Welcome to our community

Be a part of something great, join today!

Register Log in
  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

The SDI issues

Robert Hofmeyr said:
On a thread in the Red Komodo Users FB group, this isolator was suggested to prevent this issue: https://www.bhphotovideo.com/c/product/843846-REG/allen_avionics_hd_vit_75_video_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/cctv-ground-loop-isolator-iv2. Will this help?
Click to expand...

All these devices kill the "12G" signal though. That's the issue.

JB
 
Alex Lubensky said:
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.
Click to expand...

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.
 
Last edited:
Robert Hofmeyr said:
On a thread in the Red Komodo Users FB group, this isolator was suggested to prevent this issue: https://www.bhphotovideo.com/c/product/843846-REG/allen_avionics_hd_vit_75_video_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/cctv-ground-loop-isolator-iv2. Will this help?
Click to expand...

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
 
Amarin Spörri said:
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
Click to expand...

Thanks Amarin!
 
Alex Lubensky said:
Also page 31 of this doc is exactly about our case:
https://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
Click to expand...

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.
 
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
 
I'm still not understanding why there would be a large potential difference between the ground of a monitor and that of the camera if they are powered independently. But if this is the case, wouldn't just connecting the two grounds sort out the problem? And if the monitor and camera are both metal and have chassis grounds, wouldn't they be connected already if the monitor is mounted on the camera?

Edit: also, if this is the case, then the order of connection will make no difference, since the potential difference between the camera ground and monitor ground will still be there after the batteries are connected. And if the positive of the monitor battery makes contact before the ground it will not have an effect, since no circuit is formed.
 
Last edited:
Part of the problem is that the equipment being plugged into these cameras isn't...errr...like what get's plugged into more expensive cameras. It's not the same kind of well designed consistently performing (electrically speaking) equipment as more expensive RED camera users would be using.

People are using lesser known(for quality) accessory brands, lower cost items, commensurate with the price of the camera. Therefore, I think it's why you're also seeing more issues. Directly powering from a battery instead through power regulation.

Cheaper, less well designed and built stuff running from direct power from a battery and no ESD protection because it messes with the spec of the port. And while in THEORY you can't short out the centre pin, I've seen poorly made SDI plugs where you could conceivably do just that when connecting if you're not careful.

JB
 
Here's a summary of what we have learned if we want to avoid blowing the SDI:

- Only use high quality 12G-SDI cables
- Don't power your monitor via d-tap
- Don't power your monitor from it's own battery
- Don't connect or disconnect your monitor's power cable while an SDI cable is connected
- Don't connect or disconnect the battery on your monitor or on your camera while an SDI cable is connected
- Don't connect or disconnect an SDI cable while the camera is running
- Only use high quality monitors
- Do buy an inline SDI isolator and keep it attached to your camera

:)

Edit: the thing that is confusing me here is that some people are saying this is a ground loop issue (only happens when camera and monitor use same power source) and others are saying it's a differential grounding issue (only happens when camera and monitor use different power sources). This makes it very hard to protect against. It would help a lot if we knew if it is one of these issue or both of them.
 
Last edited:
Hi everyone,

I have prepared a rather specific question and would love to get some insight from you guys if possible. (maybe this will also clear up some things for someone else?):

So I originally I planned on using the d-tap out of a budget v-mount plate to power my komodo (when it arrives). Because of the whole d-tap safety issue discussion I'm thinking of replacing my d-tap splitter with one for lemo such the following one and also switching the d-taps on my cables out for Lemo 0B 2 pin connectors.

https://www.bhphotovideo.com/c/product/1600677-REG/camvate_c2566_1_to_3_power.html


Because the V-mount plate still has d-tap I'm considering to buy this safetap connector from Lentequip and replace the lemo out of the splitter with it.

https://lentequip.com/products/safetap

Sice there are more expensive v-mount plates with fuzes, regulators, esd and lemo from the start, I wanted to ask if this, also combined with a sdi galvanic isolator, could be a cost effective (and small) alternative to get a similar protection (like a D-Box from Wooden Camera for example). Or would I still be compromising on safety this way?
So regarding to power damage, is there anything else that can happen to a Camera than the sdi port getting fried (which there are methods to prevent), when using budget, non regulated v-mount power? (Btw with the lemos coming out the safetab obviously I'll only connect accessories that can handle the various voltage or else I'll put a voltage converter cable there)

Does anyone know if things like overcurrence or power spikes or something else can happen with a v-mount that can damage the cam and other accs? If so, what are those? Any stories or experiences?

Thanks

Also @ Robert Hofmeyr, thanks so much for your Summary above, I think this was a great idea and will help a lot of people! If you have a moment can you explain why only to use high quality monitors? (I have a cheap one :P). Does a galvanic isolator help in this regarad, also could the above mentioned safetap help maybe (by preventing power spikes while powering the monitor e.g.) ? Thx again mate ��
 
Common ground

Common ground

Any accessory, including monitors, needs to be properly grounded and shielded internally or all bets are off. A low cost monitor that has poor image quality, but robust electrical circuits is no larger risk than a high end monitor. That said, how many monitor reviews have you read that dove into such issues...

IAC, in terms of rigging power, the best insurance would seem to be a common ground for everything. That way, whatever causes it, power blips have somewhere safe to go. That's my plan anyway.

Cheers - #19
 
As I understand things, the issue arises when the SDI cable is connected first and the positive pole of the battery, or battery connector, makes contact before the ground (negative) connector. So, the immediate conclusion is to remove the SDI cable before connecting battery power, whether it's to the camera or to the monitor.

All this being the case, the simplest solution, as well as the cheapest, is to install an on/off switch inline with any external monitor and its power connector. As long as the switch is turned off it's not possible for the positive pole of the battery to make contact to any ground loop before the negative pole of the battery makes contact. Zacuto sells a d-Tap power connector with a built in on/off switch.

I have a micro on/off switch on all my external Dtap power supplies. Knock on wood, but, I've never had a problem over years of use this way.
 
Bill Ravens said:
As I understand things, the issue arises when the SDI cable is connected first and the positive pole of the battery, or battery connector, makes contact before the ground (negative) connector. So, the immediate conclusion is to remove the SDI cable before connecting battery power, whether it's to the camera or to the monitor.

All this being the case, the simplest solution, as well as the cheapest, is to install an on/off switch inline with any external monitor and its power connector. As long as the switch is turned off it's not possible for the positive pole of the battery to make contact to any ground loop before the negative pole of the battery makes contact. Zacuto sells a d-Tap power connector with a built in on/off switch.

I have a micro on/off switch on all my external Dtap power supplies. Knock on wood, but, I've never had a problem over years of use this way.
Click to expand...

Good idea.
 
Michael R said:
Thanks, Rob. There were no active swaps and the camera was powered down as we were moving from an AC-powered setup on sticks to a v-mount powered setup on gimbal. We filmed the interview (monitor working fine), powered everything down, unplugged AC, unplugged SDI, mounted the Komodo to the RS2, mounted monitor to the RS2 left handle, reconnected SDI, no signal. Tried different cables, different monitors, different batteries, everything. Never got a signal out of the SDI port again.


Just submitted a support ticket to Red so I'll update you when we hear back.
Click to expand...

"..powered everything down, unplugged AC, unplugged SDI.."
Betting it was unplugging the AC before unplugging the SDI?

I have never burned a port but I keep everything powered off a single gold mount battery on the back of the camera using a TILTA plate. I did recently get a power cable with 2-pin LEMO to power my TVlogic but I used the p-tap beforehand and always left everything plugged in and just power the camera and monitor down before swapping batteries.

Would be great to hear if these practices are considered safe.
1) Powering everything off the same power source?
2) Using 2-pin LEMO to power monitor?

So far so good but it's a little scary hearing about this issue.
 
Amarin Spörri said:
Also @ Robert Hofmeyr, thanks so much for your Summary above, I think this was a great idea and will help a lot of people! If you have a moment can you explain why only to use high quality monitors? (I have a cheap one :P). Does a galvanic isolator help in this regarad, also could the above mentioned safetap help maybe (by preventing power spikes while powering the monitor e.g.) ? Thx again mate
Click to expand...

Hi Amarin. My list was a bit tongue-in-cheek: it would be very hard to follow all those rules, and impossible in most production environments.

The truth is we don't seem to be entirely sure what causes the SDI to fail. If the problem is ground loops, then using a separate battery should prevent it, but it seems people powering their monitor from its own battery have also had the issue (there may be some confusion because I have also heard of BNC port issues where the inner petals in the port get bent). If the problem is more prevalent when users are powering their monitor from its own battery, then it is not a ground loop causing it, but it could be a result of the different potential of the two negatives. At this point only Red knows the number of failures and whether they are primarily from the ground loop issue or something else.

I don't see a problem powering the Komodo via d-tap. The ground loop is formed when you connect an SDI accessory via a cable to the same power source as the camera and the positive makes contact before the ground. This is most likely to happen with a d-tap connector. Now, if your monitor is also powered by the same battery (via a d-tap splitter) there will be a small risk of a ground loop whenever you plug in the second d-tap while your SDI cable is connected. This is not a huge issue because I assume you will not be plugging and unplugging these d-taps very often, so you can just disconnect the SDI cable before plugging in your power. Alternately, plugging the camera and monitor into the splitter before plugging the splitter into the plate should also prevent the ground loop.

I'm not sure if the safetap will prevent a ground loop - seems it's primarily for reverse polarity. Perhaps email the manufacturer and ask if output on the positive connector is prevented until the ground connector makes contact?
 
Amarin Spörri said:
Because the V-mount plate still has d-tap I'm considering to buy this safetap connector from Lentequip and replace the lemo out of the splitter with it.

https://lentequip.com/products/safetap
Click to expand...

According to this article, the SafeTap doesn't actually protect against this specific fault! It protects the accessory from reverse polarity but it does not help the sensitive SDI problem.

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.
Click to expand...

Via https://rencherindustries.com/blogs/technical-advisories/hot-plugging-devices-on-arri-cameras
 
Last edited:
You must log in or register to reply here.
Back
Top