8mm Forum: Sankyo 600 Can motor brushes or springs that hold them effect how much current the mo

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Topic: Sankyo 600 Can motor brushes or springs that hold them effect how much current the mo

Phil Mitchell
Expert Film Handler

Posts: 144
From: Melbourne, Australia
Registered: Aug 2013

posted January 17, 2015 08:54 PM

Hi all,

I have my working Sankyo 600 now, but even though speed board appears okay, it will not change to lower speed by Trim pots or frame rates switch, My mate who is a electronics nut check this speed board and we have even increased ohms and Watt of the resistor of the one that that went catsus when board came in contact with the nut that holds the transistor onto heat shield, that transistor was also replaced,

My mate now feels motor is drawing too much current and I am wondering if there is anything I can check in relation to the brushes and the springs that hold them in the motor?

Can the brushes effect the current draw of a DC motor?

BTW anyone want the circuit drawing my mate did for speed board, let me know.

Cheers
Phil

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted January 17, 2015 09:30 PM

I'd think if you used the original springs and used brushes of the correct dimensions then the current should be just fine.

If you had to pound them in with a mallet, NOW we're talking!

Have you been able to measure the current?

--------------------
All I ask is a wide screen and a projector to light her by...

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Phil Mitchell
Expert Film Handler

Posts: 144
From: Melbourne, Australia
Registered: Aug 2013

posted January 17, 2015 10:16 PM

Hi Steve, thanks for reply.

Yes you had same thought I did, when my brother and I were first testing what could be causing the problem when this unit just stopped running, one thing we did was check brushes and springs for motor and no we didn't replace with o springs, being wiser in hindsight now I look at the springs we used, they are a bit longer, couple of mm at most and a copper type, not ah what ever spring would be greyish colour. Silver I guess.

I also wonder now if the brushes themselves were not put in the way they were, e.g the worn ends, would that effect current draw I suspect so, as I understand these motors.

Going to put orginal springs into motor and have also the worn looking end of brushes towards inside of motor.

Now as for question have I worked out current, yes.

It is drawing 500ma DC, using formula my mate gave me, that works out to in Wattage, 12V x 0.5am = 6 Watts.

Fortnautley I bought another Sankyo 600 since this older one played up for not much $$ and did same current draw on it.

From it I got 12x .65a = 7.8 W on 18fps and on 24fps 12 x .775a = 9.3 Watts.

Thanks
Phil

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Steve Carter
Master Film Handler

Posts: 282
From: Bristol, UK
Registered: Apr 2015

posted April 29, 2015 05:36 AM

I purchased some brushes which were of a similar size for my Bell & Howell DCT, I sanded them to correct size with some very fine emery paper, I then replaced the springs with the original Bell & Howell ones, and it ran as good as new. The Sankyo has the same motor I believe as the Bell & Howell.

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