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Downconverter issues

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#1 Brad Grimmett

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Posted 22 September 2011 - 09:57 PM

I'm on a show in NC at the moment and today was the first steadicam day. We have Alexas. When I built the rig I almost instantly noticed some breakup in the image in my monitor. It was strange and unlike any breakup I've ever seen before. It was strobing and then there was massive delay at one point, and most of the time it was at the bottom third of the frame. I have an AJA on this show and have never seen anything like this before. On top of the problems with my monitor, they were getting complete static, if anything, from my Modulus. We of course switched every single cable and couldn't get rid of the problem. My 1st and I are assuming it's the AJA, but it's hard to be sure. We've ordered another one but I'm hoping maybe someone has some experience with this specific issue.
The owner/operator who rented us the gear says there is something called PSF or SPF that is a setting in the camera that maybe needs to be changed. I don't have a clue what that is and neither do either of the 1st's. By the way, we're out in the middle of nowhere, so the chance that it's interference seems to be low. Any thoughts or suggestions? Thanks.
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#2 William Demeritt

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Posted 22 September 2011 - 10:23 PM

A few questions for the techies:

- What kind of sled do you have? Monitor?
- How is the AJA being powered? How is the monitor, camera, etc being powered?

I haven't had time to track down the problem, but I know when I run my Decimator 2 off the CAM PWR on my PRO2 sled, and use my Modulus 2000 with the 4-pin LEMO connector for power and video signal, I get video distortion on the receiver end. If I use the 2 pin AUX PWR port on my sled to power the Modulus 2000, I get no video distortion. Of course, it primarily happens with RED cameras, I haven't tested it yet with an Alexa.

Looking online real quickly, it looks like the AJA downconverters can handle PSF (Progressive segment frame, although I heard it once called Progressive shift frame) or regular P (progressive).
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#3 matthew pearce

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Posted 22 September 2011 - 11:03 PM

I also tried to set up an AJA with an Alexa the other day and it seemed to freak the camera out.
Guessing it had to do with trying to power the alexa 24v and power the AJA 12 volt ( The AJA i have has 5-18V, printed on it at power in plug)
Reading up now, sure I'm not the first to have the problem.?
I was trying to run the sled in 24v mode, power the AJA of the sled as well. (old pro 1)

thinking a 24 volt decimator may be best plan., and lighter.
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#4 Russell McElhatton

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Posted 23 September 2011 - 10:33 PM

There is a P/PSF setting for the monitor out in the Alexa menus. On my Decimator it is only a nuisance if it is set to PSF ( minor image pulsing) but using an AJA when we first ran the Alexa on my PRO/TB6 combo we had rhythmic cutting in and out to black screen similar to what you described. The monitor out must be set to P in the menu. Sorry I cannot be more specific about how to accomplish this as I do not make the change, Kieth does. If you do not change back when going to studio the assistant monitor will not work. As far as static type interference I experience that occasionaly but not to the extent that it interferes with operating (I cannot seem to establish a quid pro quo for this). Power for the Decimator/AJA comes from D tap and not from the sled. I no longer use my SD xmitter as we fly the Boxx but that was powered from PRO vid/power with no interference problems. It seems that since we no longer have a video tap but all is video the power source should not matter, we really should not need a separate battery for monitor/video tap/xmitter anymore at all. If you cannot find the P/PSF setting PM me and I will call my assistant for the procedure.
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#5 Brad Grimmett

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Posted 13 October 2011 - 05:05 AM

Thanks for the tips guys. It was the psf setting that was causing the problem. Very odd. Good to know for the future.
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