8mm Forum: ELMO GS 1200 slow down

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Topic: ELMO GS 1200 slow down

Lance Alspaugh
Expert Film Handler

Posts: 152
From: Los Angeles, Ca
Registered: Jun 2003

posted October 18, 2007 05:33 PM

Gentlemen,

Have experienced a sudden problem with the GS. Speed is irregular and doe not stay consistent. Have tried changing to new motor and that failed to solve the problem. Should I be loooking to the Mother Board now as the culprit. I have an extra one to put in if that is the concensus. Any help is appreciated.

LA

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted October 19, 2007 09:04 AM

I had exactly the same problem on a GS here in the UK. I put the motor in my own machine and it ran very smoothly and cool but in its original machine the motor was variable and slow and also ran very hot. The speed control switch made little difference and there was virtually no fine speed control.

I replaced the speed control board but that made no difference. I then checked the diodes D306, 307 & 308 on the main board for dry joints but this was ok.

I then turned the shutter by hand with no belt attached to the motor and this felt quite tight.
This turned out to be caused by someone using the wrong grease which had gone hard and also some of the cogs had no play between them. This machine had previously been stripped down to have a 2 blade shutter installed so I suspect this is when this all ocurred but has taken years to show itself.

The machine was stripped down and all the cogs were cleaned etc. The machine was reassembled making sure the cogs on the adjustable plates were adjusted to allow some free play. Once regreased with the correct grease the machine was fired up and all once more ran correctly.

I think that once you get a certain torque on the motor the speed control circuitry gives up as it ramps up the voltage to try to run the motor at the correct speed but eventually runs out of wick as there is no more voltage to supply. This leads to a motor which runs extremely hot and would have certainly failed eventually.

This has led me to wonder if this sort of problem is what causes motor failure on these machines. In this case failure was prevented.

So there are a few things to check especially as you have confirmed that the motor is OK.

Check if the speed changes significantly when you adjust the speed switch and that you get a definite change in speed with the fine speed control.
If as I suspect you dont then run the motor with the belt off. If you now get full control of the motor with the switch and speed control then I think you are looking at a mechanical problem (as above) and not an electrical one.

I hope this experience helps you or someone else at a later date.

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Lance Alspaugh
Expert Film Handler

Posts: 152
From: Los Angeles, Ca
Registered: Jun 2003

posted October 21, 2007 06:26 PM

Hey Kevin,

Your analysis seems to have helped this problem. I think maybe I need to have the machine overhauled as you mentioned, but I have temporarily at least loosened the assembly's with lube and oil. It at least now runs at a consistent speed with a cooler motor. I think still slightly below normal speed, but greatly improved. You ARE Mr. Elmo once again! Thanks very much.

LA

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted October 22, 2007 06:33 AM

This is becoming all to common a problem.

Maybe I need to do an item about lubricating these machines. [Smile]

It's better to remove the cogs and soak all the old grease off first before re applying fresh grease. The Brass worm drive should also be cleaned. I use an old toothbrush with some white spirit and turn the shutter by hand.

Any extra load will cause the motor to not control properley and run excessively hot with eventual failure [Frown]

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Paul Adsett
Film God

Posts: 5003
From: USA
Registered: Jun 2003

posted October 22, 2007 06:59 AM

Hi Kev,
I think a post on the cleaning and lubricating practice for the GS1200 would be invaluable, particularly if it includes a listing of the currently available recommended lubricants (if there is a consensus on that!)

--------------------
The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj

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Graham Sinden
Phenomenal Film Handler

Posts: 1131
From: Kent, UK
Registered: Aug 2005

posted October 22, 2007 07:15 AM

I agree with Paul on this. Everybody keeps mentioning "Lubricate the cogs and claw with the correct grease", BUT WHAT IS THE CORRECT GREASE??.

I want to lubricate the claw on my GS800 but Im not sure what to use? [Confused]

Also can nylon cogs crack if you use the wrong lubricant?

Graham S

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted October 22, 2007 07:59 AM

I would be very surprised if your claw needed lubricating. Elmo used a really thick graphite based grease on the cam mechanism and also a small piece of sponge to keep the unit well greased up.

I havent to date seen a cam assay which needed regreasing.

Yes plastic cogs can crack if the wrong type of grese is used. The plastic (Nylon) goes britle.

I use a lube which Craig Hamilton got for me. Its designed for use on plastic etc and is brilliant Stuff and blue in colour.

Craig, name please.

If you download the GS manual from the manuals section the recomended lubes are listed. Most have now been replaced by more modern equivalents.

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Graham Sinden
Phenomenal Film Handler

Posts: 1131
From: Kent, UK
Registered: Aug 2005

posted October 22, 2007 11:23 AM

Hi Kev,

The only reason I said that is that my GS800 is not as quiet as it should be and im just thinking it needs a lube inside as I havent got round to doing it yet. my GS800 is certaintly noiser than my GS1200 and ST1200.

Graham S

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted October 22, 2007 11:30 AM

Hi Graham, I would start with the cogs etc first and take it from there. Im not saying the cam doesnt need attention but I would think it unlikely. See if doing the cogs and worm help reduce the noise.

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Graham Sinden
Phenomenal Film Handler

Posts: 1131
From: Kent, UK
Registered: Aug 2005

posted October 22, 2007 04:35 PM

I'll give it a go when I get the chance and I find some good lubricant. Ive got some yellow grease labelled up RL2. I will look at the GS1200 service manual first.

Graham S

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