[R-390] Cosmos PTO question

Wed, 04 Sep 2002 16:12:37 -0700

Phil,  I did the "remove a turn" thing on my Cosmos pto per the description by
Tom.  Getting into the unit was pretty straightforward after looking at the nice
pics that were posted by Jim Miller N4BE of the innards.  I removed 1 turn and
brought a 10 khz error down to within 1 or 2 khz,  which was good enough for me.  I
haven't had any problems with the pto,  though I haven't really checked it
carefully since,  Dan.

"Tom M." wrote:

> Phil:
>
> Yes, the Cosmos has two caps, one for linearity and one for endpoint.  When
> looking at the front of the PTO, the cap to the left gives access to linearity.
>
> Behind the transformer you'll find the cap on the right.  Under this cap will
> be a screw that adjusts endpoint.  You do this one first, however 11 kcs will
> require removal of a turn from the endpoint adjustment coil.
>
> This will require opening of the PTO to get at the coil.
>
> Last time I did this I just made a new coil with one less turn and replaced the
> old one with the new.
>
> After removing a turn, the PTO should have new life and you'll be able to get
> 1000 kcs in ten turns.
>
> The thing will drift in a predictable direction (I'll avoid the use of words
> like "long" and "short" because this list has long and short word police,
> equally rabid about "their word"  :-)
>
> What I do is give the thing about 1000.5 to 1001 kcs in ten turns to avoid
> having to go back in there within the next 12 months.  One extra kcs should
> last you a few years, afterwhich the thing should be right on the money (like a
> stopped watch I guess!).
>
> Linearity adjustment is a whole nother project.  You can pull down some
> instructions from Chuck Rippel's website.
>
> Cheers
>
> Tom N5OFF
>
> --- Philip B Atchley <[email protected]> wrote:
> > Hello all.
> >
> > Well, I still have Dons R-390A on the test bench being worked on.  This
> > is the receiver that has the Cosmos PTO.  As it turns out this sucker has
> > the endpoint out by about 11kHz, and I thought the 6kHz on my Collins PTO
> > was terrible before I corrected it!
> >
> > Anyway, I read through the Cosmos setup that I downloaded and it looks
> > like a REAL pain in the rump to align.  I 'thought' that there might be
> > an endpoint adjustment separate from the linearity adjustments and so
> > removed the cap screw.  Apparently this is NOT the case.  But I'll ask
> > anyway.
> >
> > QUESTION:  Is there a way to set up the endpoints separate from the
> > linearity adjustments?
> >
> > 73 de Phil  KO6BB
> > Loving home provided for wayward Boatanchor Receivers
> > [email protected]
> > Merced, Central California
> > 37.18N  120.29W  CM97sh
> >
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