[R-390] PTO Problems

[Flowertime01 at wmconnect.com]

Jon,

You touched on adjusting the corrector stack in the VFO.

>From old war stories YMMV.

Once you get the end points adjusted the VFO is likely to be linear.

As you look down the adjusting stack it likely has a nice S or C curve.
The curve is not necessarily symmetrical from end to end.
But the curve should be nicely done with not sudden jumps.

The stack is likely "sealed" with some varnish.

If your end points and if the linearity is not off by more than 100 hertz at 
any 100KHz cal tone within a MHz band then just live with it.

Never having had a good jig to help align the stack doing it has always been 
a venture of trial and error.

Get the end point spread set first.
Remember what your stack curve looks like.
The disassembled. cleaned, reassembled, tuned tightened and resealed stack 
will look very much the same.
Take the stack all apart and clean out all the old varnish used to help keep 
the stack 
aligned after it was adjusted during assembly.

Run ample amounts of Vaseline on all the plates in the stack to stick them 
together.

Reassemble the stack and just snug up the bolts.
Squeeze out the excess Vaseline and wipe up all that is sticking out and all 
that is any where except between the plates.

Using you sticks, pliers, levers and other improvised tools, get the stack 
straight and about center from end to end.

If you get the bolts to tight you cannot get easy adjustments.
If you get the bolts to loose the stack will move out of alignment in spite 
of the Vaseline.

Now it is a process of test, and adjust until yo are happy.
Leave the Oldham coupler on the shaft as a knob and indicator.
Mark the coupler to the face plate.

At a 1/2 turn you can get an exact alignment at each 50Khz.
You then adjust the stack plates between the 50Khz points for a "smooth" 
curve.

When you are happy with the whole stack you tighten up the stack bolts and 
test the whole curve again.

The shaft position may change at the end points.
The total spread should stay the same from end.
Using the stack to trim the end points is not the way to go.

The stack is to provide a very linear change of the VFO from end point to end 
point.

Once you get the stack reset and tight, clean out any Vaseline.
The stack can now be resealed along the outside edge with varnish "glue".

In (68- 75) We talked about doing the stack with slow drying varnish or paint 
between the stack plates. The velocity of the wet varnish would hold the 
plates, not dry before the adjustment was complete, form a seal after adjustment 
was complete to hold the alignment. We never did it this way. We only did this 
stuff because we had the time to mess with it. Back then we just did the paper 
work and got a new VFO out of the box we received from the supply room.

Roger AI4NI

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