[R-390] Re: PTO

[Drew P.]

My version goes something like this:

1. Remove linearizing cam assembly (also known in R-390speak as a 
"corrector stack"), stash in a safe location and replace with an
appropriately-dimensioned straight bar.

2.Using fancy fixture or even just the radio, record PTO frequency
for each 90 degrees (corresponding to 25 Kc points) of rotation.

3.Enter recorded data into computer program which spits out G-code
which is then loaded into CNC machining center.  CNC mills a bar 
having the required correction contour for entire frequency range
of PTO.

4. Replace just-installed straight bar in PTO with contoured bar
and enjoy new found linearity.

I'll do all this in another lifetime, perhaps.

Note that if one uses an aftermarket DRO (EDRO, not the radio's stock 
MDRO) to display frequency, all this linearizing becomes moot.

Drew


Pete Williams wrote:
> G'Day List...having rejuvenated a couple of  Collins 70-H2 pto,is there info
> available as to how best adjust the internal cams for linearity.?
>
> I have read Ray Osterwalds comments ex past issue of ER but this only
> addresses the 100kHz -one  turn of the shaft-calibration points.
>
> It would seem to be  laborious process to adjust these cams as there are in
> excess of 60 for the  complete travel of the  core, although, they are not
> all required for  adjustment for the 1 mHz  range .
>
> How the factory did it is one thing-- how one might do it now is  another
>
> My preliminary excursion into this finesse  appears to show that adjusting
> at the 100kHz points seems to take reasonable  care of what's in between,
> bit I'm sure there was a bit more to it, albeit labor intensive .
> A bit more light on this would be  appreciated.
> Tks 
> Pete VK3IZ