"As Arri" HMIs

[Evan Bourcier]

Hey guys! Been reading the forums for a while, this is the first topic that made me make an account though.

I've been watching to add some good daylight punch to my personal kit, and I love jokers but can't currently justify the cost. I found these Chinese knockoff HMIs on eBay and was curious if anyone has any experience with them. Obviously I'm sure they're nothing like high-end HMIs, I'm mainly just worried about safety with them.

http://www.ebay.com/itm/1-2KW-HMI-Fresnel-HMI-DayLight-Lighting-Electronic-Ballast-Dimmer-Lamp-AS-ARRI-/261188319914?hash=item3cd0097aaa:g:-SAAAMXQhuVRSSDJ

Additionally, are there any other cheaper HMIs that you would recommend instead?

Thanks,

Evan

 

[Bill DiPietra]

Welcome to the forum, Evan.

 

I personally don't have any experience with the knock-offs, but I know others in this forum have had some safety concerns with them. I'd avoid them and rent actual ARRI daylight lamps when needed.

[Mark Kenfield]

I've had to use a few over the years. Most have run fine on mains power, but I've had some absolute nightmares on night shoots where producers have rented them to save a buck, and the lamps have simply refused to strike from portable gennies.

 

Build quality can also be an issue with dodgy barndoors and yokes that won't lock in place properly.

 

I'd strongly suggest sticking to the old reliables when it comes to HMIs.

[Aapo Lettinen]

Yeah build quality may be a serious issue and may also cause safety concerns. I bought some as arri tungsten fresnels last year for testing them out and for personal projects and had to repair them all at first to be able to use them. The materials may not necessarily be an issue but the quality control and quality of workmanship is. There was faulty bulb bases, loose strain reliefs, scratches on completely new lights, bad quality bulbs (may be very dangerouas with hmi lights!) , bad quality power cords (the rubber is starting to degrade after one year of very light use and I have to replace them soon). They saved some serious money compared to arri yes but they would have been very dangerous to use out of the box and actually only one of the three lighta even worked out of the box, had to repair them all

[JD Hartman]

Don't own but have seen first hand the counterfeit ARRI Fresnel lights. Owner/operators all had similar comments: didn't work; bad wiring; poor fit and finish; literally shocking. Still a bargain after you put better quality parts and your time into them? I don't see how.

 

I don't anyone with a far east HMI, but I would have to view them as disposable. Who is going to service the ballast when it fails after six months or a year? Who is going to repair your reputation when the light fails on a paid shoot?

Edited December 27, 2015 by JD Hartman

[Phil Rhodes]

Anything can fail. It's easy to sit back, as someone working on high-budget stuff, and decry anything but the best. If it's that or no HMI, I'll take it.

 

P

[JD Hartman]

Anything can fail. It's easy to sit back, as someone working on high-budget stuff, and decry anything but the best. If it's that or no HMI, I'll take it.

 

P

 

That's B.S. Phil. How's that far east ballast you have doing? The one you were unable to get even the head cable pin-out for?? Maybe you can post 3, 6 and 12 months usage (in hours) and durability reports. It has nothing to do with high-end shoots, it's safety foremost and reliability.

While I'd rather die with my boots on than die in bed, I don't want to be electrocuted on set either.

Edited December 27, 2015 by JD Hartman

[Mark Dunn]

I think Phil is referring mainly to his own use. He and I would be happy to handle our own mains wiring but probably wouldn't sell or rent it, and of course we are dealing with the more dangerous 240V.

I know how not to get a shock but it happens when working on a circuit. I wouldn't expect to get one in service, and my cable grips are so tight you can pull the plug out of the socket.

[Phil Rhodes]

I'm not here to defend anything, but the ballast I have is actually exactly the same one that GAM supply with their 575 HMI profiles, so I don't think there's any real issue with it beyond its being permanently, in effect, in flicker free mode. This creates acoustic noise problems, and I'm not particularly happy with it. I'm looking to replace it, but that's sort of the problem - there's nothing better for less than ten times the money and get this - UK manufacturers won't even return my phone calls. The Chinese we actually more helpful than the locals. It's genuinely astonishing.

 

The other thing to be aware of is that at least one major manufacturer of LED lighting, a manufacturer perceived as high-end, has been supplying revoltingly-bad power supplies for years and everyone seems to accept it as normal. Paying someone a lot of money to stamp their insignia over the "made in china" logo, sadly, is not a reliable way to keep manufacturers honest.

 

So, for all these reasons, quality is good. Reliability is good. But elitism is idiocy.

 

There is a fine line between insisting on quality and being elitist. That line moves around, depending on the situation. Pretending that the way you do something is the only way to do something is, if nothing else, fundamentally factually incorrect, but also desperately misleading. I maintain that if it's a choice between a Chinese HMI and none, I'll take the light. If it breaks, I'm only back where I started.

 

Oh, and Mark, no, I wouldn't sell it. I occasionally lend it out to people I know and in whose competence I trust. But honestly, who doesn't take that approach?

 

P

[Mark Dunn]

 

Oh, and Mark, no, I wouldn't sell it. I occasionally lend it out to people I know and in whose competence I trust. But honestly, who doesn't take that approach?

 

P

Probably not a policy you could rely on in the sort of jurisdiction where if you slip off a wet ladder you sue 1) the person who sold you the ladder, 2)the maker of the ladder and probably 3) God, for raining on it.

I've done electrical things to the Steenbeck but nothing you could fry yourself on and if someone lost a finger in the sprocket, well, at least I didn't design it and I don't have to remember to tell them not to stick their fingers in it. I've replaced the fan and dusted it so this won't happen.

[JD Hartman]

I'm not here to defend anything, but the ballast I have is actually exactly the same one that GAM supply with their 575 HMI profiles, so I don't think there's any real issue with it beyond its being permanently, in effect, in flicker free mode. This creates acoustic noise problems, and I'm not particularly happy with it. I'm looking to replace it, but that's sort of the problem - there's nothing better for less than ten times the money and get this - UK manufacturers won't even return my phone calls. The Chinese we actually more helpful than the locals. It's genuinely astonishing.

 

The other thing to be aware of is that at least one major manufacturer of LED lighting, a manufacturer perceived as high-end, has been supplying revoltingly-bad power supplies for years and everyone seems to accept it as normal. Paying someone a lot of money to stamp their insignia over the "made in china" logo, sadly, is not a reliable way to keep manufacturers honest.

 

So, for all these reasons, quality is good. Reliability is good. But elitism is idiocy.

 

There is a fine line between insisting on quality and being elitist. That line moves around, depending on the situation. Pretending that the way you do something is the only way to do something is, if nothing else, fundamentally factually incorrect, but also desperately misleading. I maintain that if it's a choice between a Chinese HMI and none, I'll take the light. If it breaks, I'm only back where I started.

 

Oh, and Mark, no, I wouldn't sell it. I occasionally lend it out to people I know and in whose competence I trust. But honestly, who doesn't take that approach?

 

P

 

It's a known fact that the Chinese build and export to meet a price point. So while they may look the same, I refuse to believe that the component selection and build quality are the same for the Fleabay and direct sales HMIs ballasts as those built to be sold under a "name brand" label. You can observe the same thing in Chinese manufactured portable power tools, those sold by Princess Auto, Canadian Tire, Horrible Freight, Hare and Forbes, etc. may look the same as the ones branded Milwaukee, but the reliability and performance are vastly different.

 

HMI(s)? Rent them. Why own and maintain something that is used infrequently? You're not shooting your own projects daily or even weekly are you?

 

It's not an elitist view, all this counterfeit ARRI (and Strand, Ianario, etc.) equipment should be intercepted and crushed right at the dock. Last time I looked, ARRI heads and ballasts were still being made in Germany.

 

When you ballast goes T.U., you can't fix and no one will touch it, your not just back at the beginning, you are xxx pounds or Euros behind the eight ball.

[Phil Rhodes]

It's a known fact that the Chinese build and export to meet a price point. So while they may look the same, I refuse to believe that the component selection and build quality are the same for the Fleabay and direct sales HMIs ballasts as those built to be sold under a "name brand" label.

 

Nobody's arguing.

 

 

 

Why own and maintain something that is used infrequently?

 

This is a really common argument and there are a lot of very good counterpoints. You might not live near a rental facility. You might not often have an easy way to insure a rental. The cost of going to pick it up, in time and transport, can approach or exceed the cost of the rental itself. You may need it at short notice. This is a common suggestion from people who work on big productions, to whom the addition of one 575W HMI to a rental package is pretty trivial. If the 575W HMI is the entire order, it's a bit of a different story.

 

And actually many people do need to be shooting more than weekly!

 

all this counterfeit ARRI (and Strand, Ianario, etc.) equipment should be intercepted and crushed right at the dock.

 

Again, I'm not really arguing. Deliberate copying of other people's products should be enforced a lot better than it is, although really all that would do is force people not to paint it blue. I have written whole articles about genuinely dangerous imports which should certainly be stopped at the border. There are some very dangerous situations arising with poor-quality lithium-ion cells and battery chargers which are causing problems commonly enough to make the mass media.

 

I'm actually rather less confident in the as-Arri fakes than the one I got, which at least is an original design and not deliberately built to imitate someone else's product.

 

 

 

When you ballast goes T.U., you can't fix and no one will touch it, your not just back at the beginning, you are xxx pounds or Euros behind the eight ball.

 

Well, you could say the same about any of those GAM owners, but that's not the point.

 

The point is, do you have any idea how many of these things I can buy for the cost of an Arri 575 ballast? The literal answer is more than nine. Even taking into account the fact that you're actually buying the 575/1200 combo, there's a limit to how bad it can possibly be (the 400/575 is often more expensive, for some reason). I can have two spares sitting in the car, and it's still three times cheaper. There is an LTM ballast that's a bit cheaper, which I suspect is exactly the same guts and you're paying $1k for the Arri logo, but it doesn't make that much odds. That's the problem. I don't particularly like it any more than you do, but the economics of the situation are impossible to ignore if you're the one paying for it.

 

Oh, and - the UK government just awarded a contract to build nuclear power plants to a Chinese company. Yes. I know. I know. Order your lead-lined underwear now.

 

P

[JD Hartman]

Why own and maintain something that is used infrequently?

 

Phil said, "This is a really common argument and there are a lot of very good counterpoints. You might not live near a rental facility. You might not often have an easy way to insure a rental. The cost of going to pick it up, in time and transport, can approach or exceed the cost of the rental itself. You may need it at short notice."

 

Phil, like it or not, you are the case study here. Do you live away from civilization, can you apply for L&D insurance for a one or two day shoot online and get immediate coverage? Rental house verifies via a phone call.

 

 

 

The real deal:

http://www.ebay.co.uk/itm/Arri-Daylight-Compact-575-HMI-Fresnel-with-575w-1200w-Arri-Ballast-Cable-/252225958041?hash=item3ab9d6b099:g:qUMAAOSwhkRWfc-E

 

The counterfeit:

http://www.ebay.co.uk/itm/Flicker-free-100-575W-HMI-Fresnel-Light-Ballast-OSRAM-Bulb-For-Film-Video-/331553593417?hash=item4d32225849:g:kncAAOSw7aBVJcQ6

 

True both are Fresnels, but they are just an example.

 

Buy quality and it only hurts once.

[Phil Rhodes]

Do you live away from civilization, can you apply for L&D insurance for a one or two day shoot online and get immediate coverage? Rental house verifies via a phone call.

 

I can and occasionally do, although a basic production insurance package is worth many times what the rental of that 575 would be. That's the problem. It would also be a couple of hours to go pick it up and drop it off, so that's an entire day I can't book either side of the job to collect and return, and many places will, not unreasonably, charge those half days as rental. So, that 575 you had thrown on the truck for a heavily discounted rate well under $100 ends up costing me hundreds.

 

As I say, if you're on a big show and you already have insurance and a truck coming down, and you need one more item - that's one thing. If you need a very limited amount of stuff for one day, as one often does on small shows, that's quite another. You don't have to be very far from a rental facility for it to be impractical to pick up and drop off on the same day it's used. Many productions don't need or have insurance beyond the public and employers' liability that most people have as a matter of course. I no longer own any gear I insure for loss or damage.

 

As to buying quality - again, nobody's arguing with you. At some point, though, it's a business decision. Will someone pay you $100 a day for a 575W HMI, ten days a month? If so, you buy one. If not, you don't. If you still need something anyway, you get something cheaper. It's a very straightforward, economically-motivated business decision. I had exactly this conversation with someone from Fuji about their 19-90 zoom. Could I go out and get a loan to buy one? Of course. But it'd just be a daft thing to do. There is no value judgment intrinsic to this. It's not about what I think of a product. The Cabrio is a beautiful lens. It's about does it makes sense, and if it doesn't, you don't do it. I'm not sure what's controversial here.

 

P

[Alexandre de Tolan]

 

Last time I looked, ARRI heads and ballasts were still being made in Germany.

 

Not quite! ARRI signed a contract with Danish Brother Brother and Sons for all their LED ballast fixtures and they are done outside Germany for some time now. Not saying that BBS isn't a high standard company, which it is, but nonetheless made outside Germany and ARRI themselves.

 

As for the "subject matter" of this thread I have to say that I'm with Phil here. Everything is prone to failure. Yes, some things more than others but just for the sake of an argument, last year I was operating in a feature shot in a remote Guiné Bissau location and all (and I mean all), the Jokers we've had have fried in the first day of shooting. The DP went to light the whole film on cheap Indian LED fixtures, and they worked!

Edited December 28, 2015 by Alexandre de Tolan

[JD Hartman]

 

Not quite! ARRI signed a contract with Danish Brother Brother and Sons for all their LED ballast fixtures and they are done outside Germany for some time now. Not saying that BBS isn't a high standard company, which it is, but nonetheless made outside Germany and ARRI themselves.

 

As for the "subject matter" of this thread I have to say that I'm with Phil here. Everything is prone to failure. Yes, some things more than others but just for the sake of an argument, last year I was operating in a feature shot in a remote Guiné Bissau location and all (and I mean all), the Jokers we've had have fried in the first day of shooting. The DP went to light the whole film on cheap Indian LED fixtures, and they worked!

 

Okay, we're splitting hairs here, I was referring to HMI ballasts....

LEDs have regulated power supplies, not ballasts.

The Joker ballasts failed because of what? Poor quality/dirty power supplied by an (insufficiently sized?) generator?

[Alexandre de Tolan]

 

The Joker ballasts failed because of what? Poor quality/dirty power supplied by an (insufficiently sized?) generator?

 

Yes. You're right. Nonetheless it was the only one [generator] that the Gaffer could put his hands on at the "end of the world" where populations don't know what the word electricity means. At the end of the day were the cheap knock off lights that have put the film together.

[Phil Rhodes]

Not to crow, but I would have to point out that building what's essentially a switching power supply with a sufficiently fragile front end that a bad generator could destroy it is not a particularly good advertisement for the high end. The fact that people continue to supply devices for film and TV use, knowing that they may be used in large numbers, without power factor correction is another problem. The point of paying the big money would ordinarily be that one would expect to get these special features because it's a special purpose device. The fact that we don't is very disappointing.

 

But I digress. Interestingly enough, a modern electronic HMI ballast and the low-voltage power supplies typical of LED lights have more in common than might be obvious at first glance. Both are switching power supplies. Modern HMI ballasts effectively work by rectifying the incoming mains and chopping the DC results into a square wave at a few hundred or a few thousand cycles per second; the main difference is that the HMI is a current-mode or total-wattage regulated device with special provision for a high open-circuit voltage to facilitate starting, whereas the external power supplies for LEDs are just voltage regulators (the current regulators for the LEDs are generally built into the lights).

 

They're both switch-mode power supplies and they both have similar concerns as regards input filtering, power factor, and their reaction to dirty mains.

 

P

[JD Hartman]

We call them ballasts, because (as much as some will argue otherwise) they (magnetic HMI ballasts) were derived from HID lighting ballasts, metal halide, high pressure sodium, etc.

[Phil Rhodes]

The etymology is actually quite interesting. It comes from the idea of putting weight in the bottom of a ship to stabilise it. Strictly speaking, an LED driver is also a ballast, inasmuch as it regulate the otherwise-unstable flow of current.

[Guy Holt]

I've had to use a few over the years. Most have run fine on mains power, but I've had some absolute nightmares on night shoots where producers have rented them to save a buck, and the lamps have simply refused to strike from portable gennies.

 

I haven’t had personal experience with the Chinese Arri knock-offs, but a HMI service tech told be recently that part of the reason that they are so inexpensive is that they are not power factor corrected, which would account for why Mark had difficulty operating them on portable generators but not on wall power. The harmonic currents drawn by non-pfc ballasts interact with the high impedance of portable generators to create voltage waveform distortion that can cause the HMIs to not strike.

 

Put simply, when you plug a non-pfc ballast into a wall outlet you need not be concerned about harmonic currents. The impedance of the electrical path from the power plant is so low, the distortion of the original voltage waveform so small (1-3%), and the plant capacity so large in comparison to the load of the one light, that the inherently noisy load of non-pfc HMI ballast will not affect the voltage at the distribution bus.

Left: Grid Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Right: Conventional AVR Power w/ 1.2Kw Arri non-PFC Elec. Ballast.

 

It is, however, an all together different situation when plugging non-pfc HMI fixtures into conventional portable generators. As a comparison of the oscilloscope shots above indicate, the harmonic currents drawn by non-pfc ballasts can generate voltage distortion in the power stream. Given the large sub-transient impedance of conventional portable generators, and the fact that the original supply voltage waveform of conventional generators is appreciably distorted (a THD of 17-19%) to begin with, you have a situation where the return of any harmonic currents by a non-PFC electronic ballast (HMI or Kino) will result in significant waveform distortion of the voltage in the distribution system.

 

The adverse effects of the severe harmonic noise exhibited above left, can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral return, and instability of the generator’s voltage and frequency. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference. In other words, saving a few bucks by buying Chinese knock-offs can cost you a considerable amount of money in lost time or damaged equipment. For a detailed explanation for why this is, use this link for my article on the use of portable generators in motion picture production.

 

 

This article is cited in the 4th Edition of Harry Box's "Set Lighting Technician's Handbook." Of the article Harry Box exclaims:

“Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."

 

The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

 

 

- Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston

[Evan Bourcier]

Appreciate everyones feedback! Definitely some interesting thoughts shared here, and I definitely see both sides of the coin. I do actually shoot my own projects a lot, so it's beneficial for me to have my own kit. I'm also a couple hours from the nearest rental house. I didn't realize actual Arri HMIs could be had as cheap as shared above, I've mostly seen joker prices. Why is an Arri 1200 watt HMI par $1800 while an 800 watt joker is $6500 on eBay? I'm sure there's some basic thing I'm missing here, as I've shot with jokers but never the Arri.

 

 

I haven’t had personal experience with the Chinese Arri knock-offs, but a HMI service tech told be recently that part of the reason that they are so inexpensive is that they are not power factor corrected, which would account for why Mark had difficulty operating them on portable generators but not on wall power. The harmonic currents drawn by non-pfc ballasts interact with the high impedance of portable generators to create voltage waveform distortion that can cause the HMIs to not strike.

 

Put simply, when you plug a non-pfc ballast into a wall outlet you need not be concerned about harmonic currents. The impedance of the electrical path from the power plant is so low, the distortion of the original voltage waveform so small (1-3%), and the plant capacity so large in comparison to the load of the one light, that the inherently noisy load of non-pfc HMI ballast will not affect the voltage at the distribution bus.

Left: Grid Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Right: Conventional AVR Power w/ 1.2Kw Arri non-PFC Elec. Ballast.

 

It is, however, an all together different situation when plugging non-pfc HMI fixtures into conventional portable generators. As a comparison of the oscilloscope shots above indicate, the harmonic currents drawn by non-pfc ballasts can generate voltage distortion in the power stream. Given the large sub-transient impedance of conventional portable generators, and the fact that the original supply voltage waveform of conventional generators is appreciably distorted (a THD of 17-19%) to begin with, you have a situation where the return of any harmonic currents by a non-PFC electronic ballast (HMI or Kino) will result in significant waveform distortion of the voltage in the distribution system.

 

The adverse effects of the severe harmonic noise exhibited above left, can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral return, and instability of the generator’s voltage and frequency. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference. In other words, saving a few bucks by buying Chinese knock-offs can cost you a considerable amount of money in lost time or damaged equipment. For a detailed explanation for why this is, use this link for my article on the use of portable generators in motion picture production.

 

 

This article is cited in the 4th Edition of Harry Box's "Set Lighting Technician's Handbook." Of the article Harry Box exclaims:

“Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."

 

The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

 

 

- Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston

This info is really interesting Guy - so if I'm reading correctly you think these should be relatively safe on house power? Most of my non-travel jobs are house power, so I'd be willing to accept that as a limitation.

Also - saw you're in Boston, I'm actually based out of Springfield MA! Would love to connect some time, I've been working here for 4 years but know very little of the Boston scene. (And I could always use a good Gaffer!)

[Colin Elves_18850]

I've got a Chinese 1.2K HMI. It works fine. I ran it off an equally cheap 2.8kw petrol generator and, again, it worked fine. As Phil says it does seem to be permanently stuck in flicker free mode (240fps flicker free, if anyone is wondering) despite having a knob on the front to supposedly change modes (thanks for clarifying that Phil, I thought I was going mad!) so it is indeed very noisy: the head buzzes loudly and the ballast has a huge noisy fan inside, so not so great for narrative...

 

Build quality is utter shite, although I'm confident the lens is proper as no one has got horrible sunburn from it so far: the focussing screw is sticky as hell so I suspect it will just get stuck eventually and the stand nut is always wobbly (a tad worrying) but hey, as Phil says it's really really **(obscenity removed)** cheap. I bought the damn thing for the cost of 4 days hire - including a stand and I've already used it for more than 4 days. To be honest. I hope they bring out a 2.5K version as that's one of the lights I'm missing from the 'low budget feature' kit I'm trying to put together.

[Guy Holt]

This info is really interesting Guy - so if I'm reading correctly you think these should be relatively safe on house power? Most of my non-travel jobs are house power, so I'd be willing to accept that as a limitation.

 

Even if you only plan to use house power, you may want to consider getting a power factor corrected ballast. Without power factor correction the 1200W Chinese Arri knock-off will surely trip a 15A circuit and maybe even trip a 20A circuit. The reason for this is that non-PFC HMI ballasts draw current in high amplitude pulses that include harmonic currents. I won’t go into detail here on the adverse effects that the harmonics generated by non-PFC electronic HMI ballasts can have, but anyone operating HMIs, Kinos, and even LEDs should make themselves acquainted with harmonics (use this link for more details.)

 

Since Ohm's law (W=VxA) doesn't apply to HMI ballasts, the only way to know how much current a HMI ballast will draw is to read the manufacturer’s nameplate. Let’s take a look at one of these nameplates, since deciphering them can be as difficult as deciphering Egyptian Hieroglyphs if you don’t know how to read them.

 

Manufacturer’s nameplate from an Arri 575/1200 Electronic Ballast specifying its’ electrical characteristics (learn how to read it.)

 

Above is the nameplate from an Arri non-PFC 575/1200 Electronic Ballast. The first thing to look for is the ballast’s Volt-Amperes (VA), which is called “Pmax” here. Calculated as the RMS voltage times the current measured at the input to the device, Volt-Amperes is the measurement of "Apparent Power" delivered to a load, which is different than Wattage. Wattage is the True Power dissipation of the lamp calculated by integrating the product of current through the lamp and voltage over time. These may sound like they would be the same (they are in the case of incandescent lamps), however one characteristics of HMI, Flourescent, and LED power supplies is that some of the current flowing into them is not used in the generation of light. The relationship between True and Apparent Power is called the Power Factor (PF.) Since, the Wattage will always be lower than or equal to the Volt-Amperes, PF varies from 0.0 to 1.0.

 

As indicated on its’ nameplate, this ballast has an Apparent Power of 2290VA - which means it draws nearly twice the load of its’ 1200W output. Next to the Pmax, it also indicates that the Power Factor is .6 (cos@=.6) meaning the ballast has to draw 40 percent more power than it uses to generate lumens. The greater Apparent Power drawn by the ballast consists not only of high amplitude short pulses of current, but also harmonic currents that the ballast also draws.

 

The next thing to look for is the relationship between Voltage (U) and Current (I). As this nameplate indicates this ballast will operate with line voltages ranging from 90 to 125 volts (US), and 180 to 250 volts (European.) You will also notice that the current (I) the ballast draws varies with the supply voltage. That is because this ballast is a “Constant Power” ballast. With constant power ballasts, if voltage drops the ballast will draw more current to maintain a constant Apparent Power - 2290VA in this case. For example, according to the nameplate it will draw 18A of current (I) at 125 Volts (U) (2290VA/125V = 18.32A.) If the voltage drops to 90V, it will draw over 25 Amps (2290VA/90V = 25.44A.)

 

This is an important characteristic of non-pfc HMI ballasts that should be taken into account when used outside the studio on location. With an Apparent Power of 2290VA, this non-PFC constant power HMI ballast will operate very close to the threshold of a 20A circuit – too close to operate reliably unless precautions are taken. For example, according to its’ nameplate, it takes 19 Amps at 120 Volts to generate 1200 Watts of light (2290W/120V = 19A). If there is any line loss from a long cable run, the ballast will possibly draw over 20 Amps in order to compensate for the voltage drop. For instance, at 110V it will draw 20.8 Amps. To the problem of line loss, usually there is also increased resistance from an overheated plug end, which makes the voltage drop even further. Since most stinger plug-ends are only rated for 15 Amps they tend to overheat with 1200W non-PFC electronic ballasts. The increased resistance that results from the heat causes the voltage to the ballast to drop even further and so it will draw more power to maintain the 2290VA load. If the light is operating on a small generator, there will also be voltage drop on the generator because of the greater load. The voltage output of generators can drop 5-10 volts under load. At 105V, the ballst that drew 19A at 120V, will now draw 21.8 Amps and cause circuit breakers to overheat and potentially trip.

 

Guy Holt, Gaffer,

SceenLight & Grip,

Lighting Rental & Sales in Boston

[Phil Rhodes]

. As Phil says it does seem to be permanently stuck in flicker free mode (240fps flicker free, if anyone is wondering) despite having a knob on the front to supposedly change modes

 

 

The one I have is not any sort of attempt at an Arri clone. It doesn't even have the switch:

 

 

I'm told that putting a real Osram bulb in them can help, although an Osram 1200W HMI is not a terribly cheap object - and mine is a real Osram bulb, and it still buzzes. It gets a lot quieter once it's warmed up, as per usual. If the character of the buzz on yours doesn't change when you alter the mode switching, I'd be a bit suspicious that it may just be a knob. And some LEDs.

 

It's probably possible to replace the fan in the ballast with a quieter one. I did.

 

I'd buy a "real" one, but honestly, they're not a couple of times more expensive, they're ten times more expensive.

 

And I'm not expecting to get any sort of rental for it. Who understands that lights are worth paying for, in London...

 

P