[TowerTalk] Telrex rotator

[john at kk9a.com]

I had one of these rotators and I never had an issue which was a big step
up from the Hy-Gain HDR-300 that it replaced. Sadly the resale value is
poor and I almost gave it away when I switched to using prop pitch
rotators.

If it were me, I would replace the selsyn with a potentiometer and then
almost any control box would read the direction, especially a Green Heron
where you could calibrate the indication. The remaining issue would be
supplying 120v to the motor. This could be done with relays activated by
the low voltage control box or perhaps W2FU has a better solution.

John KK9A



From:	Martin Sole hs0zed
Date:	Fri, 16 Nov 2018 12:04:18 +0700


Hi,

I'm restoring a Telrex A3695RISX rotator. It's quite a monster but if I
can figure out a way to use it I think it's unlikely I would ever need
anything bigger, 1/3hp reversible AC motor, dual worm reduction gearbox,
chain drive to 3" output shaft and it weighs about 125 lbs, around 57kg.

I have no control box which poses a small problem. Wiring to the motor is
straightforward enough though I think the limit switch arrangement could
be handled better.

It uses a selsyn for position indicating. In this case actually a General
Electric Selsyn Control Transformer 2J161. This is marked 57.5-57.5 V
400CY. The device is working in that I can get the three outputs from the
stator winding when I excite the rotor winding, all three stator outputs
rise and fall with rotation so I'm pretty sure its good.

The problem is what to do at the other end. Without a matching selsyn, not
something I expect to ever turn up around here, I am wondering how I might
be able to take the selsyn outputs and interpret them by some other means.
My understanding is the 3 stator outputs are AC voltages varying in
amplitude and with a fixed phase relationship in order to produce an
unambiguous value related to absolute position. I'm not 100% on this yet
though. They are in a delta configuration though so I'm thinking anything
I do first needs to make them Y configured

What are my options?

I had thought about an I2C compass module but that will entail placing
some other conversion hardware at the rotator to convert to something like
RS422. Any other thoughts. Just looking for ideas to think of what might
work well enough. Ideally keeping the selsyn as it's all purpose built
around that.

Martin, HS0ZED