View Full Version : Wiring a 4-pin XLR for AC power?
February 20th, 2012, 11:37 PM
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?
February 20th, 2012, 11:57 PM
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
February 21st, 2012, 12:53 AM
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.
February 21st, 2012, 01:10 AM
i assumed denis had the good sense to only use 4 pin xlr's with 12 volt power sources........
February 22nd, 2012, 02:35 PM
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."
Paul R Johnson
February 22nd, 2012, 03:02 PM
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.
February 22nd, 2012, 03:36 PM
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.
February 22nd, 2012, 03:55 PM
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.
February 23rd, 2012, 04:47 AM
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
February 23rd, 2012, 05:41 AM
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.
February 23rd, 2012, 05:46 AM
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?
February 23rd, 2012, 07:03 AM
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-components/Data/Product_Downloads/701-709-705-713iss6.pdf
February 24th, 2012, 10:42 AM
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.
March 9th, 2012, 12:24 PM
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."
March 12th, 2012, 04:41 AM
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.
Paul R Johnson
March 12th, 2012, 06:48 AM
I'm really confused. The device in the pictures is clearly a 12V lamp, with the usual 12V 4 pin XLR connector, plus and adaptor that has a car type 12V connector to fit into the 12 cigarette type output connector on the battery. There is NO picture I can see of the power supply - which no doubt connects to the battery pack with a dedicated connector. Have I completely missed something here? This kind of power supply arrangement is really common - and when the product is sold here in the UK, it is with a 230V ac unit rather than the US voltage unit. The battery is the same, the 12V connectors are the same, and so is the car type socket. This PSU change is the standard economic way to provide power to charge a 12V pack! The lamp you can buy as a replacement is also of course 12V.
Where is everyone seeing stuff that is getting them so excited? I see nothing at all that worries me here - just a 12V portable light running off a low voltage battery source.
While there was a mains version of the XLR connector, it was a very different type with red insulation and a very different application style. While popular with the BBC here in the UK, it didn't really take off on non-professional products.
This is the charger - which clearly uses the 12 automotive style socket as the means of charging the battery.
The only worrying information I can find is that there is a 120V AC lamp available, and this does seem to be powered via the XLR-4 connector. The connector, or at least the Neutrik version is capable of being used at 120V, although here in the UK, it's quite possible a person skilled in testing might decide that the connector is NOT suitable for our mains voltage and fail the item as also not having appropriate insulation.
Low voltage seems no problem, but I really do have issues with using what are almost known as standard 12V power connectors being used for much higher and destructive voltages. Maybe not against US law, but a damn stupid practice with very expensive side effects. I for one, seeing a dangling 4 pin XLR would assume I could plug it into the camera that has the same connector - a very expensive mistake.
March 12th, 2012, 07:03 AM
I think you basically put a 120v bulb in and connect the 4 pin xlr to a mains outlet to 4 pin cable. Scary as the whole lot will be totally un-earthed!
We had those red mains XLR's at Tyne Tees TV for a while in the 80's but I thought they had been banned and one of our engineers managed to put a 3-pin audio xlr into the mains wall socket to prove the point! ;0)
March 12th, 2012, 06:44 PM
your last paragraph sums it up
from what i understood the manufacturer suggests using a cable with a mains
power plug on one end and the xlr on the other. this would involve running 120/240
volts through the plug. thats why i was excited (in a bad way)
it is very dangerous and it would not pass a test and tag test which makes it illegal in australia.
from experience i can say that mains power deserves all the respect you
can give it.
March 12th, 2012, 07:28 PM
FWIW, I built the replacement cord over the weekend. This was my first experience with soldering an XLR plug, and Ian was entirely correct: "...there is not much room inside, and no insulation... "
Before building it, I again closely examined the one cord that I didn't lose. This is exactly as it arrived with the lighting package when it was new, so I had something working on which to base my steps.
My examination revealed that each soldered connection was protected/insulated with black heat-shrink tubing. So, with careful insulation - and everyone's warning - in mind, I duplicated that set-up. Before soldering, I slipped on some very carefully-measured heat-shrink tube for each pin-to-wire connection.
I ended up using 16 AWG multi-stranded wire rather than 18 AWG, and had to use a typical/common 2-prong plug (the type where each wire is screwed to its' respective prong) for the mains end, because I couldn't locate a 10 foot cord with a molded-on plug.
I then went about soldering one wire to pin 1. Working with the short "barrel" for pin 1 took longer than I hoped, but I was going slowly, being careful not to damage the XLR innards. (I even stuck a probe into the receiving end of the pin 1 barrel to serve as a heat-sink and hopefully prevent damage to the XLR. Once soldered, I allowed it to cool for a couple of minutes, then slid the heat-shrink tub over the connection and used a heat-gun to shrink it to fit. That worked well.
Moving onto pin 4, which had a longer :barrel", I repeated the procedure, e.g. soldering, letting cool a bit, then slipping the heat-shrink tubing over the soldered connection and heating it to shrink. This too, worked well, and, in fact, went a bit faster and smoother than pin 1.
Next I slid some heat-shrink tubing over the cord to help fill the gap at the hole where the cord enters the plug. (Unfortunately, there was not enough room inside the plug to provide any strain-relief, and unplugging it would simply have put unnecessary presssure/strain on the soldered connections). I did this in 4 layers of heat-shrink, i.e. put 1 layer in place, then heated & shrunk that, then repeated that process 3 more times, with each layer of heat-shrink slightly shorter than the previous one.
I connected the wires to their respective prongs, made sure I had a 120V bulb in the lamp, donned my heavy rubber gloves, plugged the cord into the wall outlet, then turned on the lamp. It worked fine...no sparks, no blackouts, no tripped circuit breakers, no glow over Manhattan.
Here's a link describing the lights I own:
Smith-Victor SV840K AC/DC Video Light Kit and Charger 401141 B&H
Unfortunately, the photo doesn't show the AC-to-4-pin XLRF cord. However, if you check out the link, then click on the "What's in the box" link, you'll see mention of an AC to XLR adapter. It is that piece that I've assembled.
This light has been on the market for some time, and has received mostly good reviews at the B&H site. I'm confident I've at least replicated the cord that I used as my guide and, unless the manufacturer has been shipping unsafe fixtures for a few years now, expect to be able to return to using this lamp again both on and off camera.
Thanks again for everyone's concern, advice, and warnings. I'm not much of a gambler (particularly with my personal safety and my equipment), and appreciate all the advice.
Just so you all don't think I'm absolutely crazy, here's a link to the manufacturer's web site describing the fixture. Note mention of using AC power with a 10ft AC-to-XLR adapter.
March 19th, 2012, 07:26 PM
XLR's are pretty roomy inside... try a TA5 sometime.
anyway, I did have a AC Edison ->XLR4 for doing exactly the same thing- powering 120V bulb in a ProLight. I had not used a 12V bulb in that light in years, but still wanted the easy power option to do so. I eventually sold that light. while I had it, I never had the power cable off of the light.
you can tag / label the wire end if you want to make it more obvious... that said, the WORST connector I'd seen used for power was a XLR 3. why ? because they are cheap. however it WAY WAY WAY too easy to send power into a mic input and fry it... and if thats all you do you where lucky.
the big danger is mainly putting 120V into something that wants 12ish V and releasing the Blue Genie :(