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Servo amplifier substitute?

Started by AAnnillo, April 21, 2022, 10:25:57 AM

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April 21, 2022, 10:25:57 AM Last Edit: April 21, 2022, 10:26:53 AM by AAnnillo

Am attempting to operate and interface a Sperry RMI (Model C-6E) for use in my sim and am experiencing challenges in getting the compass dial to move.
Both needles move perfectly with their separate switches engaged.
I have the pin out sheet for the unit as well as the Boeing 727 wiring guide and have tried many power/X Y Z synchro hook-ups all to no avail.   There are Control Transformers, Transmitters a motor-generator (with 3 power requirements) and I just cannot get the compass to rotate.

In the wiring guide, it shows connections to the unit via a servo amplifier (which I can purchase via EBay) connected to a flux valve (already purchased—-strictly for the  sake of  getting a clearer understanding). I'd need 2 amplifiers...one for Captain's side and the other for 1st officer's side.
I can get the motor-generator to work (spin) by connecting the 26VAC leads to my 26V/400Hz power supply but any combination of adding hot and common connections and X Y Zs to transmitters or control transformers has proved fruitless.  This compass will not move.   The wiring guide shows a transmitter coming from the gyro rack to the servo amplifier then to the unit; and this will be duplicated for a standard transmitter down-the-road.

Can you think of any alternative method(s) for driving the compass dial or should I just buy the servo amplifier?

I had thought of retrofitting a NEMA 8 stepper motor to direct drive the compass reel/gearing and have a gut feeling that this is the only option as of right now.   The problem with this option is the difficulty in mounting the stepper inside the unit on the interior bulkhead. 
I'm open to suggestions.

Thank you very much for any guidance.


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