[R-390] Non-Linear PTO

[Forrest Myers]

> I had a problem with my Progressitron PTO where it had a bad spot right
> around 100khz Where it was suddenly almost 2khz off, depending on the
> direction of tuning. Tuning uphill, it was fine. Tuning downhill, it went
> bad at about 105khz and got back on track at about 80khz. Took the PTO
apart
> and found it to be unrepairable due to the sharpness of the change in the
> stack at that point.
> Decided to get another PTO.
> Bought a junker from Fair Radio. When it arrived, I took a look at it and
> didn't have much hope. It was very beat up, dented and dirty. Took the
outer
> can off to see if the dents reached the inner can and found that they
> didn't. The shield on Z702 was badly dented and leaning at about a 10
degree
> list to port. I took the cans and brackets off and gave them a good
washing.
> Decided to to some body work on the Z702 can and got it back into fair
> shape. Bent the works inside the Z702 can to where they stood straight up
> again. Noticed that T701 had never been soldered in! Wonder how it ever
> worked reliably. Probably never did. Soldered T701 in. The output co-ax
was
> in bad shape and was almost cut in two in a few places. Replaced the
co-ax.
> Made up a test jumper cable and hooked the PTO up to power to see what
would
> happen. Hooked a frequency counter to the output and fired it up. The PTO
> came up without any smoke and was on a reasonable frequency. Turned the
> shaft and it seemed to be very stable. Maybe it was going to work!
Adjusted
> the PTO to put out 3.4550 mhz and powered it down.
> Installed the PTO in R-390 a Capehart SN #557, did the end point
adjustments
> and it's just fine!
> The linearity is within spec and seems very stable. Hope it keeps working!
> I'm keeping the old Progressitron for a backup but will probably never use
> it because of the bad spot in its tuning range.
>
> Keep em glowing,
>
> Forrest Myers
> AG4ND