[TowerTalk] Telrex rotator

[Martin Sole]

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