Source Four Leko for Filmmaking - lamp burned out immediately

Joined
Mar 29, 2020
Location
Iowa
Hello all,

As title suggests, I bought a Source Four Leko 750 to use for indie filmmaking. I have some experience with these lights from working as a volunteer stagehand and periodically on film sets, but am by no means an electrician and feel like I'm in over my head. Saw lots of good info on this forum, figured some of you all could advise me how to move forward.

Within 15 minutes of getting the source four built in my living room, the lamp burned out. I had the light plugged into a 1000w impact dimmer, and was testing the dimming level when a flicker happened and the lamp died. To note, the dimmer added a noticeable hum to the light. The more I dimmed, the louder the hum.

Specs:
Source four leko 750 (purchased from usedlighting.com)
Ushio HPL Lamp (750w/120v)
Impact D-1000 AC Dimmer Control 15-Amps
Edison Plug (15amp/125v - I replaced the bates plug with this Edison from a local hardware store)

I have not checked the voltage of my apartment's outlets. Is that something I should have done? Will I need to do this with every outlet I use? (planning to use in residential houses for an evening sun effect).

I did not touch the bulb prior to placing in the S4, so oils should not have been the issue. Was this probably just bad luck, or am I doing something wrong? Do any of the parts I am using bring up red flags? I used the lamp for about 10 minutes without the dimmer and was not having any issues, my hunch says the dimmer might've had something to do with it.

Thank you for your time,
 

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FMEng

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Severe vibration from an unfiltered dimmer could certainly be a factor. Stage dimmers have inductors to smooth the waveform and reduce filament sing. Inductors are too big to fit in something made to fit in a standard electrical box.

It seems to me that an S4 for close range video is way, way overkill, and not well suited for video. If you dim it, the color temperature is going to shift drastically yellow, affecting the color of your results. Most video folks prefer, big, diffused light sources, with a stable color temperature. Fluorescent and LED are widely used for video.
 

Nic

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Sep 21, 2019
Location
St. Cloud, Minnesota
Like you, I’m not an electrician but here’s what I can tell you.
I agree with your assessment of the likely cause here. To expand on what FMEng said, the dimmer you have is a phase control dimmer. Basically, it switches the power on and off very quickly to “dim” the light. These are known to cause lamp sing and I’m not surprised it would cause filament damage.
What you really want is a sine wave dimmer which reduces voltage while still outputting constant power.
If you don’t want to buy a new dimmer, you might try a 575w lamp so that you’re dimming the instrument by a lower percentage (I don’t actually know if this will work, it’s only an idea). You could also use light modifiers like scrims instead of dimming.
 
Joined
Mar 29, 2020
Location
Iowa
Thank you all for getting back to me on this so quickly.

Regarding dimmers, could a simple solution be simply switching to a sine wave dimmer? There seems to be some cheap pre-made options online. Could something like this be a good alternative to the impact dimmer I have?: https://www.fullcompass.com/prod/15...taW_8P4lM-YipQSG92vwDhxJS8ranQrsaAqGsEALw_wcB

Regarding S4 lekos for video: I'm basing this mostly off David Mullen's work (Marvelous Mrs. Mazel being his best-known). He uses source-fours to create hard slashes of light. Easy to use indoors without a ton of spill on walls. Lots of other practical uses, too. If curious, see some examples here: https://cinegleaner.postach.io/page/day-int . For the price, I figured it was worth a try, as a joker 400/800 (commonly used) of similar power in a Leko attachment is around $5000.

Good point, Matt. Most of the time David has the leisure of a generator and isn't on house-power. I typically don't have a generator. would household electrical outlets be an issue here? Most of my other fixtures run off battery, so the S4 would be one of few fixtures I'd be plugging into a household outlet.

I will also pick up a 575w bulb. Scrims also a good call. I will usually not need full power, anyway.

Thanks!
 

theatricalmatt

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Joined
May 25, 2013
Location
New England
Hi Ben --

I believe the restriction on residential use has more to do with heat than electrical power, the same reason small halogen lamps in torchieres, so very popular when I was growing up, were removed from the marketplace. Between the heat off the lamp cap, and the heat from the beam of light -- at a much, much shorter throw than its intended use in a theater or soundstage -- it's very easy to start a fire. Houses also tend to have a lot more fabric (curtains, sofas, rugs, etc) than in a theatrical or architectural installation.

Power *is* a bit on an issue, as many household outlets may be rated at 15A, but the service shared between multiple locations in the same house. Or backed with only a 10A breaker, or run with only 18ga wire.... the problems are numerous, and household and apartment buildings get inspected much less frequently than commercial or industrial spaces. So please, please be careful.
 

BillConnerFASTC

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Jan 30, 2010
Location
Clayton NY 13624
I don't consider your use in a residence to be residential. Now, start using it for long periods to read a newspaper or prepare meaks, and that's probably a bad idea. The back end of an S4 against drapery would be not good.
 

microstar

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Jan 19, 2014
Location
Lawton, OK
Thank you all for getting back to me on this so quickly.

Regarding dimmers, could a simple solution be simply switching to a sine wave dimmer? There seems to be some cheap pre-made options online. Could something like this be a good alternative to the impact dimmer I have?: https://www.fullcompass.com/prod/15...taW_8P4lM-YipQSG92vwDhxJS8ranQrsaAqGsEALw_wcB

Regarding S4 lekos for video: I'm basing this mostly off David Mullen's work (Marvelous Mrs. Mazel being his best-known). He uses source-fours to create hard slashes of light. Easy to use indoors without a ton of spill on walls. Lots of other practical uses, too. If curious, see some examples here: https://cinegleaner.postach.io/page/day-int . For the price, I figured it was worth a try, as a joker 400/800 (commonly used) of similar power in a Leko attachment is around $5000.

Good point, Matt. Most of the time David has the leisure of a generator and isn't on house-power. I typically don't have a generator. would household electrical outlets be an issue here? Most of my other fixtures run off battery, so the S4 would be one of few fixtures I'd be plugging into a household outlet.

I will also pick up a 575w bulb. Scrims also a good call. I will usually not need full power, anyway.

Thanks!
From the few specifications available, there is no mention of the TecNec 43060-0VGA being a sine wave dimmer. I doubt it could be, considering its price.
 

DrewE

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Mar 18, 2019
Location
Vermont
Most theatrical dimmers are not sine wave dimmers, though they may (i.e. probably do) have better filtering than most residential dimmers. I'd also be inclined to suspect a bad lamp if nothing else obvious comes up to explain the problem (such as a bad socket or mechanical stresses/bumping), albeit without a ton of experience to base that inclination on.

One appropriate option for a sine wave dimmer is a variac, naturally taking care to get one with a suitably sufficient power rating. I would be very surprised if the TecNec unit is anything other than a typical phase control circuit, basically a beefy household dimmer or power drill speed control switch in a slightly different box.
 
Joined
Mar 29, 2020
Location
Iowa
Sounds like I need to do a bit of research. Going to look into an auto-transformer / Variac. Are these simple plug-and-play sort of dimmers like my phase control dimmer, or will I need additional equipment to use? (aside from getting the correct power rating, that is).

Glad to hear there's a chance my lamp was simply defective. I was moving the source-4 while the lamp was on. Perhaps that caused the lamp to burn out? That said, the burn out did not happen while I was making adjustments. Is it best practice to power down the lamp when going to make adjustments to height and angle? I'm using grip gloves so heat hasn't been a problem. Going to test out my second lamp tomorrow and hope the first was simply defective.

Thanks you all,
 

DELO72

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Aug 8, 2007
Location
New Hampshire
First up, the dimmer likely had nothing to do with it. You can easily use (and I have many, many times) a standard Lowes/Home Deport rotary resistance dimmer and it'll work fine (if rated for the right wattage).

Also- your home outlet provides plenty of power. Home outlets are 15A, 110-120V. (That's 1650-1800W max draw before you trip a circuit breaker). mind you- that's total draw from all outlets for that room, that are on the same breaker.

It's most likely you had a lamp with a weak filament that had taken rough shipment and was prone to failing as a result. Take a look at the contacts in the fixture's socket, and make sure those look good (brass looking vs. black or corroded.) so you can rule that out as a factor.
 

derekleffew

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Lynnchesque

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Feb 28, 2019
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East Bay, CA
It should be noted: It is common practice to adjust the pan/tilt, focus, and shutters with the light hot and on. It shouldn't be so fragile that those movements cause a failure.
 

RonHebbard

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Waterdown, ON, CA
It should be noted: It is common practice to adjust the pan/tilt, focus, and shutters with the light hot and on. It shouldn't be so fragile that those movements cause a failure.
@Lynnchesque With pan & tilt locks already loosed and all shutters pulled AND THEN the lamp illuminated at a maximum of 80%, I'm posting in full agreement.
Bad practice would be: Illuminating a stone cold lamp from 0 to Full in a 0 count AND THEN freeing its pan and /or tilt locks in a JARRING / SUDDENLY vibrating way and / or "debating" with a jammed / stuck shutter in your attempt to 'school ' / 'convince' it of the error of its ways.
Toodleoo!
Ron Hebbard
 
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