8mm Forum: GS 1200 Main Motor

This is topic GS 1200 Main Motor in forum 8mm Forum at 8mm Forum.

To visit this topic, use this URL:
https://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002765

Posted by Robert Tucker (Member # 386) on April 29, 2007, 11:07 AM:

Hi Kevin,

I finally got around in taking out the main motor which you will hopefully test for me. Please note i did test this again when i took the motor out by just putting back the wired plug. It starts when you press play on the projector but stops straight after you have pressed play.

Could this be the motor telling me that it is actually on it's way out? or is because it is not around the motor belt in the machine. And if so how can i obtain another motor?

I did note that from taking out the main motor it has the date of 9th Nov 1978, i assume this is when thr motor was made?

Please let me know when you are free this week so i can bring along the motor into work and meet up.

Lets hope it can be fixed??? [Mad]

Thanks,

Posted by Kevin Faulkner (Member # 6) on August 10, 2007, 07:24 PM:

Well this problem has taken a while to solve but it has now come to a good conclusion.

I visited Robert and had a good look at his motor problem which did have me baffled.
Robert's GS had no motor control at all. When the motor was in the machine it ran very hot to the point where it was too hot to handle [Eek!]

and the speed control on the GS had no effect at all.

If the motor was removed from his machine it cooled down and there was some control.

I took the motor home along with the speed control board and striped the motor and gave it a good clean up.

I then put the motor in my own xenon machine and it ran faultlessly. I put Robert's speed control board in my machine with his motor and again all ran with no problems. Robert's motor also ran a lot cooler in my machine.

So what was the problem, what was causing this very erratic behavior?

I spent another day at Robert's house and closer inspection found that the cogs that drive the top sprocket were very tight. There should be some play between all the cogs and in this case there wasn't any play at all.

At this point I stripped down and removed the whole shutter assembly. All the cogs were cleaned in spirit as was the shutter bearings on the main drive shaft.

The machine was re-assembled making sure that there was correct play between all cogs and lubrication was applied where necessary with the correct grease.

When the machine was started there was complete control of the motor at both 18 & 24fps.

The moral of this story is that if a machine is stripped down to put a 2 blade shutter in it as was the case here before Robert bought it that when reinstalling the cogs etc attention is paid to the free play in the cog train and that the correct greases are used so that they don't go hard.

Any undue friction will result in a motor which will eventually burn out and also cause the diodes on the main board which are in series with motor to over heat and cause erratic behaviour.

I think between us we saved yet another GS [Smile]

Kev.

UBB.classic^TM 6.3.1.2