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Thomas Dyrholm

Crystal sync motor for Arriflex 16S

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Hi

Recently I bought an Arriflex 16S/B G/S in very beautiful condition (will probably make another post about it in the near future). It came in the original box with Schneider primes, Angieneux zoom and all the good stuff. It also came with the original constant speed motor and the variable speed motor. I'm now searching for a crystal sync motor preferably the the Tobin TXM-22A. From what I've read it seems like these are now discontinued? Therefore I would like to hear if there are someone here who want's to sell theirs?

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They seem to pop up on ebay every now and then. There seems to be a jensen motor on ebay at the moment but no tobin ones. You can try the forum and also ask the Motion Picture Technology group on facebook, there is surely someone who has spare ones.

Btw if you want to convert the constant speed or the varispeed motor to crystal sync sometime later I could be interested investigating the possibilities for that. I am sure that there is others who already have working solution for that but I am building a external box system which should be adaptable to the task

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1 hour ago, aapo lettinen said:

They seem to pop up on ebay every now and then. There seems to be a jensen motor on ebay at the moment but no tobin ones. You can try the forum and also ask the Motion Picture Technology group on facebook, there is surely someone who has spare ones.

Btw if you want to convert the constant speed or the varispeed motor to crystal sync sometime later I could be interested investigating the possibilities for that. I am sure that there is others who already have working solution for that but I am building a external box system which should be adaptable to the task

I did notice the Jensen motor but I'm a bit hesitant to place a bid on it since it's probably very old and since it's so difficult to find any information about it. If someone here knows anything about it please tell us everything you know 🙂

Right now I'm trying to find the simplest and most reliable solution for crystal sync but maybe I will look into the possibility of converting the existing motors to crystal sync in the future if it turns out to be too expensive.

 

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12 minutes ago, Thomas Dyrholm said:

Right now I'm trying to find the simplest and most reliable solution for crystal sync but maybe I will look into the possibility of converting the existing motors to crystal sync in the future if it turns out to be too expensive.

I think it would probably be easiest for me to convert the variable speed motor using a external control box with the crystal sync electronics inside and possible to arrange different battery options if needed. I was thinking something like a 6-speed small and compact version without display or a larger one which has a display and from 12 to 16 speed presets. Could be an interesting project when I get my Konvas 15EPSS crystal control finished :)    

making these is pretty time consuming and costs a bit but it is fully possible. I think there is others converting these motors too (not sure) but you can always PM me later if you are interested in modifying the varispeed motor and I can look at it when having time :)

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Posted (edited)

Hi Thomas, 

I have exactly the same model (16S/B-GS) and been fashioning new power supplies for it the past couple of weeks.

As regards motors, Arri themselves produced the Variable Speed Motor (probably the most common one still in use), running of 8.4 V battery power for 4-48 fps, and then two types of constant speed motors, known as Governor Controlled Motors, one for 24 fps, one for 25 fps. They also take 8.4 V, although technically, you could power them with 6V car batteries at the time too, for around 18 fps. 

For the B-GS models in particular, Arri later produced a new model of Governor Controlled Motor, with a transistor (339 301) which ran at pretty reliable 24 fps, allowing for sound sync work. 

At a later point, Arri produced their own crystal synch motor, mains powered. These require the 42 V transformer to output a particular type of motor. There's one or two on eBay right now, and I'm fixing up an old one (which seems intent on running on a rather unusual 26 fps). See one at https://www.ebay.co.uk/itm/ACCESSOIRES-pour-CAMERA-ARRIFLEX-16-mm-Moteur-Synchrone-42V-Bte-dalimentation8V/200768423141

Tobin were third party suppliers and they're no longer around, although the motors still pop up every now and then on eBay and equivalent sites. They produced both variable (TM models) and constant speed motors, as well as crystal synch (TXM models). Jensen were another supplier, but a bit less common than Tobin, and harder to find these days. 

The main thing to look out for is your power supply. Unless I'm wildly mistaken, the Jensen motors take 12 V, and if you're running the 400 ft mags with a torque motor not fitted for 12 V, you're at risk of ruining that torque motor.

Edited by Teunkie Van Der Sluijs

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On 8/7/2020 at 6:35 PM, Teunkie Van Der Sluijs said:

Hi Thomas, 

I have exactly the same model (16S/B-GS) and been fashioning new power supplies for it the past couple of weeks.

As regards motors, Arri themselves produced the Variable Speed Motor (probably the most common one still in use), running of 8.4 V battery power for 4-48 fps, and then two types of constant speed motors, known as Governor Controlled Motors, one for 24 fps, one for 25 fps. They also take 8.4 V, although technically, you could power them with 6V car batteries at the time too, for around 18 fps. 

For the B-GS models in particular, Arri later produced a new model of Governor Controlled Motor, with a transistor (339 301) which ran at pretty reliable 24 fps, allowing for sound sync work. 

At a later point, Arri produced their own crystal synch motor, mains powered. These require the 42 V transformer to output a particular type of motor. There's one or two on eBay right now, and I'm fixing up an old one (which seems intent on running on a rather unusual 26 fps). See one at https://www.ebay.co.uk/itm/ACCESSOIRES-pour-CAMERA-ARRIFLEX-16-mm-Moteur-Synchrone-42V-Bte-dalimentation8V/200768423141

Tobin were third party suppliers and they're no longer around, although the motors still pop up every now and then on eBay and equivalent sites. They produced both variable (TM models) and constant speed motors, as well as crystal synch (TXM models). Jensen were another supplier, but a bit less common than Tobin, and harder to find these days. 

The main thing to look out for is your power supply. Unless I'm wildly mistaken, the Jensen motors take 12 V, and if you're running the 400 ft mags with a torque motor not fitted for 12 V, you're at risk of ruining that torque motor.

Actually I think the constant speed motor that came with the camera could be the new model you're talking about. Is there a way to determine wether it's the new or the old one? Mine has a small box on the side - could that be the transistor your'e talking about? I'm pretty sure that the camera itself is on of the last that left the factory - it's from the beginning of 1975 according to Arri. It has a built in light meter which seems to be pretty rare?

Regarding power supplies I've been looking into different solutions. I found a pretty standard Tilta V-mount plate that has a 8V output. To me it seems to be the easiest and hopefully most reliable solution. Probably not the cheapest though. Also I believe the original motors were built for 8V and not 8.4V. I could be wrong but remember I read it somewhere in one of the original manuals for the camera. For the light meter I guess it's quite important that the voltage correct? 

 

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Posted (edited)

Ooooh, that is very interesting. I have not come across the models with inbuilt light meters, nor constant speed motors with that little box on the side. That might well be the transistor? A person likely to be able to tell you will be Sean Charlesworth, who was head repair at NYU looking after their sizeable 16S collection.

I'm afraid I cannot advise you on the power supply with a view to the light meter. But I think you're absolutely right to err on the side of caution; light meters are sensitive bits of equipment. 

Both the variable speed motors and the governor controlled constant speed motors were kind of reliable in their frame rate. But the most reliability requires a crystal sync motor - although that transistor model was apparently pretty good - good enough for the B-GS to run sync sound, in any case. 

As regards power supplies, the camera itself can take a bit of range: 6V for 18fps, 8V for standard 24 or 25 fps, and up to 12V for 48 fps. Do not use 12V with the 400ft magazine unless you have the magazine torque motor altered to take this. Also, it's not advisable to run the camera at 12V for long amounts of time and without film; it can really damage your motors. 

I'm sure you'll have come across the options people use most frequently. A common DIY solution is a rechargeable RC battery, which tends to come in 8.4 V. They're fairly inexpensive. See this topic for more info. 

That's the set-up I'm using at the moment. I have a couple of issues with it, though. One is that these kinds of batteries don't hold charge for very long, and likely only last a few years. They sure hold enough charge to run the camera for a decent amount of time, but if you're needing to replace them every few years, isn't it better to find a more durable solution? Also, my RC battery fluctuates, from 7.8 to 9.4 V. Might be age, but it's not great. I could technically install a voltage regulator to at least step down a higher voltage to an exact 8V, however, that doesn't allow to boost up, plus most voltage regulators require a minimum difference of 1.5 V between input and output to be effective. 

Michael Leake has a homebuilt battery pack, which he explains in this forum post here. It looks like he uses a buck convertor voltage regulator, judging by the photos. 

I think if you have V-Mount batteries lying around for other purposes anyway, that's a really solid way into powering the camera, but it's not a solution I've come across a lot in this forum, for whatever reason. Alvin Morris demonstrates a version of it in this video here. He's using a Tilta plate. There are a few other manufacturers who offer 8 or 8.4V outputs on their V-plates, but the Tilta is definitely the better rated one. 

Theoretically, you could get a basic, cheap V-mount plate that doesn't output 8V, and install a voltage regulator between battery and camera to get the exact output you want, but I don't what you'd need to take into account with a view to the camera's impedance. I imagine the boards at Stack Exchange might provide some wisdom...? 

Let me know how you get on. Has yours been converted to take XLR input, or are you one of the lucky few to still have the original ARRI plug on the back? 

 

Edited by Teunkie Van Der Sluijs

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Hi Thomas and Teunkie

Thomas--I was just wondering how you got along with your power supply?  I recently (like 2 days ago) acquired a big

lot of 16mm gear including an Arri S and and Arri S/B (both working), a Tobin sync motor, the Tobin miliframe motor, the Arri variable motor, and the Arri fixed speed motor, two 400 foot magazines, torque motor.. (and a broken Beaulieu R16 and loads of glass).  Anyway was curious what you came up with for power.  I do like the idea of using V-mount batteries.  I have a few of those already and I need to test the Arri motors.  Both cameras worked with the Tobin motor--I was able to test that with a 12 volt 4-pin power supply that I borrowed from my LRH but i had no way of getting power to the 8v motors.  If I got that plate I would just need someone to build me a pair of cables--one to a 4 pin for the Tobin and one to the original Arri plug.  I have two of the AC cables so I don't have to hunt for the connectors. Anyway would love to hear about your experience building a power supply.

Tuenkie--how can I tell if the torque motor has been modified to 12v?

c

 

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