Thread: Thanks for allowing me into the group! Question about Ptap with Komodo and SDI

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  1. #1 Thanks for allowing me into the group! Question about Ptap with Komodo and SDI 
    I'm a new Komodo owner/operator and noticed, on the Red Site, this warning about using P-tap cables and outboard accessories with the Komodo, especially where SDI is involved.
    I researched this site for any info but, didn't find anything specific to this issue.
    I own 2 Odysseys and an Atomos Shogun Inferno and want to use one of them as my outboard monitor.
    Red's warning, simply put is 'avoid using P-tap cables for powering accessories as they are not shielded'.
    After doing some research, it sounds like it's not just Komodo or other Red cameras and there are references to Arri cameras as well.
    I've been using P-tap cables for years on other cameras and never had a problem but, now I'm worried.
    Do you guys think this is anything to worry about? Or, is safe practice of powering everything down before connecting or disconnecting enough to mitigate the issue?
    I'd really hate to fry the SDI boards on this thing.
    Thanks again for inclusion to REDUSER!
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  2. #2  
    Senior Member Brian F Kobylarz's Avatar
    Join Date
    Dec 2007
    Norwich, CT. USA
    I always err on the side of caution.
    Indirectly related; Around 35 years ago, I produced and filmed an internal awareness video on ESD precautions for AT&T. For one segment, they provided me with a series of photos that documented damage to circuit boards after repeated hits by static electricity.
    It was very clear that you did not need a single event to cause a failure. It could be cumulative.

    The same could happen with any SDI board, Or with any piece of electronic gear for that matter.
    The better you are able to take care of your gear, the longer it is likely to last.
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  3. #3  
    Also wondering about this. I purchased the Osee G7 and not sure if I need to run a shielded power cable from the monitor to the Komodo. If so, does anyone have any suggestions on where to purchase this cable?
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  4. #4  
    As long as you follow the protocol for unshielded cables, you will be fine. Arri has a video that explains the situation a little better. But basically to avoid frying the SDI board in your Komodo, do not plug/unplug power cables on your rig with SDI cables connected. If, by chance, the positive pin makes connection before the negative pin while plugging in a power cable, the current will run through the system (and the SDI cables) wreaking havoc on anything that cannot handle that current.

    Ptap can easily create that situation as it is a big wonky connector that can easily connect the positive pin before the negative pin.
    Last edited by Dana Neibert; 03-21-2021 at 01:13 PM.
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  5. #5  
    Senior Member Christoffer Glans's Avatar
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    Jun 2007
    Stockholm, Sweden
    Aren't these cables flexible and protected?
    "Using any digital cinema camera today is like sending your 35mm rolls to a standard lab. -Using a Red is like owning a dark room."
    Red Weapon 6K #00600 Red Komodo #002397
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  6. #6  
    Senior Member Patrick Tresch's Avatar
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    Aug 2007
    Switzerland, Lausanne
    I use safetap to protect my evf
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  7. #7  
    Senior Member Aaron Lochert's Avatar
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    Oct 2013
    Tucson, AZ
    Quote Originally Posted by Patrick Tresch View Post
    I use safetap to protect my evf
    Obviously this is just one person's blog and can't verify this info myself, but I recall reading this article that claimed the SafeTap doesn't actually protect against this specific fault. It might protect your EVF but it can apparently still short through the SDI and fry the camera's board.

    The SafeTap Dilema

    It was brought to my attention via a client that there is a blog on Newsshooter that claims that the SafeTap and its protection features is a viable work-around for using P-Taps in a way that will mitigate the problem described in the Arri technical advisory. Finding this claim to be dubious, I actually put a SafeTap up on my bench to test this theory myself and found that the information in the article is not accurate. A SafeTap should not be relied upon to protect against this specific problem. In fact, it can actually worsen the issue. We do not recommend using SafeTaps for hot-plugging or when coaxial lines are already connected to your camera. In fact, we do not recommend connecting the output side of a SafeTap cable, turning on any devices, or plugging in any SDI lines until the SafeTap flashes green and connects the ground line.

    For additional context, upon testing, I found that the SafeTap disconnects the ground line instead of the positive line (like a transistor). This means that if you have a stray path to ground, (a BNC shield in this case) the positive voltage line will instantly connect, defeating the SafeTap's protection features entirely. Even if the cable shield is connected to the SafeTap’s negative output terminal, the positive line will always directly connect if there is another ground connection available.
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  8. #8  
    I bought ShieldRock available from the main suppliers
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  9. #9  
    Thanks. That's the way to do it
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  10. #10  
    Junior Member
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    Jan 2021
    do you have a link to that arri video?? Ive searched arrichannel and cant find it
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