[R-390] Re chirping CW and low audio plus strange PTO problem.

[mikea]

On Thu, Jun 17, 2004 at 07:57:57PM -0400, Forrest Myers wrote:
> Well, today I took the PTO apart. Inside it looked like a new one. All the
> lubricant was still very moist and the spring on the stack follower was nice
> and strong. I figured out the problem but didn't fix it. It appears that the
> PTO was defective when manufactured and when it was linearized, it was done
> only while tuning uphill.

> The correction stack has a very sharp bend right around the 100khz point. I
> checked both rollers as they passed the sharp bend and they both followed
> just fine. Looking closer, I noticed that there was a slight gap between the
> wafers in the stack. Looking even closer, I noticed that, when tuning
> uphill, there was so much pressure on the wafer at the peak of the bend that
> the wafer actually bent under the load and straightened out after the roller
> passed it. When tuning down hill, the wafer wasn't under much pressure at
> all and didn't bend at all, thus the difference in the linearity between
> tuning up and tuning down.

> I didn't see any easy way to fix it so just put it all back together. One
> nice thing is that the rig still works and the linearity didn't change,
> whew! Guess I'll just live with it unless anyone on the list has a way to
> fix the problem.

> I suppose, I could change the wafers such that it tuned correctly going
> downhill and then fill the gaps between the disks with epoxy or something so
> that they wouldn't bend while tuning uphill. Sounds like a lot of tedious
> work to me.

Well, the easiest way to fix the problem would be to get a "new" (to
you, at least) PTO, from Fair or someone who's parting them out, or 
from one of the R-390/R-390A fixers. 

Good luck, whatever you choose to do. 

-- 
Mike Andrews
mikea at mikea.ath.cx
Tired old sysadmin