[R-390] COSMOS PTO, starting over again.

Sun, 13 Jul 2003 08:49:56 EDT

In a message dated 7/13/2003 2:02:53 AM Eastern Daylight Time, 
[email protected] writes:

> Todd
> Well maybe I was doing it wrong.  You have to take the can off, then loosen
> that clamp screw in the back and then nudge the one slice of the stack you
> need to adjust, then tighten the screw again, then put the can back on, then
> check your frequency, and repeat those stepst every 25 khz... seemed like
> the stack would squirm around whenever I loosened that clamp screw throwing
> a bunch of them back out of alignment, and I'd have to repeat it all
> again... or if I tweaked one slice, it would mess up those either side.  If
> there's a better way I sure wouldlike to know.  I have heard the rumor that
> Collins had a few very unique people locked away who did nothing but PTO
> calibration.
> 73 N4BE

Jim, thanks for all the info AND PICTURES you posted on your web pages on 
repair and calibration of the Cosmos PTO. Now I have a much better understanding 
of the inner workings of the Cosmos!  When I recalibrated the Collins PTO with 
the corrector stack, what I did was loosen the corrector stack holding screw 
just enough so that with some force I could slide the adjustment disks but not 
so loose that the corrector stack would loose its shape. Instead of trying to 
slide one disc at a time I would gently curve the outline of the discs at the 
correction point. I checked mine every 100 KHz but I'm sure it would take 
more time and be more tedious if someone wanted to check every 25 KHz. The 
linearity seemed very good so I didn't bother to check every 25 KHz. Mine was off a 
half a KHz or so between about 3 or 4 100KHz checkpoints in a row so it was 
not a real tedious job. I can see the benefits of the Cosmos design - as long as 
it has not been abused or the ring damaged along the way. I can see how 
someone not familiar with the Cosmos might try to screw those linearity adjustment 
screws in by mistake thinking it was the end-point adjustment. I bet that is 
how some of them got broken or damaged in the past. Thanks to Al for posting 
the address for getting a copy of the degree wheel - a handy item!  73 Todd 
Roberts WD4NGG.

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