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Chris Lange

Arri S 16mm camera, 400' magazine troubles

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Everything else on the camera works just fine, except I can’t get the 400’ magazine to work.  
I have tried two different torque motors on the magazine.  I use a 8.4V-5ah battery made by a company called Cine60.
Can you offer suggestions?  Do I need to modify my torque motor?

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The best I can offer; clean all contact points, on the camera where the magazine makes electrical contact. all points in the magazine and on the motor.  If possible, run test wires to the motor with the 8.4 volt battery to see if the motor runs. There is a wire inside the camera that could be broken.  The torque motor brushes may be too dirty.  The torque motor could be a 12V motor and is not getting enough volts or amps. Did the torque motor work in the past or is it new.  Less likely is very dirty bearings in the magazine which could prevent the magazine from working.  More information would be good.

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Thanks for the info!  I bought two torque motors on ebay (from same seller), and they both didn't work.  It might be the wire inside the camera, but I will start cleaning and testing points, as you suggest.

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eBay is really a roll of the dice, I have purchased good quality working items and items that did not work at all and required quite a bit of repair. Test each motor first, they could both be bad, but I think that may be a low probability. See if you can move any of the moving parts of the motor by hand, they could be rusted or corroded in place.

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"Your camera and magazine might need to be connected by a ground wire."

I agree with Jean-Louis's above statement.
According to Arri back in the day, the torque motor was grounded to the magazine when locked into place on the mag. When the magazine
was attached to the camera, the magazine was supposed to be grounded to the camera.
But, back then there must have been occasional problems with grounding the torque motor, so Arri came up with a sure fire solution, ground the torque motor
directly to the ground on the battery. This was accomplished with a 'ground wire' as Jean-Louis recommended.
When you purchased a 16 S power cable from Arri, it came with a grounding wire for the torque motor.
One end of the grounding  jumper cable was plugged into the ground side the  power cable, and the other end was plugged into the torque motor via the silver receptacle shown in the pic below. 400 ft & 200 ft torque motors have the same grounding connection.
The red arrow points to the positive power pin in the magazine that makes contact with the camera.
When the cameras were newer, it was rare to use the jumper cable (my experience). I used 4 torque motors and never had problems, or needed to use the cable.
Most users removed that little cable from the power cord and set it aside. If you were just using 100ft loads, you didn't need it. Then those little cables
would eventually disappear. I've seldom seen them in 16 S kits for sale. 
Arri listed the ground cable in a 1962 price list: "Special Ground Connection Cable (Replacement); goes from main Cable to Torque Motor".
It was still listed in a price list as late as 11/1980. I don't have the separate instruction sheet for the 400ft mag and torque motor.
Very little was said by Arri about this ground cable. There are no ad pictures that I've seen showing this little cable in use. 
Applying 8.4 volts to a torque motor that was modified for 12 volts would just make the torque motor run slower. If the circuit supplying power to
 the torque motor, and then to ground, is complete, it would still run.

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Thanks Charlie - this info helps, nice detail!  I certainly don't have that Special Ground Connection Cable, but maybe I can track one down.  I will look into the issue further, so thanks, but for now it will be 100ft rolls.

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I ended up checking voltage at the small button contact on the (camera) magazine port, with the camera run switch depressed and connected to power.
I checked the voltage with a digital multimeter - this little button contact did not have voltage.

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there are others who are much better at this than me, however, I have a photo of what I believe is the wire you have tested.

The red arrow is the exterior contact point I believe you tested. The green arrow in the photo indicates the location and path of that wire.

The purple arrow is the terminal point which is soldered or attached by a screw to the power switch(140.jpeg and 159.jpeg)on the inside of the camera. I think this wire could be shorting out at the red arrow contact point(I seem to remember this is an insulated terminal point. ),the wire could be compromised, or it could be disconnected at the power switch.  There may be other solutions to this which other members have better knowledge.


1 - 1.jpg



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Hi Michael,

Thank you for these detailed photos!  This seems right.  I think your assessment is getting me closer to a solution.



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