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HD SDI causes short circuit? Letus Helix

Stefan Scherperel

Stefan Scherperel

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This is a new one for me tonight.
I was setting up my letus Helix single axis on my steadicam tonight. I had my Small HD AC7 Monitor connected via SDI to the Letus Helix SDI. The epic was being powered off the Letus helix. I go to connect the SDI cable from the Epic to the Helix slip plate, and everything shuts off. First I tested the camera!!!! Camera is fine, monitor is fine. Helix is dead, no power.
I have already contacted the company, but they won't be open until the morning, but I can't even figure out how this would happen. Does SDI carry power? If so that is news to me. I've been hot plugging HDSDI cables for years without issue.
Anyone got any ideas?
 
Update: Well, havn't figure out what happened yet, but I wanted to say that I just got a call from the Letus rep, 8:30PM and she is sending me a shipping label and has told me that they will diagnos, fix and have the letus back to me by the end of the week. So despite the very odd occurance with the SDI cable, Letus Customer service so far is top notch.
 
I recall a weird wiring on the small HD power connector.
I recon the ground on the monitor is hot because of the reversed polarity on the small hd power connector.
you plug in SDI and you short the hot ground to the shield/ground with the rest of the unit.
Hence it dies. I would look at the power cable for the monitor....
 
But if it were an issue with the Small HD monitor, wouldn't it do the same thing to the camera? I've been using that monitor connected directly to the camera witout issue. In fact, I tested the monitor once again connected directly to the camera without issue.
I'm still surprised that current even flows with the SDI signal. Thanks for you input Jacek
 
sometimes connecting my blackmagic to the helix would short the helix out. Sometimes it can be replicated and sometimes it can't be. Will be looking into the issue soon.
 
So it turns out the problem was in the D tap on the battery plate. Still not sure why it decided to blow when I connected the SDI cable, but it looks like it just blew the fuse on my D tap battery plate. The V mount Battery plate was powering the Helix and Epic, which seems to be the absolute max of the D tap. When I connected the SDI cable there was a little spark and then loss of power. I didn't realize the the fuse had blown on the plate (easy to replace). I still don't know what the SDI has to do with any kind of power draw but evidently the fuse didn't like that. I have remedied the situation by purchasing the Helix batteries x3, plus 2 chargers, so I will be powering off of that system from now on.
 
Is it possible that the EPIC started to draw more power once the SDI was activated?

I don't know if the EPIC powers the debayered SDI output unless something is connected but it's possible that once it had to do that extra process it drew an amp or two more than the d-tap could provide...
 
That definitely makes sense. Not sure how all that works. just glad that I don't have to worry about plugging in SDI cables (fingers Crossed) in the future. Always a heart stopping moment when something like that happens and you have to go through gear bit by bit to make sure everything still works.
 
SDI cables don't carry power, but the screen is often earthed/connected to metal chassis of equipment.

A spark can happen if two bits of equipment happen to be at different earth potentials before connection, or if there is a static charge on one.
 
Hmmmmm, very interesting, because that is exactly what happened. Small spark, everything went dead, although it turned out the only thing damaged was the fuse.
Different earth potentials meaning grounding? Is there a way I can prevent this in the future?
 
A few months back, I was powering an Epic off the Helix and the voltage would drop. Long story short, with help from the guys over at Du-All Camera, they figured out it was the letux power cable. It was too long and thin to carry all that power, hence the voltage drop. Since then, Letus made a newer cable, shorter and thicker that's able to carry the necessary voltage.
 
Eric, thanks for the article, this is all starting to make a lot more sense. I've been working full time in the industry now for 10 years, and this is the first time I've come across this particular problem. I'm no electrician, but hopefully I can avoid another situation like this in the future. Luckily this happened while I was testing gear in my studio (which is why I test all my gear to begin with) and not on location. I'm definitely keeping that article around for future reference.
 
Savva, where you powering off the Letus Batteries or another battery source.?I just ordered a whole bunch of Letus Batteries and Cage to power things off of now, so I'm hoping all works out well.
 
I'm currently having a similar issue but without the Helix involved:

I have my V-mount plate attached to my camera. It powers the camera fine via the cable attached into the v-lock plate.
I then attached a d-tap cable to my v-mount plate and then to my monitor a spark occurs. Camera turns off.

I try the monitor alone through another battery with the same cable and it is fine.
I try the monitor through the battery when it is connected to the camera and it sparks.
Is the v-mount battery plate causing this problem. As the d-tap ports on the plate do not work now, but it will still power the camera through the red power cable.

Update:
As an update it only happens when I have the HD-SDI or HDMI cable plugged into camera and monitor.
It won't spark if the HD-SDI cable is not attached.
Happens on both my Epic and Scarlet cameras with same plate. So it can't be a fault with both HD-SDI ports or shorting from inside the camera.
Problem does not occur when I power monitor separately and camera separately with 2 different batteries.

Thoughts?
Is the v-mount camera plate causing this problem.

Update 2:
I've changed v-mount plates and it still does it. I'm wondering if it is a monitor problem. Video Devices Pix-E5. Could it be?
The v-mount plate I changed it with is the same brand, X-Pro GP-S originally brought back in the day through Wooden Camera.
Replaced fuses inside v-mount plates but problem still occurs and v-mount plate fuse burns out.


 
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Thats unfortunate, SDI is generally low voltage (really, you would probably be more likely go get a short from HDMI)
 
I'll let you all know if I ever solve the problem.
I think it is a plate problem.
So I'm going to try that solution first. I have written to Video Devices to see if they have come across any other problems with either of their new monitors.
As that DC Jack isn't the best power connection.
 
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