Arri-S 16mm slows down on long shots?

[Carl Elsaesser]

Hey all, 

I just bought a new Arri-s with a bayonet mount to replace my old Arri-s with three standard mounts. I re-wired a 12 volt battery -with a variable voltage connecting mount- to work with my old Arri and didn't have an issues. The new camera seems to have an issue on shots longer than 30 seconds. The frame rate starts to drop by about 1-5 frames per second as if the camera is struggling. I guess my questions are, 1. is this a motor, camera or battery connectivity issue? Is it something with the take up reel? Have any of you come across similar issues with the Arri-s? Is it fixable? 

 

Thanks in advance.

 

-c

[Satsuki Murashige]

Sounds like not enough power for the motor. Is the motor 12v or 16v? And do you have a way of checking how much voltage is actually coming out of the battery? 

[Carl Elsaesser]

The motor is either 8V (the fixed 24 fps motor) the others are two different kinds of variable speed motors that take 12V. At least that's that I assumed to the best of my ability; could the variable speed motors actually be 14v? 

 

And I don't have a way of checking the battery voltage other than what the output nob says on the v-mount- one for 8v and one for 12v. Can I ask a basic question... how would I do that, check the actual voltage from the battery? 

Thanks! 

 

C

[Satsuki Murashige]

2 hours ago, Carl Elsaesser said:

1. could the variable speed motors actually be 14v? 

2. how would I do that, check the actual voltage from the battery?

1. No idea, but I’m sure Dom Jaeger would know.

2. Use a voltmeter or multimeter. https://www.protoolreviews.com/how-to-use-a-voltmeter-multimeter/

[Robert Hart]

There may be a tight take-up clutch bogging the motor down as the roll gains diameter and more leverage against the motor and the outgoing roll loses diameter and is harder for the motor to drag film from. I don't know what system your camera has but there may be some form of friction clutch with an adjustable compression spring. In the CP16, the take-up drive had to be set just right or the film would wind loose or if too tight, the cogbelt might become damaged if it was deteriorating. 

[Brendan Collins]

Carl, the variable speed motors work at 8V. I would say that you are losing voltage inside, it happens to my Arri 16 M . (If I put 8v in, only 5v shows at the motor.) Or maybe even a bad ground connection to the motor?  I would suggest sending it in for servicing, as you don't want to pump too much power through it and then damage the electronics and everything. Or maybe something on the inside is super dirty/old grease that needs to be cleaned and re-lubricated? 

[Carl Elsaesser]

Next dumb question, suggestions on where to send in the camera to get a look over and clean up? 

(thanks for all the suggestions so far everyone!) 

 

c