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D-tap to 12v XLR for SR2


Alex Levin

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I recently purchased an SR2 and, while it came with a battery belt, I'm curious to do a little research to see if I can power it via AB or v-mount bricks. Does anyone here with more knowledge than me think this would be a workable solution? It seems to step down whatever is coming from the battery to 12v, which should run the camera. I guess Im not sure of the amperage and would prefer not to fry my camera.

 

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I can't help with the details, but a motor only cares about voltage. The capacity in amp-hours merely determines how long a charge will last. Too low a rating may tax the batteries, but it won't hurt the camera. There's no such thing as too many amp-hours.

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I can't help with the details, but a motor only cares about voltage. The capacity in amp-hours merely determines how long a charge will last. Too low a rating may tax the batteries, but it won't hurt the camera. There's no such thing as too many amp-hours.

 

Thanks Mark. Totally makes sense. I have a feeling I'm going to be delving into some more analog elements of this camera. I'm so used to digital and not having to worry about these kinds of things and everything just playing nice together.

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You absolutely can, I haven't done it in a long while but I used to power it off the unregulated "12v" output on my steadicam all the time. The cams were all serviced and modern so the internal voltage regulators were plenty good to deal with slightly (1.5v) more voltage than normal. But because SR2 batteries are actually 14.4v - and modern bricks are technically 14.4v too, you're in luck and it should work. Just know that unregulated lithium bricks can be over 17v hot off charge, so I believe its prudent to not put that much out immediately unless you know the specs of the voltage regulator in your personal camera (SR2's were all over the place in what electronics were inside from service). But like all film cams, the initial roll-up of the motor is the largest current demand so as long as your battery can keep up with that initial spike, it'll power just fine. Most modern lithiums can handle well over 15A bursts/10A continuous which is plenty for much bigger cams than the little SR2.

 

The old trick was - if you know your batteries are always going to come off charge at 17v then add two diodes to drop the voltage to 15.5v which was safe. I can't recall exactly what diodes/wiring but it's really easy to google.

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I asked an electronics tech years ago what was the maximum input voltage an SR2 could handle and he thought it was around 18V. So you should be OK with nominally 14.4V sources that top out at a little under 17V fully charged, but it is skating close to the limit.

 

The original on-board batteries were 12V NiCads, which only get to around 13.5V fully charged.

 

A D tap should be able to handle the current draw of an SR2, which from memory is around 1A just for the camera, maybe spiking to 2 or 3 Amps with a full mag on start-up. So less than 50W, unless you have a whole stack of accessories being powered out of the camera as well, or you're shooting high speed.

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