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

Janis Lionel Huber · February 28

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 · February 28

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 · February 28

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!

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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)

Quote

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 · February 28

..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 · March 1

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

Tyler Purcell · March 1

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 · March 1

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 · March 1

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 · March 1

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 · March 3

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: