Film-Tech Forum ARCHIVE: More light? Is it possible?

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Posted by Tim Sherman (Member # 569) on 12-12-2000, 04:43 AM:

Well story goes i have a drive-in movie theater with a pretty large screen (118'x 50') right now i am running an orc 6000 lamphouse with a 5,000 watt xenon, a simplex 35 projector, and a brand new schneider reverse anamorphic and back-up. im running a regular speed intermittant. i would love to get more light to the screen. i am thinking of first upgrading to a 6,000 watt xenon and running both water and air cooling on the projector. how do you think this will work and is there anything else you think i should do to prepare for the change. i have thought of a high speed intermittant, but i know they are expensive and or hard to find. and i have heard very hard to make it reliable in the machine. is there anything else that i can do to get more light out of this machine? any help would be greatly appreciated.

Come on out to the drive-in and spend a night out with the stars

Posted by Jerry Chase (Member # 660) on 12-12-2000, 07:11 AM:

I'm thinking that you might want to investigate a company called Protolite. I haven't seen mention of them in recent years, but they used to advertise a "Mirror Image" silver lenticular screen as a drive-in containment screen. The combo of lenticular and silver allowed them to get a _4.0_ gain screen across a standard DI field. The last address I have for them is 985 Timothy Drive, San Jose CA 95133 ph 408-971-9700.

I have a little sample of their screen material. It can best be described as a very fine corduroy/canvas with a silver plastic overcoat. The stuff really works, AND increases the contrast, giving a better picture, because it rejects most of the ambient light, but could be pricey when covering a screen of that size. Still, the cost of a few 6KW lamps ain't cheap either, and this would be a lot easier on film and result in fewer burned fingers.

While you're spending... Gratuities gladly accepted.

Posted by Ken Layton (Member # 133) on 12-12-2000, 08:02 AM:

Try a Century DAW projector. With it's two counter-rotating shutter blades, it should give you more light. It also has water cooling.

Posted by Stefan Scholz (Member # 147) on 12-12-2000, 11:58 AM:

Forget theidea of a bigger lamp. It is not worth the try. Some figures according to a Bauer sales leaflet from 1979:

Lumen output of Bauer U 3 projector with single bladed 2880 rpm shutter (standard projector, not the drive in gear/ shutter type)
Horizontal Xenons, 35 mm film (1:1.17 window)
1600 Watts 10500 lumens
2500 Watts 13000 lumens
4000 Watts 14000 lumens.

7kW for 70 mm projection only. Will harm 35 mm even with air cooling of film. (Same statements from Strong's Super Lumex brochure.)

Output 70 mm with 4 kW: 22000 lumens.

It seems the maximum light output vs. lamp energy is around 2 kW.
The only way to get brighter images is the use of bigger film formats (no longer possible) or better transport to steady state relations, by use of specific "Drive In" projector gears.
Theese gears used to be more common, when Drive Ins were "bigger business", but still some makers advertise "Open Air" specials.
But maybe someone still has one of those accelerated gear projector mechanisms.
And of course the mentioned higher gain screens, which in turn narrow the usable angle, and which can be somewhat costly.

Posted by Brad Miller (Member # 2) on 12-12-2000, 01:22 PM:

Your problem is with that junker ORC lamphouse. Get rid of it and you will have LOTS more light with another type. Check Christie's SLC line as well as what Strong is putting out these days. ORC lamphouses are light sponges.

Posted by Jerry Chase (Member # 660) on 12-12-2000, 01:33 PM:

This got me curious about the edge falloff and gain of the silver Protolite screen, so I took my sample and stuck it in front of my slide projector to get a subjective view.

Because of the bumps (lenses in very loose terminology) on the screen it is highly direcional in one direction, falling off rapidly if moved more than 15 degrees or so. In the other direction, it is quite forgiving and a decent image can be seen up to maybe a 60 degree angle. Dead on is of course the brightest, but it isn't as glarey bright as one gets from a matte silver screen.

I don't know about a 4 gain, though. Subjectively, the picture looked maybe twice as bright, with little sparkleys in the brighter areas. These sparleys should be minimal once you get further back than a few feet like I was.

A warning, if the screen tower is not properly canted toward the field, this type of screen could be worse than a matte screen.

Reflecting back, (ouch) I've seen less expensive sheet vinyl wallcovering with vertical ridges. I wonder how this would reflect if painted silver?

Posted by John Pytlak (Member # 331) on 12-12-2000, 01:34 PM:

If you can find one in good repair, a 5:1 "drive-in" intermittent will allow you to decrease the shutter blades from about 90-degrees to 72 degrees, giving you significantly more light. They do tend to be noisier, and put more stress on the film perfs, but this should not be a major issue in a drive-in with durable polyester prints. A water-cooled gate is highly recommended for really large lamps, as the film and finger contacting components stay cool.

Keep your screen surface in good repair, and paint it frequently. Someone mentioned using a mix of white and metallic paint to increase gain. If you do use a more "mirror like" surface, you may have a limited viewing angle, or need to curve the screen.

Do all you can to shield the screen from stray lights like signs and streetlights.

Consider the new "red barrel" Isco lenses, which are a new design that allow more light efficiency without significant loss of image quality.

If that ORC lamphouse is the less efficient vertical design, consider going with a more efficient horizontal lamp. You don't really get much more light in going from 6K to 7K.

Be sure your alignment is "on the money", and you are not "hot spotting" the film. Run a loop of a dark scene trailer a few hundred times to be sure you are not causing heat damage to the film. A silver-image black-and-white print would be the most sensitive to heat damage.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Posted by Brad Miller (Member # 2) on 12-12-2000, 01:53 PM:

Which model projectors had drive-in intermittents manufactured at one time for them? Anyone know? Any still being made new?

Posted by David Kilderry (Member # 142) on 12-12-2000, 05:31 PM:

Tim,

A subject close to my heart!

What follows is all tried and tested stuff on a circuit that once boasted 40 drive-ins!

1. You can run 7KW xenons in the right lamphouse. We run 7k with no scorch or hot gate problems in Kinoton lamphouses with water cooled gates and cold light mirrors. The gate is cool to the touch and the curved gate prevents popping. The light is brilliant.

I imagine you can get similar results with Strong and Christie but have the heat shields in place! Today's modern efficient lamphouses leave stuff like the Bauers U3's mentioned in another era. They were good at the time and we used them in many drive-ins.

If you cannot afford an upgrade here, run the correct lamp for your lamphouse and power supply.

Keep mirror correctly aligned and clean, same with the glass heat shield.

2. Use a new lens from Isco or Schneider and keep it clean. If your lens has had drive-in use for over 8 years it is inefficient and costing you light and contrast.

3. Pull the port glass out and run blowers.

4. Use a light efficient projector as mentioned like a Century DAW.

5. Shield the screen from as much extreanous light as possible. Turn external flood lights away if you can, use trees and screening walls to remove all those man-made contrast killers -( term copyright John Pytlak and Kodak).

If each of these gives you 6% more light, you will be 30% better off! That is a minimum from my experience. Most drive-ins have screens too big for today's field sizes and old equipment. The ones that do it right have good light.

We put up with drive-in screens with 2 - 3 footlamberts for too long and the patron cannot always put a finger on why an indoor theatre looks better, but believe me it is one of the main reasons. On a 60 - 80 foot wide drive-in screen having 10 footlamberts is amazing to see. Good luck.

David

Posted by Dave Bird (Member # 490) on 12-12-2000, 07:33 PM:

Kerry Segrave's book talks extensively about the elusive quest for the "containment screen". Actually having a sample of the stuff is kind of rare Jerry, hang onto it. Some companies apparently tried to develop a material that could "plex" your DI on one screen. Perhaps this came by default when they realized that they were getting a very narrow field much like you mention Jerry. So then they thought you could plex by placing your projectors in different areas and letting multiple movies "bounce" off the same screen to specific areas of the theatre!

Interestingly, I heard that recently someone tested a 3M refelective product called Scotchcal. This is used in vinyl signmaking, basically the same as reflective roadsigns. This could easily be applied in rolls to your screen, but I believe you'd have the same problem, too narrow a field. I have a vinyl cutter, but no reflective material right now, or I'd test it.

Posted by Jerry Chase (Member # 660) on 12-12-2000, 08:56 PM:

I've not only got the material, I have the flyer that went along with it. You have to remember that I've been a 3-D nut for more years than most circuits have been in existence.

I suppose that if you used this stuff rotated at 90 degrees, you could "plex" a single screen. Interesting idea, however I feel sure that it was meant to be used with the wide lateral viewing angles and a tight control top to bottom. Side views of many DIs are obscured by trees, but that shot over the back fence can be a killer. I seem to remember nickel coated screens being touted as a containment screen solution at one point.

Scotchcal is a tough clear polyester film (Wait-a-minute! What is running through projectors?) and not a reflective product. Most of the reflective products it protects are made from glass micro beads that are only partially embedded in a paint or plastic. The beads take advantage of internal reflections within the sphere to aim the beam back along the axis of entry. Slick trick, but too directional for a decent movie screen. BTW, reflective beads don't hold polarization, so they don't work for 3-D.

True containment screens would almost have to use the same type of black grid or slats in front of the screen that the pre-lenticular free vision 3-D pictures used.

In any event, a silver screen with proper surface texture will greatly improve light levels. Outdoors, it might need periodic cleaning to maintain an even reflectivity.

Posted by Pat Moore (Member # 380) on 12-12-2000, 10:55 PM:

Always the problem: How to get more energy through a small hole without burning film.

Larger lamps generally produce more energy, but not necessarily more light. Light gain is NOT proportional to wattage.

The ORC lamps you've got are not terribly light efficient. The newer technologies (am I allowed to mention STRONG) and reflectors are much more efficient in getting light through the aperture and into the lens. There's still the energy issue but you might as well do it with 4000W instead of 6 or 7000.

The Simplex Projector probably has an adjustable two-wing shutter on it, so the opening can be increased. Assuming the film can "take the heat", adjust the shutter opening wider in 1/2-inch increments until you see ghosting appear top and bottom on test film. Then close up the opening slightly and you've maximized the efficiency of the projector for those conditions of projection. Again, watch the heat. By opening the shutter, the film is exposed for a longer time to the light energy.

What lenses are you using? Since you've got a Reverse Anamorphic, I assume these are pretty long focal lengths. Lenses can make a difference in light throughput, and the nice thing is they are after the film.

Good luck and keep us advised...

Posted by Dave Bird (Member # 490) on 12-13-2000, 06:13 AM:

Jerry, 3M's "Scotchcal" must be a very generic-type brand, they also use it on the rolls of vinyl for signmaking. I don't know if anyone ever demonstrated a single-screen "plex" or not, I think it was more an "idea" after they figured this stuff wouldn't work. It would be interesting to see the literature. I'll try and get some of the vinyl and see what happens.

Posted by John Pytlak (Member # 331) on 12-13-2000, 07:35 AM:

The 3M retro-reflective material is used for front-screen projection visual effects. A beam-splitter is used to project a background scene onto a retro-reflective screen behind the actors on the set --- the "gain" of the screen is so high (basically a mirror) that it matches the set lighting on the actors.

These materials are much too directional to use as a movie screen in a theatre --- they reflect almost all the light directly back to the projector, and almost none elsewhere.

Posted by John Pytlak (Member # 331) on 12-13-2000, 08:25 AM:

Pat M., Mark G., Gordon M., John E., and others:

Which projectors had optional 5:1 "drive-in" intermittents available? I have seen a rebuilt Simplex intermittent (from Wolk) with the additional linkage to give the faster pulldown, and heard there were others.

Posted by Gordon McLeod (Member # 33) on 12-13-2000, 08:41 AM:

Norelco built a version of the FP7 called the Super7 with a high speed pulldown and a very narrow bladed barrel shutter noisy machine but produced a lot of light

Posted by Jerry Chase (Member # 660) on 12-13-2000, 10:45 AM:

John, you're right. I'd forgotton the 2001 ape scenes where this was used, giving a wierd effect to the tiger's eyes in some shots.

I think they should cover the space station with this stuff, so we can all point our laser pointers at it and make it glow.

Getting totally off-the-wall, does anyone know if the ultimate drive-in was ever tried? By that, I mean finding a place in the middle of nowhere with no light contamination and projecting a full feature film onto the base of a cloud cover.

Posted by John Pytlak (Member # 331) on 12-13-2000, 11:02 AM:

Jerry Chase asked: "does anyone know if the ultimate drive-in was ever tried? By that, I mean finding a place in the
middle of nowhere with no light contamination and projecting a full feature film onto the base of a cloud cover."

When I worked at the Grandview Drive-In, I tried that several times, reflecting the projector beam up with a mirror. But the clouds were always too high and I did not have a lens with the correct (very long) focal length. When the cloud cover was lower, it usually was foggy as well.

It would be kind of neat to develop a projector that could put a movie (or even still) image on low clouds, to use for advertising. I wonder what kind of projector they use to project the bat symbol on the clouds to signal Batman?

Posted by John Pytlak (Member # 331) on 12-13-2000, 11:50 AM:

Jerry --- I recall they also used retroreflective material on the luminous clothing of the residents of the planet Krypton in the opening scenes of "Superman - The Movie". It was a truly "shining" performance by Marlon Brando.

Posted by Dave Bird (Member # 490) on 12-13-2000, 04:23 PM:

Hey, cool, you could lie on your blanket and watch the show! Speaking of "alternative" DI's, anyone ever hear of a ski resort that, once the snowbanks piled high enough in the parking lots, would "cut" a flat white screen with the groomers and have a winter-time drive-in? I've never heard if this was (or is) a continuing thing, or just once or even WHERE they did it. I've talked to some skiers who'd heard of it, but no-one knows where. Anyone know?

John- no light here, I've got projectors, film, damn, no lamps !

Jerry- I found my samples of that 3M Scotchlite reflective stuff. Very directional as well. Wonder if they could make it suitable for film? Certainly the drive-in market wouldn't be enough motivation for a company like 3M, but could such a material allow for better light output at any theatre with smaller lamps???

Posted by John T. Mellor (Member # 468) on 12-13-2000, 09:47 PM:

The problem of getting enough light on a drive in screen will probally go on for quite a while . Fortunatly I used to work the booth at the MT Penn Drive in outside of Reading Pa.We had what I think were the best lamps for the job Perless Model 15 Hycandecent, If you ever ran one you know what I mean . Anyhow, at my drive in till the land was sold [I leased ,didn't own the land] I used Knisley Xenex I lamphouses with glass reflectors 4k lamps at 150 amps simplex XLs and the light was great. I know that Simplex made the high speed intermittents and I may be able to find one or two if you are realy interested. If I can be of any assistance Tim , E- mail me at johnm816@juno.com

regards,
John

Posted by Pat Moore (Member # 380) on 12-14-2000, 08:21 AM:

Nice to be out of airplanes again...for a while, that is.

In our company, Simplex used the only high speed intermittent that I'm aware of. I don't think Century did one, but used the double-shutters to improve light efficiency. We have fooled around with them in Ballantyne but for different purposes and not necessarily light efficiency improvement.

For your big beam projector, Strong makes a "P3 Pattern Profile Projector". This thing can project an image on a mountainside or a building a mile or more away. Take a look at: http://www.xenotechusa.com/html/body_p3.html

Pat

Posted by John Pytlak (Member # 331) on 12-14-2000, 08:28 AM:

Do they have any "Batman" gobos to signal Batman in the clouds?

Posted by Jerry Chase (Member # 660) on 12-14-2000, 09:03 AM:

Dave, IIRC, they make the reflective beading for this stuff by spritzing hot glass into the air, where it solidifies in the form of tiny spheres. That makes the spheres inexpensive, and it is only a matter of sizing and binding them to complete the product. Getting a wider angle of reflectance isn't possible with this technique, which is why some "lenticular" screens have used "silver" paint molded into various bumps and valleys.

If you want to play around, you can get bottles of the larger glass spheres. They are sold as an additive for reflective parking lot paint. Long before the nice reflective car finishes commonly available today, I added some of these to an overcoat paint job on a hot car I had. The surface was bumpy as hell, (almost like sandpaper)but it did reflect, kinda like today's license plates.

I guess micro-etching techniques could create a roller/mold for a super high gain directional screen, which could then be surfaced with a thin layer of chrome, but I think the costs would be outa sight, and the angles would have to be tailored to whether the surface was going to be screen right, screen left, or center. Otherwise light fall off at the edges and hot spots could be a problem, depending on your viewing position.

Posted by Pat Moore (Member # 380) on 12-14-2000, 09:48 AM:

John;
Actually, yes, we did. I think we've only flashed that around here in tests, though. Pretty impressive out of a 10kW light source...

Posted by Jerry Chase (Member # 660) on 12-14-2000, 09:53 AM:

To heck with the Batman gobo. What about a Batgirl gobo? I'd much rather be rescued by a batgirl than a guy in tights with an attitude.

Posted by Mark Gulbrandsen (Member # 72) on 12-14-2000, 05:01 PM:

The absolute best large wattage lamphouse I have used is the Kinoton 7KW. This thing is remarkable to say the least. At this wattage just be doubly careful of lamp focus or you will blister and cook the film. Use a heat filter in the snoot as well.
The second thing to do is trash the X-L. The water cooling simply will not cut it in the long run for a lamp this size and the side mounted "bug and crud blower" is pathetic in a drive in situation. You WILL need a projector with better water cooling to run constantly with a lamp this large. Century SAW's have really good cooling but consider installing a 70mm machine to run 35mm on. The machines are more massive and built far heavier than a measly 35mm machine, They are almost always steadier on screen as well but there are a few Italian made machines that will disprove this. A Century JJ or Norelco DP70 will most likely look far better on the large screen you have to fill. A DP70 running 35mm film is literally coasting along and if you change the oil regularly it will run forever with little or no trouble at all.
Mark

Posted by Paul G. Thompson (Member # 655) on 12-14-2000, 05:49 PM:

I think most of your problems might be in the lamphouse itself. You might want to consider an upgrade. Also, the screen might need to be repainted, and check the shutter in the Simplex. It is (at least on the older machines) adjustable. I am not certain if there is a "drive-in" shutter made for the XL or not. If you open the shutter to allow more light through, check for travel ghost on the screen. If it is ghosting, you'll have to adjust the shutter so it does not ghost. Be careful, though. If your shutter is out of time, you will have a ghost in one direction or the other, depending if the timing is early or late. (what I mean by opening the shutter is to loosen the screws on the blade and "collapse" it, then re-tighten the screws). you may want to check your shutter timing after you do that. If you look at the screen while credits are rolling, and your shutter is timed properly, if your shutter is open too much, you might have equal ghosting on the top and bottom of the credits. You might consider trying these things first before you spend a ton of money and find out that you didn't have to.

------------------

Posted by Steve Guttag (Member # 268) on 12-14-2000, 06:48 PM:

Mark, I gotta disagree with you on the scrapping of the Simplex projector. The Century has a massive block to collect the heat, Simplex tries to reflect the heat away or project it through. There is nothing wrong with using a Simplex with larger lamps, with water cooling with or without the "dirt pump!"

The big improvement will be the replacing of the lamphouse with one that gets more light out (as just about everyone has already stated). I agree that the Kinoton lamphouse is the only one I have seen/used that I would put a 7000 lamp in and run 35mm film.

I see a big improvement from going from a 4000 to a 5000 watt lamp without the big heat increase (OSRAM lamps). Christie now has a 6000 watt lamp they claim is as good as gold on the light vs heat. That is, they claim their 6000 watt lamp (CXL-60) has more light output that the 7000 and less heat.

Again, I would start the improvement in light by changing the lamphouse over to an Ultra-80 or a Kinoton Universal (easier to adapt the Ultra-80 to American pedestal).

Also, consider finding some 4" diameter lenses if your focal length is in the 7" range. The old B&L Super Cinephores are actually quite good. With really long focal lengths (greater than 140mm), the lens is a limiting factor of how much light can get out.

Steve

Posted by Gordon McLeod (Member # 33) on 12-15-2000, 09:49 AM:

In one of our old twin machine 70 3d systems we used Xebex Supersol N lamphouses and they gave excellent light with a Ushio 6K lamp
They were decomisioned because Ushio quit making the lamp
I wonder if the Christie lamp is the same one since Christie and Ushio are the same

Posted by John Pytlak (Member # 331) on 12-15-2000, 10:15 AM:

Ushio has a website:
http://www.ushio.com/catalogs.htm

Here are Christie's lamps:
http://www.christieinc.com/xenolite.htm

Posted by Steve Guttag (Member # 268) on 12-16-2000, 09:17 PM:

Gord:

Beven tells me the new "magic lamp", the CXL-60 is all new and has everything one wants without the heat...the only pain is that it is only available in an HTP package.

BEven hinted that Strong was looking into making an adapter for the Ultra-80....anything to this Pat?

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Pat Moore (Member # 380) on 12-17-2000, 07:25 AM:

Strong does make adapters for the HTP style lamps in our systems, yes.

Might be worth a discussion here. Who has experience with these types of higher output lamps?

I understand these lamps have a shorter arc gap and/or higher gas pressure -- that's what makes them "brighter". However, the downside is the arc "burns back" the cathode that much faster, so the light output degrades at an increased rate.

The current digital projector manufacturers (using DLP technology) like the smaller arc space, as that characteristic increases the efficiency of the system's light output. They also struggle with the increased arc space and deformed plasma ball as the bulb ages.

Any experiences out there?

Posted by Steve Guttag (Member # 268) on 12-17-2000, 10:34 AM:

Pat,

When you say experience with these high-output lamps, what do you mean?

Just lamps over the traditional 4KW or the new generation of lamps like the CXL-60 (or even the OSRAM XBO 5000HS)?

I have used the traditional 7000HS lamps that have been used for some time now (ORCs mostly but Christie and Osram have their offerings too). The OSRAM 5000HS is a relatively new offering and uses a very large cathode pin (where as most manufacturers have kept with the small 2500HS pin throughout the 2500-7000 watt range).

I'm looking to try out the CXL-60 and hope that there will be a CXL-60SC someday. To hear Beven speak of it...it is just magical, more light than a 7KW, less heat, longer life...able to leap tall buildings on a single drop....

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Pat Moore (Member # 380) on 12-17-2000, 11:30 AM:

I'm mostly curious about "newer generation" lamps. For instance, I understand Osram has an "SHS" lamp that's supposed to provide a more stable arc, and other manufacturers seem to be playing with arc gap space and other anode designs to improve performance.

It's pretty well agreed that (in general) light output is proportional to operating current. If a 7kw bulb is rated for 170A and a 4kw bulb is at 140A, that's only about a 21% increase in current (and light) from my experience. The big increase is in power (4000 vs. 7000), a 75% increase in energy. Most of that increase has to be in other energy, such as radiant heat, UV and IR, etc., and not just visible light that we want on screen.

What the newer designs seem to feature is a relatively higher operating current with a smaller arc gap, reducing the arc voltage. New 6kw designs probably run around the same amperage as a 7kw but with a smaller arc space -- hence a lower arc voltage -- hence the lower power rating with about the same (or better?) light output, less heat and energy, etc.

The question I have is long term operation. As the bulb ages, the cathode tip and anode degrade ("cathode burn-back"). As this happens the arc space increases, and so does the voltage across the arc. The plasma ball that produces >80% of the light from the lamp is also larger and more poorly defined, so it's not collected as well by the reflector.

So assuming the same operating current, the lamp will require more power as the bulb ages, since the arc gap (and arc voltage) increases. That sound logical?

I also don't yet have a feel for how the light output might change over time. That would be some interesting data to see.

Posted by Gordon McLeod (Member # 33) on 12-17-2000, 12:28 PM:

A question for Pat on 7K lamphouses
I have noticed that when I do the VA calculation on the pair of Ultra80's sith old style switchers I can't run a 7K bulb above 155amp to stay at lamp power of 7K
Also in one instance I tryed to overdrive the lamp but the switcher was maxed out at 158 amps with 208 line
anythoughts on this

Posted by Pat Moore (Member # 380) on 12-17-2000, 04:17 PM:

Hi Gordon;

Remember that the bulb alone is responsible for the voltage across the arc, and that's a function of arc gap, fill pressure and temeprature. The power supply only controls power and since the bulb controls the voltage, the change in power is seen as changes in current.

At 155A, 7000W of power means an arc voltage of about 45VDC. Is that what you get with a voltmeter across the arc?

The Switchers have a Coarse and a Fine control. It could well be the coarse control is set to limit output at that setting, maybe a full 4000W output. That control is down inside the switcher as I remember. I don't remember the full current output of the 7kw Switcher but it should be around 160A or so -- check the data plate to be sure.

Note that our Switchers are current-regulated, meaning that the system monitors only current output and not the voltage for regulation. That might mean this situation: a new bulb is installed and run at 140A, 30VDC on the arc (4200 watts). As the bulb ages, the arc voltage will tend to increase as the gap increases. Say it goes up to 31VDC, and the switcher is still going to run 140A, so now we're at 4340 watts without touching a control.