[R-390] PTO Problems

[Jon Schlegel]

Craig,

I'd say your memory is pretty good because it's 
just as you describe.  The entire arm thing is so 
corroded that I missed the fact that there is 
that smaller secondary arm that pivots on the 
main arm.  I can just make out the spring 
holes.  As you suggested, the spring has long 
turned into some other iron compound and is no 
longer with us.  Guess I'll have to play 
Goldilocks and find a spring that's just right.

Thanks very much, Craig.  That solves that problem.

Jon


At 07:33 PM 11/3/2007 -0700, you wrote:
>Jon,
>
>Going from memory here, I should of taken digital pictures, shame on me.
>Anyway, there should be a small spring pulling those two arms together
>pinching the corrector stack, (where the rollers, wipers, etc., are
>attached). I think mine had one rubber roller, it did have a shaft and
>rolled across the corrector stack. The other arm might have had something
>more like a wiper that slid across the corrector stack.
>
>In any event, search for two small holes on the arms where the spring was
>attached. The spring might of rusted into tiny flakes long ago! A little
>penetrating oil, WD-40 used sparingly where the two arms pivot should free
>things up where the roller and wiper can function.
>
>A trip to the hardware store might be in your future searching for a tiny
>extension spring.
>
>Craig,
>
>-----Original Message-----
>From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
>On Behalf Of Jon Schlegel
>Sent: Saturday, November 03, 2007 6:47 PM
>To: r-390 at mailman.qth.net
>Subject: Re: [R-390] PTO Problems
>
>Hi all,
>
>I've discovered another possible problem with
>this (Motorola) PTO regarding the corrector stack
>follower.  There appear to be two rollers that
>follow the compensator stack (both are now
>frozen).  The one normal looking roller has what
>appears to be a fiber bushing, grayish tan in
>color.  A domed cap appears to retain the bushing
>on its shaft.  I can see vertical striations
>around the circumference of the fiber bushing
>which would tend to indicate that this bushing
>did at one time roll as it followed the corrector stack.
>
>The other roller has neither a domed retaining
>cap nor a fiber bushing.  All that appears to be
>present is a stainless roller.  I found no
>evidence of these seemingly missing parts when I opened the PTO.
>
>When the follower arm is at a position on the
>corrector stack where it's ramping up or down,
>there does not seem to be any radial play of the
>arm on the lead screw.  When the arm is dialed to
>a spot where the corrector stack is flat meaning
>no change in cam height, there is about 10 or 15
>thousandths radial play of the arm.
>
>Is this play normal?  Are there parts missing?  I
>can only imagine that the play I'm seeing could
>cause some nasty hysteresis in the tuning of the receiver.
>
>Regards,
>Jon
>
>
>
>At 01:56 AM 11/3/2007 -0400, you wrote:
> >Renée,
> >
> >Well it's a consensus then.  When I opened it up
> >I finally understood the corrector stack that I
> >hear people talk about.  Guess it's time warm up
> >the counter and generate some more gray hair.
> >
> >Jon,
> >WA3MVM
> >
> >At 10:44 PM 11/2/2007 -0700, you wrote:
> >>Jon-
> >>May I be next thursdays Trash?
> >>actually it is most likely completely repairable.
> >>Renée, K6FSB
> >>
> >>Jon Schlegel wrote:
> >>>Hi all,
> >>>
> >>>The PTO shaft seemed way too stiff so I opened
> >>>it up and found this amazing colony of
> >>>crystalline entities growing all over
> >>>inside.  It's a real mess.  It looks like it
> >>>had a LOT of moisture in it at one time but
> >>>the rest of the receiver doesn't really show
> >>>signs of water problems.  Nevertheless the PTO
> >>>looks original to the receiver (both Motorola).
> >>>
> >>>Should some kind of repair attempt be made or
> >>>should go out with next Thursday's trash?  I
> >>>have an interesting photo but I suppose that
> >>>would be inappropriate for the list.
> >>>
> >>>Regards,
> >>>Jon
> >>>
> >>>
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