From: Garey Barrell 
Subject: Re: [drakelist] R4B PTO repair questions


Jim -

I'm not sure what you are saying yet, but ...

I can't find anything pertinent on WB8RCR's site so can't 
comment on that.

The ball bearings are 1/8" steel and are available from my 
local True Value hardware store. I think it takes either 
nine or ten bearings.  They ARE held in the race by the 
tapered collar on the threaded lead screw, just as you 
suspected.  The Allen head adjustment at the rear of the 
mechanism is only to adjust the pressure on the ball 
bearings at the front of the shaft.

The lead screw does NOT move lengthwise, only the threaded 
follower moves as it threads along the lead screw.

The initial failure in your case was someone turned the knob 
past the stop.  What happens is that the grease hardens with 
time and the plunger fails to come out to stop the rotation. 
  This allows the lead screw to keep turning until the 
follower falls off the end!

What you need to do is to get the ball bearings back in 
there, and then adjust the Allen screw at the rear to just 
take out the side play on the tuning shaft.

The threaded follower that runs on the lead screw then needs 
to be pulled forward while turning the main shaft until the 
threads catch.  You will have to retract the spring plunger 
that is the end stop to allow you to turn it back far enough 
since you are on the "other side" of the mechanical stop.

There is a brass guide rod that extends out the back of the 
PTO through the phenolic block with the diamond shaped hole 
in it.

Once you get it back together mechanically, you need to set 
it for 4.955 MHz at the "rear" and 5.455 MHz at the "front". 
  The plastic dial plate can be slipped by disengaging the 
idler gear by pressing the spring loaded shaft to clear. 
This is also used to get the plate in the right location so 
the stop plunger comes out and engages the "dimple" in the 
gear behind the dial plate.  Takes some fiddling until you 
get everything going in the right direction at the right 
time!  Fine adjustment of the dial plate is made by holding 
the plate and turning the knob, slipping the plate on the shaft.

Let us know how you do.  Or feel free to question anything 
you don't follow.

73, Garey - K4OAH
Atlanta

Jim Pruitt wrote:

> I  recently dug into an R4B to try to find out why it was not working.  One
> thing that I found is the brass plate that sits on the threaded main shaft
> that also push/pulls the coil slug in and out was at the back of the housing
> and was out of threads so the main threaded rod was not picking up that
> slide.  I unscrewed the adjusting allen screw a half turn and that gave me
> part of a thread for the slide to grab but that also pulled that threaded
> shaft back enough that the ball bearings fell out and went everywhere.
> 
> So I am looking for a source for those ball bearings and also need some info
> on how that pto goes back together mechanically.  I have the article from
> WB8RCR's site but do not see what I am looking for (to see how the ball
> bearings are held in there and also whether a washer is needed between the
> brass plate and the housing).  I found a few of the bearings but I must be
> missing something because there was nothing to hold them in the race they
> had fallen out of so they fell again.  I thought the tapered collar on the
> threaded shaft also held the bearings into the race but I either can not get
> that collar far enough forward and being too far forward the shaft will not
> turn.  If it is backed off slightly it will turn but the bearings fall out.
> Also when all the way forward like the there are enough threads for the
> brass plate and it runs off the end and will not start forward again.
> 
> Does anyone have a url or a good description of how the pto goes together
> and still works and travels?
> 
> Thank you.
> 
> Jim Pruitt
> 


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