:47:57 -0800
>
>All,
>
>This is a bit long but I would really appreciate your taking a look.  I 
>have
>to operate on a PTO, I believe, and this is the first one I've put a hand
>on.....yep....I haven't taken one apart...yet.
>
>I just picked up a Cosmos PTO that is intended as a spare for my R-390A. I
>have a Collins built R-390A but I am unwilling to pull anything out of it 
>at
>this time.  It is working quite well.  I got the Cosmos because I like the
>fact that Cosmos came up with a PTO design that didn't require tinkering
>with a corrector stack in order to adjust linearity.  Others have pointed
>out that repairing and calibrating the Cosmos (or any PTO) isn't for the
>faint of heart, but it can be done. (I know, fools rush in..) And, as I 
>have
>read in the archives about the repairs that have been done by you all, you
>"git it done"!
>
>Back to my Cosmos.  Although the seller said it was dusty (it is), he 
>didn't
>say the outer cover of the PTO had numerous scratches suggesting a rather
>"rough" storage environment.  Nonetheless, the fragile elements on top of
>the output transformer are in good shape with no observable damage... It is
>also evident that someone had pulled the external cover since only one of
>the screws had the accompanying lock washer.  And the heater and/or
>thermostat was possibly removed.  The screws that retain the inner cover 
>are
>missing.  Is it possible to remove the heater without unsoldering any of 
>the
>leads? The 11-856A Tech Manual talks about unsoldering the thermostat leads
>when replacing it but nothing else except a warning about not removing the
>inner cover. The heater or ther mostat wires did not look as they had been
>unsoldered although under a magnifying glass, it is possible a resoldering
>job was done that was equal to the original  One of my heater leads crosses
>behind the inner cover and has what appears to be shrink wrap over about an
>inch where it is routed across the rear of the inner cover assembly (could
>they have been cut at the top?).  I have posted a number of photos at
>http://www.flickr.com/photos/w7jpg/.  When you click on a photo, it gets
>larger.  Just above the picture on the top left side is a small "All Sizes"
>and magnifying glass icon.  Click on that for yet another enlargement.
>
>How should the PTO shaft feel when rotated by finger power?  I expected low
>resistance and a smooth feeling rotation.  Mine is quite stiff and when
>rotated, has an odd feeling, similar to rotating a shaft with "soft"
>detents...kinda lumpy and not smooth at all.
>
>Is there a manual that shows how to disassemble the PTO (and other modules)
>in detail?  My 11-856A Tech Manual doesn't except.  Can someone tell me
>what's necessary to remove the heater and insulation?  It sounds like the
>thermostat leads may have to be unsoldered but I hate to unsolder something
>if it's not necessary.  Once past that, I can pull the inner cover and take
>photos of the innards. And, Miller's article on "A JOURNEY THROUGH THE
>COSMOS (PTO)" should be very helpful.  Hopefully, I won't find an exploded
>dessicant pack or rusted out assemblies.
>
>I am encouraged by the writing on this list and the articles on R390.com 
>and
>elsewhere by authors like John Harvie, J Miller Dallas Lankford, and Tom
>Marcotte.  There doesn't seem to be many conditions that cannot be 
>repaired.
>
>
>Is there anything I mentioned or that you see in the photos that causes you
>experienced folks to be concerned to the point that I should perhaps have a
>discussion with the seller before proceeding further?  The PTO was 
>described
>as "pulled from a working unit" by the seller (no, it's not Martyn! <g>) in
>response to my question about where it came from.  Otherwise, it's time for
>me to get my feet wet.
>
>Thanks, Happy Thanksgiving and 73,
>Chris
>W7JPG
>
>
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