[R-390] Question on COSMOS PTO

[Tim Shoppa]

> 1. Zero beating against the calibration 100Khz signal at x.000 after
using
> the zero adjust knob to be exactly at x.000, I noticed that if I
either dial
> up or down from this calibration spot, coming back to this mark, I'm
always
> either +/-100Hz off depending on the direction I'm turning. Is this
what you
> call backlash or hysterisis?

This is backlash, and it is probably in the gears coupling to the
counter
mechanism.

Assuming that all the springs are in place and tightened, the worst
offender
in the chain is the bevel gear that comes right before the counter. This
can be adjusted a little bit (setscrews) to tighten it up. If you watch
the bevel gears (either looking in from top/bottom or with the front
panel off)
you can see and feel the backlash as you wiggle the front knob.

> calibration. Am I approaching the design limit being off +/- 100Hz on
the
> calibration mark?

Pretty much. While the bevel gears can be squished into each other
tightly this
still doesn't remove all the backlash (and it certainly isn't "right" in
terms of
mechanical operation, you quickly start noticing a lot of rubbing
friction from
those gears as you tighten things up.)

See my thread from last month about a different problem, a
"squirrely PTO", which I had to tear down the entire PTO for.

Tim.