[R-390] R390A

[JMILLER1706 at cfl.rr.com]

There is also a spring on the Oldham coupler, set between two posts protruding from the two halves that sandwich the coupler.  If this spring is missing, backlash will be very noticeable.  If the coupler is sandwiched too tightly, PTO instability can result as you tune due to excess pressure on the PTO shaft.  My manual says there needs to be 1/32 inch gap between the coupler and the two sandwich halves (whatever you call them), so that the coupler is free to move slightly.  

----- Original Message -----
From: Paul Bigelow <pbigelow at us.ibm.com>
Date: Friday, June 18, 2004 10:19 am
Subject: Re: [R-390] R390A

> 
> 
> 
> 
> 
> Hello,
> 
> The R390a will always take a bit more effort to tune than any 
> receiver with
> an encoder or a simple VFO.  With some rebuild work and 
> lubrication, the
> R390a can be made a bit easier to tune.  The play noted during 
> tuning could
> be the result of improperly set backlash gears or the oldham 
> coupler may be
> worn.  If the olham coupler is worn, it may be possible to reduce 
> play by
> sandwiching some tough, thin, plastic wrap between the coupler and its
> mate, thus filling up the small gaps.  Carefully adjusting the beveled
> gears for the Veeder-Root mechanical readout can reduce the play 
> in that
> mechanism.
> 
> Best regards,
> 
> Paul Bigelow
> EAC 1967 R-390a/URR Ser. No. 121
> Collins 1951 R-392/URR Ser. No. 
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