Thread: The SDI issues

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  1. #61  
    Senior Member Robert Hofmeyr's Avatar
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    On a thread in the Red Komodo Users FB group, this isolator was suggested to prevent this issue: https://www.bhphotovideo.com/c/produ...isolation.html. Can anyone here confirm that this will work?

    I can't find it locally though, but I did find some much cheaper CCTV isolators like this one: https://www.communica.co.za/products...p-isolator-iv2. Will this help?
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  2. #62  
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    Quote Originally Posted by Robert Hofmeyr View Post
    On a thread in the Red Komodo Users FB group, this isolator was suggested to prevent this issue: https://www.bhphotovideo.com/c/produ...isolation.html. Can anyone here confirm that this will work?

    I can't find it locally though, but I did find some much cheaper CCTV isolators like this one: https://www.communica.co.za/products...p-isolator-iv2. Will this help?
    All these devices kill the "12G" signal though. That's the issue.

    JB
    John Brawley ACS
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    www.johnbrawley.com
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  3. #63  
    Senior Member Robert Hofmeyr's Avatar
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    Quote Originally Posted by Alex Lubensky View Post
    If you watch the Arri video regarding the subject once again - they are talking about the connectors specifically, not the power source. It states:

    "Camera SDI outputs can get damaged when an accessory is connected to the SDI output and is powered through an unshielded cable. All cameras, including all ARRI cameras and other SDI devices, can be affected by this."

    D-Tap as a connector only has 2 pins, + and -. Same goes for the Sony NP-F style batteries, they only have + and -. I suppose if + connects first, and the camera has it's own power, it's the same as if you plug the d-tap power of the monitor with sdi connected after connecting the power source to the camera.
    I understood that video a bit differently. When the positive pin in a d-tap that is being used to power a monitor is connected before the negative, the SDI cable completes the circuit causing the board to blow. This requires the power source to be the same for the camera and the monitor. On the other hand, if one connects a dedicated battery to a monitor and the positive connector makes contact before the ground, it does not form a circuit. So, as far as I understand it (and I am no expert in this field), the ground loop problem requires the camera and monitor to be powered from the same source. I believe it may also be possible for two separate batteries powering the monitor and camera to have different floating ground voltages thus causing current to flow through the SDI cable, but this is a bit beyond my understanding.
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  4. #64  
    Senior Member Robert Hofmeyr's Avatar
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    Quote Originally Posted by John Brawley View Post
    All these devices kill the "12G" signal though. That's the issue.

    JB
    Thanks John. I don't need a 4K signal. Do you know if I would still be able to send 1080p video though these devices?
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  5. #65  
    Senior Member Alex Lubensky's Avatar
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    Read this one regarding ground and two power sources in PC tech:
    https://arduino.stackexchange.com/qu...sharing-ground

    Real life example of two different batteries for a monitor and a camera:
    https://steadicamforum.com/index.php...topic&id=20720

    Also page 31 of this doc is exactly about our case:
    https://web.mit.edu/jhawk/tmp/p/EST0...ps_handout.pdf
    Last edited by Alex Lubensky; 04-18-2021 at 01:36 PM.
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  6. #66  
    Senior Member Robert Hofmeyr's Avatar
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    Quote Originally Posted by Alex Lubensky View Post
    Read this one regarding ground and two power sources:
    https://arduino.stackexchange.com/qu...sharing-ground
    Interesting. Thanks Alex. I'm not sure if having 2 different power sources and connecting their grounds via the SDI cable can result in a potential difference across the cable large enough to do damage to the camera?
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  7. #67  
    Quote Originally Posted by Robert Hofmeyr View Post
    On a thread in the Red Komodo Users FB group, this isolator was suggested to prevent this issue: https://www.bhphotovideo.com/c/produ...isolation.html. Can anyone here confirm that this will work?

    I can't find it locally though, but I did find some much cheaper CCTV isolators like this one: https://www.communica.co.za/products...p-isolator-iv2. Will this help?
    Hi man, i asked myself the same thing since for 200 bucks one could also replace all the dtaps by lemos :D

    I found the same adapter you posted on ebay (shortened link -> https://rb.gy/x6dad5 ), with a little more details and also some others and started comparing.

    Based on the following articles I think there are different SDI protocols: HD-SDI (the one we need) and then there is EX-SDI, HD-CVI, HD-TVI, HD-AHD (and maybe others).

    https://www.supercircuits.com/compar...-video-formats
    https://www.clintonelectronics.com/w...-hd-sdiex-sdi/

    On the back of the product (ebay link above) it says AHD 720p 1080p, TVi 720p 1080p and CVI 1080p. Also in the product description it says "Compatible with all HD-CVI,HD-TVI,HD-AHD", therefore no HD-SDI.

    On the facebook thread you mentioned by now Jim Skinner has also posted a cheaper model:

    https://www.bhphotovideo.com/c/produ...d5p1ZFchvNds00

    Would be cool if everyone can chip in and share their solutions. Best of luck to all of you :D
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  8. #68  
    Senior Member Robert Hofmeyr's Avatar
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    Quote Originally Posted by Amarin Spörri View Post
    Hi man, i asked myself the same thing since for 200 bucks one could also replace all the dtaps by lemos :D

    I found the same adapter you posted on ebay (shortened link -> https://rb.gy/x6dad5 ), with a little more details and also some others and started comparing.

    Based on the following articles I think there are different SDI protocols: HD-SDI (the one we need) and then there is EX-SDI, HD-CVI, HD-TVI, HD-AHD (and maybe others).

    https://www.supercircuits.com/compar...-video-formats
    https://www.clintonelectronics.com/w...-hd-sdiex-sdi/

    On the back of the product (ebay link above) it says AHD 720p 1080p, TVi 720p 1080p and CVI 1080p. Also in the product description it says "Compatible with all HD-CVI,HD-TVI,HD-AHD", therefore no HD-SDI.

    On the facebook thread you mentioned by now Jim Skinner has also posted a cheaper model:

    https://www.bhphotovideo.com/c/produ...d5p1ZFchvNds00

    Would be cool if everyone can chip in and share their solutions. Best of luck to all of you :D
    Thanks Amarin!
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  9. #69  
    Senior Member Robert Hofmeyr's Avatar
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    Quote Originally Posted by Alex Lubensky View Post
    Also page 31 of this doc is exactly about our case:
    https://web.mit.edu/jhawk/tmp/p/EST0...ps_handout.pdf
    I looked at page 31. It does indeed refer to two independently powered devices connected by a video cable and having different ground voltages. But I think the voltage difference here is minimal (measured in mV) and it causes signal interference but does not fry boards. Once again, I must stress that I am no expert. I'm just trying to understand this better.
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  10. #70  
    Senior Member Blair S. Paulsen's Avatar
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    Nice find Alex. Pardon the pun, but the answer seems to be a common ground.

    Evidently, folks who have pre-wired their rigs so that monitors and other AKS share the same ground path as the camera avoid issues.

    Perhaps the greater incidence of problems with Komodos is because DSMC2 monitors are powered from camera pins, vs external monitors on Komodos using their own batteries/sources.

    FWIW, it seems like running both camera and monitor from the same power source would sort this issue in most cases. That said, don't blame me if you fry anything ;-)

    While the SDI failure is grabbing the attention, it's just the closest point of failure - not a cause. If you aren't creating voltage spikes looking for ground, then, theoretically, the SDI boards, connectors, cables, etc are immaterial.

    D-tap splitters anyone...

    Cheers - #19
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