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Re: [TowerTalk] Telrex rotor Selsyns

To: <>
Subject: Re: [TowerTalk] Telrex rotor Selsyns
From: Jim Lux <>
Date: Sat, 27 Jan 2007 09:47:42 -0800
List-post: <>
At 07:27 AM 1/27/2007, you wrote:
>The synchro used by Telrex is a 400 Hz synchro run at lower than rated
>voltage at 60 Hz.  It also has an unusual small diameter threaded shaft.

running 115V 400Hz synchros at 24 V 60Hz is pretty common.  Just 
makes a bit of a buzzing sound under load, and gets a bit warmer than 
normal (and, the torque characteristics are different.. but if all 
you're doing is driving a pointer, it might not make much difference)

The small shaft is definitely a problem.

>I suspect you will not be able to find a direct replacement on the
>usual hamfest or ebay market.

I would expect you could find one with the correct outside housing 
size, since they're all pretty much standardized, and I imagine that 
Telrex designed it originally around readily available mil surplus parts.

As you say, though, the shaft, or the terminal configuration might 
prove to be a problem.

The "catalog surplus" places (like C&H) charge about $50 each for run 
of the mill, common sizes.
400 Hz ones are cheaper, of course.

>   If a new direct replacement is available,
>its likely to be very expensive.

You betcha.. probably in the $200 range.

Another source of these things is places selling marine 
equipment.  They're used for remote indicators and such.  They're 
also used in some radars as an encoder for the antenna position.

>   Perhaps rewinding your existing
>synchro or redesigning the control box to use more readily available
>components are the most practical solutions


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