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Old February 20th, 2012, 11:37 PM   #1
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Wiring a 4-pin XLR for AC power?

From time to time I use a Smith-Victor SV-840 light, sometimes on-camera, sometimes on a stand.
I've lost the AC-to-4pin XLR cable, which is very helpful when using it as fixed lighting.

I can't find a replacement, and want to make one, but I don't know the pin connections.
Does anyone know how to wire a replacement? Or where I can get one?
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Old February 20th, 2012, 11:57 PM   #2
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Re: Wiring a 4-pin XLR for AC power?

hi denis

4 pin canon xlr plug only pins 1 and 4 used

pin 1......... ground

pin 4......... +12volts

plugs should be available from any electronics store


cheers

Last edited by Ian Dart; February 21st, 2012 at 01:16 AM.
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Old February 21st, 2012, 12:53 AM   #3
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Re: Wiring a 4-pin XLR for AC power?

ALERT! ALERT! .. Folk in the NYC Metro area should keep their eyes peeled for a bright flash.

Dial blah blah blah etc.

That is, unless you know how 110V AC gets reduced to +12V in a single cable.

Cheers.
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Old February 21st, 2012, 01:10 AM   #4
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Re: Wiring a 4-pin XLR for AC power?

i assumed denis had the good sense to only use 4 pin xlr's with 12 volt power sources........
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Old February 22nd, 2012, 02:35 PM   #5
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Re: Wiring a 4-pin XLR for AC power?

Thanks for your responses, but now I'm scared and confused. I noticed that Ian's response indicated +12V and that made me take a closer look.

Here's a better description of the cable I need:
On one end is a typical 2-prong, non-polarized AC plug (with 18 AWG wire) capable of plugging into any 110-120VAC outlet.
The other end must be a 4-pin female XLR plug of the type where the 4 pins are in a curved, half-moon-like configuration, (as opposed to the pins being in a square or rectangular configuration).

The female XLR plugs into the coiled cable of a Smith-Victor SV-840 on-camera lamp. That particular model of lamp allows it to be used with either 12V DC or 120V AC, as long as the proper voltage bulb is inserted to match the power source. On this particular lamp, when using AC power, a bulb up to 300 W can be used, while on DC power, the max wattage of the bulb can be 100 W.
The description & specs can be found here:
Smith-Victor SV840K AC/DC Video Light Kit and Charger 401141 B&H

Upon closer inspection, I realized both the female and male XLR connectors actually unscrew, allowing me to see exactly how they are wired. Both have the 18 AWG wire soldered to pins 1 and 4, so Ian's advice seems correct.

If this still seems dangerous to you, please reply. I don't need to go "burning down the house."

Thanks again.
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Old February 22nd, 2012, 03:02 PM   #6
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Re: Wiring a 4-pin XLR for AC power?

NO NO NO
There is a bit missing - the camera needs a 12V DC input not mains voltage AC, as in what comes out of the wall.

Various types of power supply exist. Some are similar to a laptop PC PSU, a small grey or black box with ac in one end and DC out the other. Some PSUs are more robust in heavy cases. What is 100% certain is that a camera with a 4 pin XLR does NOT UNDER ANY CIRCUMSTANCES connect to the AC power, and the joke about lighting up isn't a joke at all. A pop, maybe a bang and a VERY expensive repair - or potentially (no pun intended) a write off if the damage spreads beyond the DC fuse.


You need 12V (well, 13.8 actually) and any kind of DC power supply that can manage that voltage will probably be fine.
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Old February 22nd, 2012, 03:36 PM   #7
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Re: Wiring a 4-pin XLR for AC power?

Paul,
I appreciate the quick response, and your advice and concern for my safety and equipment, but my questions pertain to powering an external, camera-mountable lighting fixture...not powering a camera.
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Old February 22nd, 2012, 03:55 PM   #8
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Re: Wiring a 4-pin XLR for AC power?

hi denis,
i checked out the link and am not sure how they supply the ac mains power to the light........
it definitely has a 4 pi xlr connected to the light. for an on camera battery driven light this is pretty standard.

is there another input plug on the light for mains power........ ?

under no circumstances would i run mains power through a 4 pin xlr. it would be extremely dangerous......

4 pin xlr plugs have been the industry standard for supplying 12 volts on professional gear since
the eighties and most eng cameras would run on a voltage range of 10.6v to 18 volts.

the wiring of the pins has been standard since then.

pin 1...ground

pin 4.....+12v

cheers
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Old February 23rd, 2012, 04:47 AM   #9
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Re: Wiring a 4-pin XLR for AC power?

Looking at the spec of the lamp is does look like the 4 pin XLR is used to do either DC 12 volt or AC 120v.

You need to change the bulb to use either DC or AC at the chosen voltages but I would imagine the wiring will be the same for both with the two pin mains connector going to pins 1 and 4 of the XLR.

LIke others I would question the safety of putting AC 120v down a 4 pin XLR type connector and personally I would not do it but I suggest you call the manufacturer to confirm that the lamp has it's safety certificate to do this.

Better safe than sorry: http://www.smithvictor.com/company/contact.asp
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Old February 23rd, 2012, 05:41 AM   #10
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Re: Wiring a 4-pin XLR for AC power?

looking at the lamp, the cable from the xlr plug to the lamp head is two core.
which means no earth termination on the lamphead.

not sure if they are correct in saying it can run on ac. if it shorts out while
on your camera you can kiss your camera goodbye if you are still alive.

i wouldnt touch it with a 40 foot barge pole.........

xlr plugs are not rated or designed for 240/120 volts.

cheers
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Old February 23rd, 2012, 05:46 AM   #11
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Re: Wiring a 4-pin XLR for AC power?

Last week I used a Marshall monitor on top of a JVC HD250. Both off of 120AC main supply. The cam ran off an AB charger/power supply using a 4 pin cable from the charger/power supply to the cam and the monitor did the same, used a 4 pin cable to the power supply THRU a converter supplied by the manufactuer. Certain products like Bescor have lights that require changing of the bulb to go from AC to 12v. Certain other products use a converter. That's the piece that's being left out of this equation. It's obvious you can't just wire a 4 pin cable to a plug that goes to a 120v AC plug so...where's the converter?
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Old February 23rd, 2012, 07:03 AM   #12
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Re: Wiring a 4-pin XLR for AC power?

I would understand a 120v AC to 12v DC convertor if the light always used DC 12v bubbles but this one seems to use 120v bubbles direct and therefore must be putting 120v AC through the 4 pin XLR.

I also would not be happy to be using this light if it is putting an un-earthed 120v AC current through a 4 pin XLR.

According to this spec the rated voltage for XLR connectors is only 50v AC : http://www.dem-uk.com/deltron-compon...05-713iss6.pdf
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Last edited by Gary Nattrass; February 23rd, 2012 at 08:28 AM.
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Old February 24th, 2012, 10:42 AM   #13
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Re: Wiring a 4-pin XLR for AC power?

The light itself may accept AC and DC lamps but I do not believe an XLR connector is approved for use with AC power. If someone can document otherwise please post a link.The OP might contact the light's manufacturer for advice as well. I suspect they will err on the side of safety. Better for you to go away mad than injured, or worse.
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Old March 9th, 2012, 12:24 PM   #14
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Re: Wiring a 4-pin XLR for AC power?

Here's something for future reference for other owners of the Smith-Victor SV-840 AC/DC light:

I like the versatility of this light, i.e. either 120V AC or 12V DC, but the kit comes with a handful of different connectors that are easy to misplace or leave behind at a shoot. (Which seems to be exactly what I did, and I suspect I may not be alone).

I actually have 2 of these lights, and before proceeding, I unscrewed the XLR plug for the one XLRF-to-AC cord that I still have and examined it closely. The AC power cord is, indeed, soldered directly to pins 1 and 4, exactly as Ian described. (I didn't realize the connectors came apart so easily until after I'd read everyone's warnings, and don't know why I didn't do this earlier...Duh! Can I claim temporary insanity? I've soldered many connections in the past, just never on an XLR connector. I'll chalk up my stupidity to fear of damaging the light or starting a fire).

However, before I would run the risk of frying myself or one of the lights, I also took Gary's advice and called Smith-Victor. Per the person I spoke to (who put me on hold for only a few seconds and also checked with someone in another department), a 4-pin XLR will handle 120V AC current. (I bought a Newtrik connector to do the job). The important point is to make sure that I'm using the correct voltage bulb for the power source (which I've always been careful to do). So Gary's observations about the bulb type were also correct...thank you, Gary.

Other concerns important to creating this replacement cord are:
1) to make sure the 2-prong AC cord is non-polarized, and
2) to make sure the AC cord is of sufficient gauge/thickness and insulation to handle the load.
While I may not be able to obtain the exact same cord, here are the details printed on it:
VL-1 TECHPOINT CSA LL109448 SPT-2 (18AWG) 0.824MM2 [sqUared, or to the 2nd power]/2C 60[DEGREES]C 300V FT2 -LF-

At the moment, I plan on using 1 of these lights with 100W 120V AC bulb as a fill light on a stand in a 3-point setup, (I've already bought the hot-shoe-to-stand adapter), but am not sure if a Lowel Omni w/500W FTK bulb and full scrim will be too strong for a key light. (I also have a Lowel DP light, but have only 1000W bulbs for that, which seems like entirely too much for a 1-person, on-location interview). We'll be shooting for less than an hour, but I'm still concerned about the heat these things will generate.

Thanks again to everyone for their advice, contributions, and concern about my safety. Maybe this thread will be of help to others in the future.

If/when I try this out, I'll wear heavyweight rubber gloves and keep a fire extinguisher handy, and report back on my success or failure.
"Thanks for watching."
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Last edited by Denis Danatzko; March 9th, 2012 at 12:31 PM. Reason: Addendum:
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Old March 12th, 2012, 05:41 AM   #15
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Re: Wiring a 4-pin XLR for AC power?

fair enough denis.
i would still be very careful running line voltage through the plug
when you took it apart you will have noticed there is not much room
inside, and no insulation, the pins are easy to bend out of shape and if they contact
the casing it wouldnt be pleasant.

when you use it place a portable RCD safety switch between the mains outlet
and the light for your own safety.

i have been a gaffer for 12 years and there is no way i would allow one of
those plugs near my truck.

cheers mate
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