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Need help on powering my Arri 16BL


Keegen Moore

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So I've recently acquired an Arri 16BL for an upcoming short film I'm directing but am really not that knowledgeable or experienced in this format so I was hoping to get some help. I've been doing some research on how I'm gonna power this thing but there doesn't seem to be a lot of resources for this camera. I was planning on using a v mount battery and connecting it that way but have run into a problem. I've looked thru the original manual but am slightly concerned because the back of my Arri (where the battery port is supposed to be) is missing. I'm assuming the previous owner changed some things on it but again because I'm very new to this I'm at a standstill as to what to do. 

If anyone has any suggestions on how I should power this that would be greatly appreciated!

Thanks 

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  • 2 weeks later...

Wow, this takes me back 30 years.

The first movie camera I owned was a BL16.

I slid sideways into film from a previous career as an electrical engineer, so the first thing I did with my new-to-me camera was to disassemble it and reverse-engineer it in order to build a crystal sync box. Ah.. the good old days. Try doing *that* with an Alexa.

Anyhow..

The cavity in the back of your camera is supposed to hold a circuit board for speed regulation. Most of these cameras shipped with an analog speed controller that wasn't really crystal sync, but kept them reasonably near a constant speed.

The motor shaft included a tiny alternator that would generate a “pilot tone” near 4800 Hz, and that tone would be sent to the audio guy who recorded it on a separate audio track. That tone was mechanically tied to the frame rate so as the camera wandered, so did the tone, and the audio rate could be resolved back to the film rate in post.

There were true speed accurate controllers available ( the crystal sync everybody talks about, named when crystal timekeeping was still a new thing ) which compared this pilot tone to a crystal oscillator to keep a precise 24 FPS. They were external devices which plugged into a 10 pin Amphenol connector on the regulator circuit, which you are missing, or later, when electronics got small, replaced the regulator entirely ( Clive Tobin used to make one like this ).

Either way, these circuits interfaced with the innards of the camera through that blue multipin connector, which, I'm assuming is... well... now disconnected.

Don't know what the red and black wires are about. Maybe someone took the express route to power the motor. Also, where does the blue wire go? And what's with that cable clamp? That is not original equipment.

First, I think you'll have to determine how much has been shuffled around inside the camera.

The motor is under the cylindrical cover on the right of the camera. Take out the 4 screws and pull it off so we can get a look inside.

Specifically, we're looking to see how the power to the motor has been modified. It used to be driven PWM-style by a large power transistor mounted to the frame (looks like a flat silver disk the size of a quarter). Also, we want to know if the pilot tone generator is still intact (that's still required because we need a feedback signal)

Post pictures.

Also, while we're at it, open the camera door. Right in the middle of the camera you should see a clear plastic plate with a couple of gears visible under it. The gears should be stamped either 24 or 25, indicating where the regulated speed was initially set up for either film or European TV speed.

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Hi Keegan;

 

I had a day to think about it some more, and to look up some things, and I realize that I got some things kinda mixed up in my first post,  (I've seen the insides of a lot of cameras and they all start to blend together).

I think I have a better answer for you, and it actually looks better for you than I thought it did yesterday.

The cavity in the back of the camera used to house a circuit board that was used to mark the film and generate a sound tone used for post production sync. The open hole is disconcerting, but the camera can run without it.

The circuit that does the speed regulation is inside the camera, built up around the motor assembly, and if my memory is working right today, I don't think it's all that complicated. The base model motor (probably what you have) had a mostly mechanical governor similar to the one found in the motor for the ST, there were just a few electronic components controlling a big power transistor, which in turn supplies a regulated current the motor.

The signals in this drive circuit were accessible to the outside world through a 9 pin circular connector, located on the right side of the camera, in the bottom rear corner (not the one up above the motor, that one is for sound).

This 9 pin plug provided power and allowed for connection to the pilot tone generator and, importantly, to the motor drive transistor.

Power used to connect here. Commercial crystal sync units also connected here, where they would use the pilot tone feedback and take over driving the big power transistor, to control camera speed precisely.

Bafflingly, you do not have this connector anymore. I can't tell from the photos if it has been removed or maybe you had a weird custom camera where something else was installed.

Either way, somebody has clearly modified things since this camera rolled off the line in the late 60's because that is not the type of wire Arri used back then. Heck maybe you really lucked out and got a camera that had an upgrade motor installed (that would be pretty sweet, actually), and for some reason whoever did the job decided to take the power out the back for some reason .

I suspect that you'll have to investigate further by removing the motor cover and looking inside. It comes off easily with 4 screws. Pop it off and send us a photo or two of what's in there.

 

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Thank you, I really appreciate your help! Im still in the process of acquiring the right screw driver to gain access to the motor but Ill post pics as soon as I can. In the mean time here's a pic of the inside of the camera. I'm very new to this but I'm trying to get it to work with a D tap battery.

Thanks

https://ibb.co/RhTCwdN
https://ibb.co/9TvxWLN

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Ohh...Kay...

Whelp, this is a weird one.

It looks like you have the 120v synchronous AC motor.

Again, I'm working from memory, but I seem to recall that this camera came with either the 12v governor motor or, as an option, a AC line voltage motor, and it looks like you have one of the later. That's not totally weird, since an AC motor was a fairly common option for both 16 and 35 mm cameras that were used in a studio setting in the 60's and 70's, since they gave better speed regulation and removed the need for batteries in an era when batteries kinda sucked.  

That being said, someone has clearly modified things after the fact, since that is definitely not OEM Arri wiring.

I have no idea how the power is hooked up. My BL and every other one I've seen had a 9 pin connector mounted just aft of the motor housing. It's hard to tell from the photos whether your camera had this removed and the hole plugged, or whether there was never one there in the first place (although that right-angle piece on the rear plate looks suspiciously like the part that was used to mount the connector). Somebody has apparently bypassed all this, maybe to install a preferred connector

I am  pretty much at a loss here. I am unfamiliar with the 120V motor, but if it works, then maybe you can find someone to clean up the wiring and you can operate it off line voltage.

You probably don't want to go experimenting with this motor until you get a more solid ID on it. You especially don't want to try putting DC voltage on it unless you know what specific kind of motor it is.  Many types of AC motors don't have enough coil resistance to properly limit the current that flows through them. These motors instead rely on the inductance of the windings interacting with the line frequency to limit current to a safe level, and this scheme doesn't work with DC.

Conversely, some motors are fine with either flavor, and are just as happy to run on AC as 120v DC. I have no idea which kind Arri used, but to me "synchronous" implies frequency dependent because universal motors tend to have a lot of phase slip.

 

Also, just for reference, the preferred way to remove and reattach the motor in this camera is to remove the spur gear first. I don't know if it's just an urban myth, but Arri advised that the gear was less likely to be damaged that way. I honestly don't remember how I did it with my camera.

To remove the gear you take out the screw in the shaft. Obviously, this means that you have to pull off the little plexiglass gear window. Be very Very, VERY careful when you put the window screws back in, it's really easy to crack the little mounting ears with excessive screw pressure. I cracked one of mine that way.

 

 

 

 

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