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GPI Sled Power Failure


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#1 Daniel Loher

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Posted 11 May 2011 - 06:02 PM

I recently came back from a one day commercial shoot where I ran into some nasty problems.

I arrived at the set, set up my GPI PRO Rig, put the Moviecam LT on and ran my quick test that everything works.
We were shooting at 25 fps. My AB Hytron 50 batteries were fresh and fully charged, the 12/24V switch set to 24V and everything set up correctly but the camera would not speed up to 25 fps.
Also the jumper block was the correct one (feeding the Monitor separately from CAM/ACC)
At the same time the monitor kept going on and off in a similar pattern as the camera jumping from 24- 24.7 fps.
We found a cheap solution that pretty much defeats the purpose of using a steadicam but it made the job work for the situation, thank god.

Has any one had any similar experience. Hytron Batteries not feeding sufficient power? / Too thin cabling in the GPI post?
I really don't want to run into this problem again, especially now that cameras are getting more and more power hungry.

Thanks for any advice.

Edited by Daniel Loher, 11 May 2011 - 06:03 PM.

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#2 William Demeritt

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Posted 11 May 2011 - 08:27 PM

Did your quick test include running the camera at 25fps? Did it work at 25fps during the test but then fail on set?

What was your other testing methods trying to get it running?
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#3 Brian Freesh

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Posted 11 May 2011 - 10:12 PM

Will, I think it did not work during the test, but I may be misreading.

Did you have a Moviecam SL or an Arricam LT? (or an Arri upgraded SL, forget what they are calling those, SL Advanced?)

This reminds me almost exactly of my current issues with my Ultra. The answer for my rig is that there is a power drop along the sled somewhere. It also affects my monitor even when powered separately. the theory behind that had something to do with the camera trying to pull extra power through the video line. I dunno electronics myself, so I can't explain that one. I have the trouble with high-amp draw cameras. So 12v HD and older 12v film cameras (Arri 3). I haven't had the problem with a 24v camera except to supply 24v to a Panavised Arri 3 which split the 24 into dual 12 inside the camera for the camera and speed base.

The way to test it would be to use a meter to test the batteries fresh off the charger and then to test what is coming out of the DB. There will be a drop, but it shouldn't be too much (I dunno what is acceptable, on my rig it is a volt, but I have a longer run)
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#4 Jens Piotrowski SOC

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Posted 12 May 2011 - 12:19 AM

"I arrived at the set, set up my GPI PRO Rig, put the Moviecam LT"

sounds out of character for the PRO sled, what camera was it Compact or SL, there is no Moviecam LT.

also some older older Moviecams don't like more 24 Volts, two freshly charged Hytrons in line are between 28 and 31 Volts....
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#5 Joseph Arena SOC

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Posted 14 May 2011 - 08:44 PM

I recently came back from a one day commercial shoot where I ran into some nasty problems.

I arrived at the set, set up my GPI PRO Rig, put the Moviecam LT on and ran my quick test that everything works.
We were shooting at 25 fps. My AB Hytron 50 batteries were fresh and fully charged, the 12/24V switch set to 24V and everything set up correctly but the camera would not speed up to 25 fps.
Also the jumper block was the correct one (feeding the Monitor separately from CAM/ACC)
At the same time the monitor kept going on and off in a similar pattern as the camera jumping from 24- 24.7 fps.
We found a cheap solution that pretty much defeats the purpose of using a steadicam but it made the job work for the situation, thank god.

Has any one had any similar experience. Hytron Batteries not feeding sufficient power? / Too thin cabling in the GPI post?
I really don't want to run into this problem again, especially now that cameras are getting more and more power hungry.

Thanks for any advice.

Daniel ,
If you are using a Moviecam Compact or SL old generation you may need to use a voltage regulator box (it would help you feed the camera with the same constant amount of voltage) , I had one made long time ago and always worked fine .
As Jens already mentioned this camera voltage tolerance is not great , the new generation Mark 2, I never had problem with.
Cheers
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#6 Matt Petrosky

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Posted 24 May 2011 - 12:40 AM

Daniel ,
If you are using a Moviecam Compact or SL old generation you may need to use a voltage regulator box (it would help you feed the camera with the same constant amount of voltage) , I had one made long time ago and always worked fine .
As Jens already mentioned this camera voltage tolerance is not great , the new generation Mark 2, I never had problem with.
Cheers


Agreed Jens and Joseph are correct, problem is most likely that the the old Moviecam cameras will not run properly on anything much OVER 24 volts. Your steadicam with fresh A/B Hytron batts jumped to "24" volts is actually passing around 28-30 volts to the camera, maybe more. While this is great for a 435 or Arricam, is overloads the Moviecam and causes the motors to run erratically. Otto and Clairmont used to have voltage regulator boxes/cables that keep the voltage capped at 24v as even modern block batteries tend to put out well over 24 volts as this was a common problem.
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