8mm Forum: Alternate Main Motor for the GS 1200

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Topic: Alternate Main Motor for the GS 1200

Thomas Knappstein
Expert Film Handler

Posts: 124
From: Erwitte, Germany
Registered: Oct 2017

posted November 14, 2017 09:49 AM

First I will say that its very interesting to read here in this Forum. So also the older Posts from the early Days of this Forum special of the Elmo GS 1200.

I do not know everything and so it is very importand to learn more about this terriffic Machine.

But now I will give something back to all GS Owners which have problems with the Main Motor. In the Past I have wrote about this and I cut the old Main Motor to get the Tachometer Coil and Disc to put it on the alternate Dunker or Crouzet Motors. So than the old Elmo Motor was destroyed and can´t get back to use.

Now I had a Machine where was no Motor inside. So there was no Coil and Disc. In the Service Manuel of the GS I read that the Generator must give 24 Pulses at one turn. So I made a Disc of 0,8mm Aluminium drilling 24 Holes in it. Than take a IR Sensor to pic up the Pulses from the Holes. The + Voltage for the IR Sensor I get from the 6V of the Sync Conector on the back Side of the Machine. The Ground is comming from the Motor Tacho Conector of the Main Board. And the Pulse input too. With a few resistors this is working as well as teh original Elmo Motor. And this High Quality Dunker Motors with ball bearing on both Sides have a very long life to show many Films.

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Phil Murat
Jedi Master Film Handler

Posts: 671
From: Villeneuve St Georges, France
Registered: Dec 2015

posted November 14, 2017 10:18 AM

Hi Thomas,

Very good work ! [Wink]

I keep the idea "on left". When I get more time I make a test with a classical "Arduino" infra red sensor (5v instead of 6v). There are cheap and give a very good square signal.

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Thomas Knappstein
Expert Film Handler

Posts: 124
From: Erwitte, Germany
Registered: Oct 2017

posted November 14, 2017 11:31 AM

This IR Sensor came from a german elektronic seller and it cost 0,96 Euro.

The Square Signal is not so importand because the original tacho has a Sinus Wave. This Wave is cutting their Tops by the two Diodes on the Main Board of the Elmo. Than it looks like a pseudo Square Signal. Very importand is the Time Base when the Waves are shown on the Scope. This is only right with 24 Pulses on one turn of the Motor Shaft.

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