8mm Forum: Pathe Gem, rewiring the speed control

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Topic: Pathe Gem, rewiring the speed control

Vic Newey
Film Handler

Posts: 41
From: Worcestershire, England
Registered: Dec 2015

posted October 17, 2017 09:37 AM

I've rewired the resistance useing the wire taken off the speed control of a now defunct Pathe H.

The problem is it now it barely runs at any speed,even pushed over to maximum it goes too slow to run a film. What did I do wrong ?

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted October 17, 2017 09:58 AM

Vic
It's quite probable that the two motors run at different voltages.
By the way - Please read my PM.

--------------------
Maurice

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Vic Newey
Film Handler

Posts: 41
From: Worcestershire, England
Registered: Dec 2015

posted October 17, 2017 10:17 AM

Hello Maurice, the forum won't let me email you, I get :

Sorry, either the user or the board administrator is blocking access to this email address.

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted October 17, 2017 11:05 AM

Vic
Try again.

--------------------
Maurice

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Terry Sills
Phenomenal Film Handler

Posts: 1423
From: Weymouth,Dorset,England
Registered: Oct 2012

posted October 17, 2017 11:25 AM

Vic
It's quite obvious that the wire you have used is of a higher resistance value than the original. Hence no speed when you activate the motor. You need to take a section of the original wire and get it tested to find its resistance value ( unless you have the facility to do it yourself). I wouldn't have thought it would be a problem to get some wire of similar resistance.

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Vic Newey
Film Handler

Posts: 41
From: Worcestershire, England
Registered: Dec 2015

posted October 17, 2017 11:31 AM

I've just bypassed the speed control to see what happens and the motor still runs slow, it's got the correct belt newly fitted, if I remove the belt the motor goes full speed, the mechanism turns freely enough so no idea what's happening here

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted October 17, 2017 11:31 AM

Vic
Received your PM. I understand your comment.

--------------------
Maurice

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Terry Sills
Phenomenal Film Handler

Posts: 1423
From: Weymouth,Dorset,England
Registered: Oct 2012

posted October 17, 2017 11:36 AM

Vic
Did you ever have the Gem motor running before you attempted to rewire the speed control?

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Vic Newey
Film Handler

Posts: 41
From: Worcestershire, England
Registered: Dec 2015

posted October 17, 2017 11:38 AM

Yes, it did run & project but the speed control didn't work properly because the resistance wire was broken in several places

I'm just wondering how free the motor should turn with the belt off, it's perhaps not as free as I would expect so maybe under load it struggles. When I ran it when I first got it it worked o.k with a couple of films but with another it was far too slow and that's why I'm trying to fix it

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Terry Sills
Phenomenal Film Handler

Posts: 1423
From: Weymouth,Dorset,England
Registered: Oct 2012

posted October 17, 2017 11:54 AM

I have had problems in the past with the 'correct ' belts. They are very thick and tend to put too much strain on the motor pulley, especially if they have gone out of shape over the years. I personally use nitrile belts which I make up myself from lengths of it which can be bought online. The original belts put unnecessary strain on the motor mounts which put the motor out of true and then causes slippage and other problems. The motor mounts are of rubber and degrade over age and they may also need replacement.

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Vic Newey
Film Handler

Posts: 41
From: Worcestershire, England
Registered: Dec 2015

posted October 17, 2017 01:23 PM

I got the belt from Grahame Newnham so it should be the correct one, I'm more convinced the motor should turn a bit easier, are the motors on the Gem sealed bearings ?

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Terry Sills
Phenomenal Film Handler

Posts: 1423
From: Weymouth,Dorset,England
Registered: Oct 2012

posted October 17, 2017 03:39 PM

Vic
From memory I believe they are but you may be able to lubricate somewhat by placing drops onto the motor spindle. Personally I don't think the motor is the problem. I would check out the replacement windings on the speed control. With the belt removed the motor is not under load so it will run well but the real test is when it is under load with the belt on. All I can say is that when I replaced the original belt with a much thinner nitrile belt it made a huge difference to the performance.

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Vic Newey
Film Handler

Posts: 41
From: Worcestershire, England
Registered: Dec 2015

posted October 18, 2017 03:33 AM

Terry,

I've temporarily bypassed the speed control so it has no effect on what is causing the slow speed, I'm thinking now that perhaps there is a voltage drop to the motor

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Terry Sills
Phenomenal Film Handler

Posts: 1423
From: Weymouth,Dorset,England
Registered: Oct 2012

posted October 18, 2017 03:48 AM

Well if you have the means you can check that out, but my guess is that you are thinking too deep. Try the simple things first. If you remove the belt and the motor races and then you replace the belt and it is slow, then that should tell you something. Either there is slippage of the belt, or it is too tight, or the motor is at fault. Have you checked the motor alignment? Is the inching knob central in the front plate aperture or is it pulled to one side (towards the lens). If so the motor mounts need looking at.

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