Help needed: What to do with blocked/jammed Arri Magazine?

[Janis Lionel Huber]

Hello 

We seem to have our first jammed/blocked Arri 16mm SR HS magazine. The empty magazine is running well. It happened during shooting and suddenly turned off with a noise. It already happened on the same roll two weeks ago, but I didn't think much of it and it ran again. Now it doesn't turn on anymore and also doesn't andvance when pressing "Test". I hope I didn't already break something. The gear on the receiving end feels blocked. 

What to do best? Cut the film and save what's already shot? Try to open and 'feel' the problem? Are jammed magazines usually simple errors or often need professional servicing?

Thanks for the tips from experience! Much appreciated! 

[Dom Jaeger]

Can you clarify what you’re saying? 

The mag jammed, and the camera wouldn’t run or even inch with the phase button. But the camera runs fine with the jammed mag removed and an empty one fitted?

And when you tried to manually inch the jammed mag (after releasing the loop from the pressure plate) the drive gear felt stiff to turn?

 Then you need to investigate. In a change bag or dark room I would cut the film in each chamber and remove the two rolls, exposed and unexposed. Then investigate the jam in the light. 

Check if there is any damage to the drive gear teeth, check if the film is damaged, if one of the sprockets became misaligned from the perfs, if the take-up tension is ok (the take-up slips with slight force), if the feed spindle turns smoothly with slight resistance. You can remove the mag throat assembly by undoing  two screws to check for film pieces stuck in the path. Possibly best to let a tech check it if you’re not very experienced and the fault is not obvious.

A jam could be caused by a faulty mag or just if you loaded poorly (wrong loop size) or fitted the mag to the camera with the loop too far off centre. Damaged drive gear teeth combined with a stiff take-up is a common cause if it happens towards the end of the roll. Less likely but still possible, is a camera fault.

Edited March 1 by Dom Jaeger

[Janis Lionel Huber]

45 minutes ago, Dom Jaeger said:

Can you clarify what you’re saying? 

The mag jammed, and the camera wouldn’t run or even inch with the phase button. But the camera runs fine with the jammed mag removed and an empty one fitted?

Yes. With "Phase" button you mean the "Test" Button? And yes, the camera seems to run fine with the jammed removed and an empty one fitted, exactly. 

 

Quote

And when you tried to manually inch the jammed mag (after releasing the loop from the pressure plate) the drive gear felt stiff to turn?

Yes! 

Quote

 

Check if there is any damage to the drive gear teeth...

Ok. I will try my best (before it goes to the tech which was planned anyways back home). Should I cut the film and already save the shot part or can I do this with the film still loaded? I will only be able to check the gear teeth once I do something because it's that stiff and I can't turn it 360°

And yes, the film is running low (on 70ft) 

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A jam could be caused by a faulty ...

The gear teeth of the camera are not damaged. When I press the 'test button' the camera (with the empty, fine magazine) is rather loud, but when running on 24fps sounding normal (hear sound files attached, cam was on wood, so there is some resonance - attached to this post or downloadable here https://www.swisstransfer.com/d/58f21512-3fbd-495d-a015-351c4b080085)

Thank you!! 

 

 

 

 

Edited February 28 by Janis Lionel Huber

[Janis Lionel Huber]

..and how can the mag be mounted "with the loop too far off center"? Because the pins hold it in place. 

Update: I opened the takeup side. The film was not taken up correctly and created a mess before the spool (which already has quite some film on it). How do I best deal with this? Cut it and try to roll it up properly?

[Janis Lionel Huber]

After the 'Operation' 🫥 Was pretty messy on the take up side.

[Tyler Purcell]

5 hours ago, Janis Lionel Huber said:

The film was not taken up correctly and created a mess before the spool (which already has quite some film on it). How do I best deal with this? Cut it and try to roll it up properly?

Yea, this is pretty typical when the coreless core holder doesn't lock the film in place. The coreless adaptor is very good, but you have to make sure it runs smoothly. Sometimes they get bent/warped and rub the inside of the cover if it's misaligned. So an older out of adjustment clutch assembly on the take up can simply cause it to jam/stop spinning freely. Also, the lever that holds the film in place on the coreless system, can also be not free. So I would check that as well, make sure everything works nicely with some fresh test film. 

If you want to cut and proceed shooting, that's another way to roll of course. 

Also, if it's an HS mag it should have a plastic drive wheel. Make sure it does and not a yellow gummy gear, which are prone to failures and can cause weird jamming issues as well. 

[Dom Jaeger]

12 hours ago, Janis Lionel Huber said:

..and how can the mag be mounted "with the loop too far off center"? Because the pins hold it in place. 

The loop latches under the pins to align it with the pressure plate but before fitting the mag to the camera you need to make sure the loop is centered top to bottom within the mag throat. 

But this looks like a take-up problem rather than a bad loop, so check the take-up is turning ok and the slipping tension is not too weak. See if you can identify what stopped the take-up turning. Maybe the film was not attached properly to the core or the collapsible core, or something was rubbing on the door. 

[Janis Lionel Huber]

Thank you Tom and Tyler for your forever great help! Young people like me can be happy to receive this knowledge. 

12 hours ago, Tyler Purcell said:

Yea, this is pretty typical when the coreless core holder doesn't lock the film in place. The coreless adaptor is very good, but you have to make sure it runs smoothly. Sometimes they get bent/warped and rub the inside of the cover if it's misaligned. So an older out of adjustment clutch assembly on the take up can simply cause it to jam/stop spinning freely. Also, the lever that holds the film in place on the coreless system, can also be not free. So I would check that as well, make sure everything works nicely with some fresh test film.

Would you recommend the Bobby over the collapsible core? Cause we have one magazine with collapsible core and one with bobby. For workflow purposes I want to change this to one system. 

5 hours ago, Dom Jaeger said:

The loop latches under the pins to align it with the pressure plate but before fitting the mag to the camera you need to make sure the loop is centered top to bottom within the mag throat. 

I did this. Do I also have to align the pressure plate a certain way? Because it is movable and can be moved a few millimeters.

12 hours ago, Tyler Purcell said:

Yea, this is pretty typical when the coreless core holder doesn't lock the film in place. The coreless adaptor is very good, but you have to make sure it runs smoothly. Sometimes they get bent/warped and rub the inside of the cover if it's misaligned. So an older out of adjustment clutch assembly on the take up can simply cause it to jam/stop spinning freely. Also, the lever that holds the film in place on the coreless system, can also be not free. So I would check that as well, make sure everything works nicely with some fresh test film. 

If you want to cut and proceed shooting, that's another way to roll of course. 

Also, if it's an HS mag it should have a plastic drive wheel. Make sure it does and not a yellow gummy gear, which are prone to failures and can cause weird jamming issues as well. 

Do the non HS mags have other wheels? I checked, it has a plastic wheel that seems in tact

 

5 hours ago, Dom Jaeger said:

The loop latches under the pins to align it with the pressure plate but before fitting the mag to the camera you need to make sure the loop is centered top to bottom within the mag throat. 

But this looks like a take-up problem rather than a bad loop, so check the take-up is turning ok and the slipping tension is not too weak. See if you can identify what stopped the take-up turning. Maybe the film was not attached properly to the core or the collapsible core, or something was rubbing on the door. 

What exactly do you mean with "slipping tension" this is on the takeup side? 

[Tyler Purcell]

1 hour ago, Janis Lionel Huber said:

Would you recommend the Bobby over the collapsible core? Cause we have one magazine with collapsible core and one with bobby. For workflow purposes I want to change this to one system. 

Collapsable works great, tho today labs prefer a core over collapsable. So if you want to make sure the lab won't ever have issues, use a core. 

1 hour ago, Janis Lionel Huber said:

I did this. Do I also have to align the pressure plate a certain way? Because it is movable and can be moved a few millimeters.

No the pressure plate doesn't need to be touched. As long as the film loop length is correct (measured to the little line under the mag) and you slot the film into the 4 holders on the pressure plate, you should be fine. 

1 hour ago, Janis Lionel Huber said:

Do the non HS mags have other wheels? I checked, it has a plastic wheel that seems in tact

HS cameras run louder, so Arri didn't mind using plastic on plastic drive gears for the magazines. Non-HS magazines run quieter, they use a yellow gummy gear to help reduce noise, but they fail over time. If the teeth are all in tact, then don't sweat it. But if you see chunks of teeth missing, that can easily cause the magazine to lose a loop and jam. I have rarely seen gummy gears in good shape, so we make a replacement for them. However, the plastic gears on the HS mags, should be good for life. Never seen one damaged/broken. 

As a side note, if your camera isn't an HS camera, you may want to invest in standard mags. The HS mags are not quite as accurate with the pressure plate, the film has a bit more float. The normal mags have a bit less film float and tighter tolerances and create a better image at 24fps, they're also quieter. 

1 hour ago, Janis Lionel Huber said:

What exactly do you mean with "slipping tension" this is on the takeup side? 

There is a clutch assembly in the spindle that the belt drives inside the magazine. Those clutches when worn can have too little tension. So if let's say the collapsable core is bent, it may strike the top of the door and simply not spin if the clutch is too loose. Where I don't necessarily think this is your problem, it can be something to think about if this issue happens more than once. One of the first things I do when I get SR mags in for CLA is feel how tight that clutch is and generally they're fine, but every once in awhile you see one that's way off. You can run the magazine with the door open with test film and see if it takes up ok. 

[Dom Jaeger]

On 3/2/2026 at 4:48 AM, Janis Lionel Huber said:

Do I also have to align the pressure plate a certain way? Because it is movable and can be moved a few millimeters.

No, just centre the loop in the mag throat and attach the mag. Then use the test (or phase on SR3s) button to engage the claw in the perfs before running, as per the manual.

On 3/2/2026 at 4:48 AM, Janis Lionel Huber said:

What exactly do you mean with "slipping tension" this is on the takeup side? 

The take-up spindle needs to slip as more film is wound on to the core or collapsible core (since the amount of film wound on with each revolution becomes greater as the diameter increases). So under the take-up spindle is a clutch that slips at a particular tension. A trained Arri tech will measure this tension with a special tool, and adjust the tension if it’s out of tolerance and ideally service the clutch if it hasn’t been done for a while. This is the tool:

 

 

[Janis Lionel Huber]

We finally took care of the problem magazine now and removed the shot film. When turning the sprockets/gear it really doesn't move smooth but goes staccato and when turning in the opposite direction it does a lot of clicks. There is still film stuck, @Dom Jaeger which two screws I have to open the throat assembly? Blue, green Orange? 

 

Edited March 18 by Janis Lionel Huber

[Janis Lionel Huber]

...or one of those?

[Tyler Purcell]

Start with those two, the assembly comes right out and then you can clean up the gunk inside, clearly there is some film stuck. 

this is mirrored on the other side, so the roller screw can come out if the rollers don't roll, but you should be ok. The orange labeled screws are not related to your issue. 

If you remove the pressure plate assembly and find the sprocket drive does not spin freely, it's kind of a pain in the butt to get that apart. You generally need to disassemble the whole magazine because the belt is held in there pretty tight and you don't want to damage it. So generally if the sprocket drive doesn't want to move for whatever reason, it's a whole CLA of the mag. 

Also, you need to make sure the pressure plate is out if you take the roller screws out because the roller will just fall into the cavity if you're not careful. 

 

 

 

[Dom Jaeger]

3 hours ago, Janis Lionel Huber said:

...or one of those?

Yes, you remove the two big screws top right and bottom left. Then carefully lift out the assembly. You can access the sprockets and rollers from there. Sounds like film stuck in a sprocket if it makes a clicking sound.

[Doyle Smith]

On 3/2/2026 at 11:48 PM, Dom Jaeger said:

No, just centre the loop in the mag throat and attach the mag. Then use the test (or phase on SR3s) button to engage the claw in the perfs before running, as per the manual.

The take-up spindle needs to slip as more film is wound on to the core or collapsible core (since the amount of film wound on with each revolution becomes greater as the diameter increases). So under the take-up spindle is a clutch that slips at a particular tension. A trained Arri tech will measure this tension with a special tool, and adjust the tension if it’s out of tolerance and ideally service the clutch if it hasn’t been done for a while. This is the tool:

 

 

I'm not as an experienced camera tech as Tyler, but insufficient mag takeup tension was my first thought. I was surprised to see my old familiar Arri takeup gauge still in use on an SR. Do you adjust it with the two tooth metal tool like on a IIC?

[Tyler Purcell]

3 hours ago, Doyle Smith said:

I'm not as an experienced camera tech as Tyler, but insufficient mag takeup tension was my first thought. I was surprised to see my old familiar Arri takeup gauge still in use on an SR. Do you adjust it with the two tooth metal tool like on a IIC?

You have to pull the entire clamshell apart and adjust on the bench. There an assembly inside the clutch part, which alters the tension via spring. So I set mine with it apart and then throw it together. Once you've done a few hundred of these, you know what it should feel like. It's rare for the tension to be off, but bent core less assembly? Gosh, happens all the time. I just got 6 mags in for refurbishment, 3 of them had bent core less assembles. The center shaft is round on the top and square on the bottom and that bottom part is very thin walled. So it's common for there to be some sort of added friction around the core less assembly, which causes the take-up to stop spinning. Obviously, the drive gear is another problem, but usually it's easy to identify a bad drive gear because it's right there when you load the thing. 

[Dom Jaeger]

4 hours ago, Doyle Smith said:

I'm not as an experienced camera tech as Tyler, but insufficient mag takeup tension was my first thought. I was surprised to see my old familiar Arri takeup gauge still in use on an SR. Do you adjust it with the two tooth metal tool like on a IIC?

There are experienced US-based Arriflex techs at Visual Products, Du-All and AM Camera.

The take-up clutch on SRs is adjusted from the compartment with a pin tool. You don't need to disassemble the mag to adjust it, in fact, that's the wrong way to do it, because the mag needs to be assembled to check the tension. The method is to measure the tension, adjust the clutch, measure again, and often make another adjustment or two to get it just right. The tension checking tool also shows you whether the clutch needs a service - if the tension jumps around or doesn't respond properly to adjustment then the clutch needs to be disassembled and serviced. 

If the tension is too low, it causes the film to wind on loosely, potentially coning and creating cinch marks when its tightened or flattened. Worst case scenario a bit of extra drag from a misaligned roller or something scraping and the take-up might stall completely.  If it's too tight or jumpy it puts excessive pressure on the sprockets and the drive gears, potentially damaging perfs or causing a jam. 

About half the mags I check need adjustment. They will still work if they're a bit out of tolerance, you just increase the risk of an issue. 

I very rarely come across issues with the collapsible cores, they're solidly made. But the platines (compartment floor plates) can become deformed as they are only thin aluminium. The rubberised paint surfaces can often get sticky, roller arms can get stiff, rollers need lubrication, the footage counter window cracks, soft rubber drive gears get damaged.