[R-390] New Project (PTO)

[JMILLER1706 at cfl.rr.com]

Sounds like a loose clamp on the PTO linkage.  Check the clamps holding 
the coupler on the PTO shaft and also on the main drive shaft coming 
from the front panel.  If they are loose the PTO shaft will slip.  
These clamps have been known to crack, or the screw threads have 
stripped,  after prolonged maintenance activity.  Check for that also - 
someone may have broken a clamp in the past.  You will need a "Bristol" 
type driver to tighten the clamps.   If the clamp is bad, you will need 
a new one (you can probably get a spare from someone on the list). The 
spacings within the oldham coupler and its two mating discs should be 
around 1/32. You can eyeball it.   But not too close or too tight 
because then you can get PTO instability if it binds.  To correct the 
spacing you loosen one of the clamps and use a thin screw driver to 
gently push the coupler surfaces together (or spread them apart as 
needed).  There should also be a little tensioner spring between the 
two little posts on 
the two coupler discs - this is to prevent tuning backlash.  It will 
tune without the spring but you will notice a slight amount of 
backlash.  To initially get the PTO back synchronized with the coil 
linkages again, tune the radio dial readout to the frequency a known 
station on the dial.  WWV at 10 Mhz is good, or a local broadcast 
station.  Loosen the coupler coming from the panel side, and then spin 
the PTO shaft by hand (using its coupler disc as a "knob") until you 
hear a peak in noise or you hear the station (but do not allow the dial 
readout to change)  Then retighten the clamps.  You should be OK from 
that point on.

----- Original Message -----
From: Carole White-Connor <carolew at bellatlantic.net>
Date: Thursday, February 22, 2007 8:05 am
Subject: [R-390] New Project (PTO)
Cc: r-390 at mailman.qth.net

> Thank you, everyone, for your help. As always, your knowledge 
> staggers me. More
> than that, your willingness to help out shows just what a great 
> group you are.
> 
> The problem is in the PTO linkage. The KC knob does not turn the 
> PTO shaft.
> 
> In looking at the Oldham coupler, I have a stainless steel disc 
> between the KC
> knob drive and the PTO shaft. It has a groove that mates with a 
> ridge on the KC
> knob drive. There appears to be groove in the back that do not 
> mate with the
> PTO shaft. The stainless steel disc fits very loosely between the 
> KC knob drive
> and the PTO shaft. It's definitely more than the 1/32" gap shown 
> in the Y2K
> manual. There is no anti-backlash spring.
> 
> 1. My first question is whether there should be one or two discs 
> between those
> drives. I'm looking at Pete Wokoun's diagram in the Y2K manual 
> (Figure 6-4) and
> it's a little hard to tell.
> 
> 2. If there is only supposed to be one disc, why is everything so 
> loose and why
> doesn't the KC knob turn the PTO shaft? What's the fix?
> 
> 3. I've never had to work on a PTO or Oldham coupler before so I 
> need simple
> instructions (very simple, might be more like it!).
> 
> 4. When I turn the PTO shaft a little by hand, I receive stations 
> loud and
> clear, so I'm pretty sure the linkage is the problem.
> 
> As always, thanks.
> 
> Joe Connor
> 
> 
> 
> 
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