[R-390] Cosmos PTO

[Tim Shoppa]

<mfisch at kent.edu> wrote:
> I know there is a lot about the Cosmos PTO out there, but nerves have
> got the best of me.  I want to adjust the end point (out by about 1 kHz)
> and I took off the screw to adjust the end point, but the end point
> adjustment screw looks like a spanner nut with a rubber center.  Do I
> just take a 1/8 inch blade screwdriver and have ho or is there something
> I need to be careful of?  I was expecting a slot and it looks like I
> should stone a screwdriver to have parallel sides.  Is this the case?
> Thanks in advance.

Well, two months ago I didn't know what a Cosmos expert was, now I is one!

There are three "holes". The endpoint one is the one that is
partially obscured by the transformer can. Removing the can
might help get you access (especially if you have a stiff-bladed
driver). BUT... I think there is "hot" wiring inside the transformer
can so be careful if you do so. If you do not remove the transformer
can you can use a metal screwdriver without fear.

The one next to the endpoint hole reveals all the little linearity
adjustment screws. (I bought the 4-flute spline driver for these
from McMaster, let me know if any of you need the official McMaster
part number.)

And there's a third hole that reveals the thermostat set point.
This is a BIG (in comparison) brass screw.

Not sure what a "spanner nut with a rubber center" is, but the
endpoint inductor has a brass three-wing section that has an
external nut which can tighten down on the brass adjustment
screw. I think the purpose of the three-wing section is that it
is adjusted to minimize wiggling/backlash of the internal brass
adjustment screw. The brass screw is attached to the slug.

If you find you do not have enough adjustment range, you probably
have to open to the PTO can and adjust the turns on the inductor.
Others talk about removing whole turns, but for mine I found that
removing half a turn (reversing the direction of the winding so it
went from 2.75 turns to 2.25 turns) was the best choice. In my
case removing a whole turn took me too far in the direction of
increasing the span. But removing half a turn got me in the
"sweet spot". Since you're only 1kHz off in endpoint, maybe you
don't have to do this surgery. But if you find yourself with the
brass screw all the way inside the three-wing clamper, or sticking
out so far it would interfere with the threaded cover, then maybe
it's time.

Tim.