Danger Using External Battery Plates (V-mount, Etc.)

J

Jim Ritscher

Well-known member
If you are using a multi-voltage battery plate (either V-mount or gold mount) you should be aware that some of them such as the Tilta one can fry your equipment. This was mentioned in another thread, but you might not have seen it. These battery plates typically allow you to supply the following voltages 18.4 (the direct battery voltage), 12V, 7.2V, and 5V. There is a switch to turn on the regulators that supply all of the voltages (except the 18.4V). If you turn the switch OFF, you can measure a significant voltage (approximately 14V) between the grounds side of the 18.4 and the outside of the barrel connectors for all of the other voltages. This voltage goes down over time, so I suspect it's the result of a capacitor charge.

The outside of the barrel connectors are usually connected to ground in the equipment they are attached to. The net result is that you have the potential to have drastically different ground voltages running around. If you connect, say, an SDI connector to the Odyssey 7Q and Alphatron EVF, people have reported that their Alphatron gets fried. Presumably the shield part of the SDI connector is transmitting voltage.

Possible solutions: 1. Disable switch. 2. Never turn it off (Maybe tape it in the on position). 3. Find a way to fix the problem in the voltage source. 4. Find a unit that doesn't have this problem.

See my post further down for more information.
 
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Thanks Jim, which thread was this discussed in? I was thinking of getting one of these, so any additional info in that thread would be good.
 
+1 That's a good catch (as i have a tilta plate too). I'd be interested in following this up with tilta themselves though - the original discussion would be very useful

thanks
Paul
 
I dont think the Movcam has a switch? I was probably leaning more towards that anyway although haven't ruled out the Tilta yet.
 
I've got the Tilta plate too, although I mostly use it just as a counterbalance as I've found the power it supplies is very sensitive to knocks.
 
Titla here too, but I really only use the Dtap and 12V ports on it anyway. Don't run the FS700 off it. Really, the battery life the FS700 gets is pretty amazing. I only use the Vmount to power the odyssey/alphatron/audio mixer.

2 970s and one 98w Vlock last all day.
 
Colinelves said:
I've got the Tilta plate too, although I mostly use it just as a counterbalance as I've found the power it supplies is very sensitive to knocks.
Click to expand...

Thats not good! Has it got a dodgy connection or is the battery plate to battery connection a bit loose?
 
If you do a Google search (not the search inside the forum) on "Tilta power problem" you will get a whole series of references, particularly on the black magic camera forum. Note that it doesn't only apply to Tilta power plates. I have the same problem with another Chinese manufactured plate. I would suggest that anyone who has a power plate test it. Use a volt ohm meter. These start at about $10, and in my opinion everyone should own one. Put a battery on the plate. Insert all the cables, but don't connect them to any equipment. Turn the power on, then off. Setting your voltmeter to read 18 or 19 V (e.g., 20 V scale), test the voltage across the D-tap Outputs. This is just the direct battery voltage (It's hard wired to the battery connectors). Determine which side is negative. Put the black probe (negative) on the negative d-tap terminal, and test each barrel connection (the outside of the barrel) in tern. If things are correct, there should be no voltage whatsoever. If not, for example if you have say 14 V (as I do) then you have a potential problem. Note that you will get the problem when the switch has been turned off, not when it's on.

Note that the D Connector is wired directly to the battery. Therefore if you connect directly to the Odyssey 7Q using D-tap, this is not in itself a problem. (And you can leave the switch off, conserving power.) Likewise, if you have a device connected to any one of the separate power sources, this is also not a problem, and you can use this switch normally: i.e., turn it on when you need the power. The problem comes when you have more than one device connected to the power plate. Because there's a difference in ground voltage, the SDI (etc.) cable can carry enough voltage (okay, current actually) on it to fry a piece of equipment. The metal connector of the SDI cable should also be at 0 V. When the grounds of different pieces of equipment have different voltages on them, this is known as a ground loop problem. Ideally, all the grounds should be at the same voltage (i.e., 0 V relative to each other).
I've gone a little technical in this explanation because I found it frustrating to read the other threads and not know what the actual problem was.
 
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