Manual or schematic for old Arri HMI ballast

JD Hartman · May 5, 2007

Looking for information on an old magnetic ballast I picked up. I contacted ARRI at their repair center, but they won't provide any information. It is a 1.2kw, marked type B1.2

Frank Barrera · May 5, 2007

Looking for information on an old magnetic ballast I picked up. I contacted ARRI at their repair center, but they won't provide any information. It is a 1.2kw, marked type B1.2

Your best bet is to call up your friendly nieghborhood rental house. they may have it becasue they have to fix them. try the lighthouse in Jersey 800.721.6191.

good luck

Edited May 5, 2007 by Frank Barrera

May 11, 2007

for a general idea of what is going on check out this page

http://www.lightlineelectronics.com/HMI.html

and to get they specific one you want, go here

they have some online here right now...

http://galaxyrepairservice.com/whats_new.html

but he said that he would help with whatever schematic you needed...

email me a copy when your done if any of these help..

thanks,

david

JD Hartman · May 11, 2007

Thanks for all the suggestions. I was just at Lighthouse yesterday and used the opportunity to look over their ballasts. Didn't see one that matched this boat anchor and I didn't have the time to ask if they had one stuck off in a corner.

Angel Ovalles · March 9, 2015

Do you know if its an magnetic or electronic ballast? what color is it? I am an ex-ARRI hmi ballast repair technician and might be able to help.

Edited March 9, 2015 by Angel Ovalles

Guy Holt · March 11, 2015

Looking for information on an old magnetic ballast I picked up. I contacted ARRI at their repair center, but they won't provide any information. It is a 1.2kw, marked type B1.2

There are several things you need to know about the Arri magnetic ballasts and you won’t find them in a manaul. First, they were made by Irem and marketed by Arri which means the Irem schematics on Galaxy’s website would be applicable. Also, magnetic ballasts in general are not forgiving when it comes to flicker. The problem with them is that the light intensity of a HMI powered by a magnetic ballast follows the waveform of the supply power and increases gradually until it peaks and then decreases. Since there are two peaks per cycle (+ & - ), the light pulses twice every AC cycle or 120 times a second (see illustration below. ) This fluctuation in the light output is not visible to the eye but will be captured on film or video if the frequency (Hz) of the AC power is not precisely synchronized with the film frame rate or video scan rate. If the AC Frequency of the power were to vary, a frame of film or video scan, would receive more or less exposure depending upon the exact correspondence of the film/video exposure interval to the cycling power waveform because the light intensity is pulsating at twice the AC frequency.  

The sinusoidal 60Hz current of a magnetic ballast (left) creates a pulsating light output (right)

Electronic square wave ballasts eliminate the potential for flicker by squaring off the curves of the AC sine wave supplying the globe. Squared off, the changeover period between cycles is so brief that the light no longer pulsates but is virtually continuous (see illustration below.) Even if the AC Frequency of the power were to vary, a frame of film or video scan, would receive the same exposure because the light intensity is now not pulsating but nearly constant. In other words, electronic ballasts are “flicker free” because they square off the power sine wave which causes an increase in the duration of the peak level of light output so that the light is on more than it is off. Electronic HMI ballasts are also called “square wave” ballasts for this reason. The down side to electronic HMI ballasts is that because of their sophisticated electronics they are more expensive and more fragile than magnetic ballasts, and if they are not power factor corrected, they will draw more current than a magnetic ballast.

The refined square-wave signal of an electronic ballast (left) creates virtually even light output (right)

(Illustrations courtesy of Harry Box)

Magnetic ballasts will operate reliably on the Honda EU series generators because Honda's sine-wave inverter technology provides much higher quality power than conventional (non-inverter) generators. With a waveform distortion factor of less than 2.5%, the power generated by Honda’s EU series of generators is quite often better than what you get out of the Crawford Studio Units. The power these machines generate is rock solid with a frequency variance of only hundredths of a cycle - which eliminates the need for costly crystal governors. The Honda EU series generators provide true sine wave power with enough frequency stability to power HMI's with magnetic ballasts without flicker at certain safe frame rates and shutters. As long as you shoot at one of the many safe frame rates, magnetic ballasts are “flicker free” with the Honda inverter generators.

Depending on the type of filming you do, you may in fact be better served by an older magnetic ballast over a non- Power Factor Corrected electronic ballast. A non-pfc 1.2kw electronic ballast draws 19amps (verses the 13.5 amps of a magnetic ballast) so it will always trip the common 15amp house circuit and will trip a 20 Amp circuit if there is something else, like a computer or light, on the same circuit. Where you can't always know what else is on the same circuit, or even if it is a 20 or 15 Amp ciruit, a 1.2kw magnetic ballast drawing only 13.5 Amps is the safer bet since it can operate on a 15 amp circuit even with other things on the circuit. Non-Power Factor Corrected electronic ballasts are meant to be used on film sets where every circuit is 20 Amps and you know what is on the circuit because you are distributing the power yourself from a tie in or generator. If your style of shooting requires that you plug into wall outlets, you will be better served by a magnetic ballast.

But that is not the only benefit to using a magnetic ballast over a non-PFC electronic ballasts. If you don’t have access to the newest PFC electronic ballasts, the older magnetic ballasts are in fact cleaner running on portable gas generators than non-PFC electronic ballasts. That is because the harmonic distortion created by non-PFC ballasts reacting poorly with the distorted power waveform of conventional AVR generators limited the number of HMIs you could power on a portable generator. The primary factors limiting the use of HMIs on portable generators has been the inefficient use of power by non-PFC electronic ballasts and the harmonic noise they throw back into the power stream. The adverse effects of this harmonic noise (evident in the oscilloscope shots below), can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral wire, and instability of the generator’s voltage and frequency. For these reasons it has never been possible to operate more than a couple of 1200W HMIs on a conventional 6500W portable gas generator.

As is evident in the oscilloscope shots below of a 1200W magnetic HMI ballasts on grid power (left), on power generated by a conventional AVR generator (middle), and power generated by an inverter generator (right), the lagging power factor caused by the inductive reactance of magnetic ballasts has by comparison only a moderately adverse effect on the power waveform. Outside of causing a voltage spike in the inverter power, magnetic ballasts actually show a positive effect on the already distorted power waveform of the Honda EX5500 conventional generator. For this reason magnetic ballasts work better on conventional generators with frequency governors than do non-PFC electronic square wave HMI ballasts.

These oscilloscope shots show that if you don’t have access to the newest PFC electronic ballasts, the older magnetic ballasts are in fact cleaner running on portable gas generators than non-PFC electronic ballasts. And, where inverter generators like the Honda EU6500is do not require crystal governors to run at precisely 60Hz, you can operate magnetic HMI ballasts reliably on them. In addition, the smaller magnetic ballasts (575-2500W) offer the distinct advantage of being less expensive and draw less power (once they have come up to speed) than the commonly available non-PFC electronic equivalents (13.5A versus 19A for a 1.2kw.)

Of course there are downsides to using magnetic ballasts. One down side is that you are restricted to using only the safe frame rates and shutter angles. But, when you consider that every film made up to the early 1990s were made with magnetic HMI ballasts you can see that being limited to the safe frame rates is not all that restrictive. Another downside to magnetic ballasts is that you can’t load the generator to full capacity because you must leave “head room” for their higher front-end striking load. When choosing HMIs to run off portable generators, bear in mind that magnetic ballasts draw more current during the striking phase and then they “settle down” and require less power to maintain the HMI Arc. By contrast, an electronic ballasts “ramps up”. That is, its’ current draw gradually builds until it “tops off.”

If it sounds like I’m hyping the Honda EU6500is generator, it is not because I rent or sell them. As a Gaffer of a lot of tight budgeted independent shorts, I think these machines are a major development in portable power. Since magnetic HMI ballasts will operate flicker free at all standard frame rates on them (without the need for a crystal governor), inverter generators like the Honda EU6500is give new production life to older 2.5kw & 4kw HMIs with 120V magnetic ballasts. And now that you can parallel two of them for 120A output, they give new life to 6 & 12kw HMIs as well.

For more detailed information on using magnetic HMI ballasts on Honda portable generators, I would suggest you read a white paper I wrote on the use of portable generators in motion picture production that will be available soon as an e-book from the Academy of Production Technology Press (APT.)

Harry Box, author of The Set Lighting Technician’s Handbook has cited my article in the just released 4th Edition of Harry Box's “Set Lighting Technician's Handbook” (http://www.screenlightandgrip.com/html/BoxBook.html) and featured on the companion website “Box Book Extras." 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 original white paper is still available online for free at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

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