Film-Tech Forum ARCHIVE: Need Advice Converting Carbon Arc Lamphouse to Xenon

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Posted by Will Kutler (Member # 770) on 07-10-2003, 07:34 PM:

Here is an off the wall question for someone to answer, thanks to the bullshit politics of our local city government, which has banned the indoor use of carbon arc, claiming that it poses multiple hazzards.

So, to maintain an aesthetic appearance of a restored booth that would require more wattage than I believe the Kniesly and LPA Xenon conversions would be capable of, is it possible to insert the guts of a Strong Lume-X or Christie unit into a Magnarc or Strong Utility Lamphouse?

Posted by Jon Miller (Member # 163) on 07-10-2003, 09:09 PM:

Sorry to hear about your situation, Will [Frown]

. Ill-advised politicians just love to take all the fun out of things, don't they?

Anyway, it looks like you may have to bite the bullet and install a proper xenon lamphouse. AFAIK, the xenon conversions you mentioned are no longer made for safety reasons. Also, getting that square peg of a plenum assembly from a later Christie lamphouse into the round hole of a Magnarc would be somewhat of a challenge. Proper cooling airflow for the lamp would be another issue.

To me, an old carbon-arc lamphouse with a xenon conversion is like a vintage car with a more modern engine under the hood...it just does not have the same feel and would not be as satisfying.

Posted by Phil Hill (Member # 371) on 07-10-2003, 09:44 PM:

Will, what wattage xenon lamp do you think you will need?

>>> Phil

Posted by Ken McFall (Member # 845) on 07-11-2003, 05:11 AM:

The usual conversion of a Magnarc lamphouse in this country was done my Morganite / Thorn EMI and used a standard E53 mirror. This involved removing all of the original carbon rod mountings and gearing, extending the mirror support on rods some 6" or so forward and mounting a support assembly for the lamp with a focus control rod sticking out the front. Whilst these were used in every ABC and many Odeon and independant cinemas I thought they were awful. Any adjustment of the mirror moved it sideways or up and down so it was seldom, if ever, set up perfectly. The only way they could be setup was on the bench in the workshop. Real dogs...

The other conversion was done by a guy called Bernard Bently and sounds like it would be ideal for you. The Magnarc was left mostly untouched apart from the negative end of things which was removed entirely. The positive carrage was used to mount and clamp the lamp using the original feed control for focus.

The mirror was a full sized cold glass mirror with an aluminium ring held loosly in the middle by a spring that the lamp rested on and slid back and forth on when focused. This method also allowed for expansion of the lamp.

The strike unit was mounted inside the rear negative access door. A small external box contained ammeter, neon, hour meter and manual strike button.

The light off this was very smooth with no hot spots at all. Being a cold mirror I'm sure it could have been used up to 3k easily. The only noticable difference looking at the lamphouse was the missing feed motor and pusher rod for the negative feed.

Sorry I can't give more help but I'm sure someone on here may have more information for you.

Posted by Bill Enos (Member # 440) on 07-11-2003, 07:38 AM:

I looked into converting our Magnarcs before replaceing them. The Kneisley conversios were good for a max of 2000 watts and from what I was told by two people who had used them that they should be avoided. The convs haven't been made in more than 20 years and if you needed parts you can't make your self Kneisley no longer has any. I did see a while back a completely gutted Magnarc with ,what I believe was a 1600 watt xenon assembled inside the shell.

Posted by Paul Trimboli (Member # 1509) on 07-11-2003, 07:51 AM:

Well I know lots of people say its not a good thing, but seriously look into Metal Halide lamps. I am going to convert an ARC lamphouse into a Metal Halide lamphouse. Many have 4-7mm arc gaps so the orginal mirror can be used and with 6000k colour temp on many of the lamps makes it worthwhile with brightnesses around 110 thousand lumens. A lamp not quite that bright is around the $300 AU mark. Not sure what people have against Metal Halides. I am also going to hopefully convert an ARC slide projector to a smilar system, but with a cheaper lamp that produces 40 000 lumens.

Posted by Gordon McLeod (Member # 33) on 07-11-2003, 08:59 AM:

Bernard Bentley used the Kniesley Kit
The metal Halide is an AC arc and unless one uses a square wave ballast you will get beat flicker

Posted by Jim Spohn (Member # 1547) on 07-11-2003, 09:25 AM:

Will...I have two Magnarc lamphouses with power supplies that have been converted to Zenon that I would part with if your interested.....Jim

Posted by Stephen Furley (Member # 1277) on 07-11-2003, 02:51 PM:

Xenon lamps can evolve ozone, and they can explode. Those are multiple hazards, so why haven't they been banned as well?

Posted by Will Kutler (Member # 770) on 07-11-2003, 04:34 PM:

The requirement for this application would be much greater than 2k watts (which is what the LPA and Knisely were rated for). This is why I was wondering about being able to mount Strong or Christie guts into those c/a lamphouses. But thanks for the info everyone. I have made some recommendations to the powers that be...and the final decision is up to them.

Posted by Stan Gunn (Member # 554) on 07-12-2003, 03:03 AM:

Will I have seen a 3k conversion on a peerless some years ago; all the oridgenal parts mirror etc were left intact only the carbom holders removed, it was reported to have had exelant light output.

I have fitted smaller lamps to a viarity of lamps for back yarders also with good results, A little lateral thinking goes a long way. [thumbsup]

Stan.

Posted by Paul Trimboli (Member # 1509) on 07-12-2003, 04:46 AM:

That is true Gordon, about the square wave ballast, should not be too big a problem. What about AC arc lamps, how did they get past the 50/60hz flicker? I will post pics once I am done with my lamphouse and show people it CAN be done. I belive nearly anything is possible, just a bit of imagination is needed.

Posted by Fred Georges (Member # 505) on 07-12-2003, 09:27 AM:

I remember seeing a 1940's Arc lamp called a "Super Cyclex". It was an AC arc that used high frequency conversion in the power supply (No "rectifier" necessary) to avoid beat flicker. As an added bonus this thing could burn a bit over two hours on a single trim. Interesting. [Big Grin]

Posted by Luciano Brigite (Member # 1104) on 07-12-2003, 09:59 AM:

Converting a Magnarc to xenon isn't very dificult, I did that before and it was basicaly what Ken said in his post, the negative end goes away and the positive is kept to be used as a bulb suport(sp?).Nothing was changed in the mirror holder, only a block of heat resistant,insulating material was added in the centre hole of the mirror.a small "squirrel gage" type fan was mounted on the rear door for bulb cooling (was going to add another on the side, at the same place of the view glass but it'd flow right over the glass ball and not at the metal end.
About the metal halide bulbs,( HMI types) I also did two conversions to it, the light is about the same in color temp , I didn't really notice any beating due to AC.Both are in use for projection with small screens then I think that's why nothing was noticed. I'm not sure about the results with a larger screen. In both cases the bulbs where 1200W.

Posted by Paul Trimboli (Member # 1509) on 07-13-2003, 12:02 AM:

Great to hear HMI lamps can be used! Very interestin about the "Super Cyclex" Arc lamp, amazing what people think of, strange it never really took off though!? Luciano, do you know what model the Metal Halide lamp you used was? If it was 1200watts, that would be around the 110 000 lumen mark, you used that much light on a small screen? How small a screen? Whats the lamp life like? Which is cheaper, Metal Halide or Zenon, including rectifier/ballast?

Posted by Luciano Brigite (Member # 1104) on 07-13-2003, 12:19 AM:

The bulb used was an Osram HMI 1200W/GS. I don't have the tech data for it in hand ( it's all in a binder somewhere else) It's available in the Osram's website. Lamp life is around 1500Hours ( also have to check the tech data for it)The screen used in both cases was about 5 X 3 meters, the HMI setup ( bulb, ballast and ignitor) was cheaper than a Xenon setup. ( the ballast and Ignitor was made by myself, the bulb was around $180.00 USD)Same cooling requirements for Xenon was applied with the HMI.
Since it wasn't used in a permanent setup ( like, for a real theatrical use)the results were very good, a bit more that what I was expecting to get from it .I strongly suggest further testing with the HMI setup in order to see if problems won't develop with larger screens and/or different distances ( in the setup it was ~17 meters from projector to screen) Shutter in the projector was the drum type, not the blade ones (Erneman IV projector was used)

Posted by Jack Ondracek (Member # 1466) on 07-13-2003, 03:20 AM:

Over the past year I've seen several comments about the product output of the Big Sky company. Their early product had some glaring flaws, but they've fixed most of them, as far as I can see. After buying one unit to see if it performed as advertised, I'm replacing all of my old 4kW X-60 lamphouses with their product. They've taken the chassis that they use on many of their current consoles and have adapted it to a pedestal-mounted cabinet. The reflector (glass dichroic) is great... none of the hotspots that the comparable Strong product is putting out, and the projectors stay cold to the touch. Cooling seems adequate up to the 7kW range, so it's probably good for whatever you'd want to do. I'd bet they'd probably sell you the "innards", and you could find a way to adapt it to the Magnarc. You will have to make sure there are enough openings in the Magnarc cabinet to allow for the increased airflow you'll need for a xenon lamp. Otherwise, this is a design that lends itself well to Irem, Strong and ORC power supplies.

Posted by Paul Trimboli (Member # 1509) on 07-13-2003, 08:30 AM:

Hmm must have been very bright with 110 000 lumens on a 5 meter screen, it life is 750hours, but for the price is very good, I will have to look and see how much they are in Australia. Will give it a try, maybe I can find one that has a lower colour temp, which will last longer? SMPTE states 5200k is the lowest colour temp for 35mm.

Posted by Luciano Brigite (Member # 1104) on 07-13-2003, 10:28 AM:

Ooops.. my bad about the bulb life.
FWIK.. the HMI bulbs are all in the 6000°K range. some will go to 6500°K ( there are differences in color temp. depending on bulb wattage and even more from one brand to another, even if their tech. data says 6000°K . I noticed it between Osram and Ushio bulbs, both of 1200W.)
Forgot to say that the same care in handling for Xenon bulbs apply to HMI, they're smaller than Xenons and doesn't seem to have all that pressure inside but they will fail about the same way if you leave finger prints, etc on it and the cooling isn't enough.
Also.. they'll take some 5 minutes to reach the full output and if you shut it off, you'll be able to re-strike it only after 12 minutes or so.

Posted by Robert Throop (Member # 61) on 07-13-2003, 07:18 PM:

The Cyclex was made by Ashcraft and used a special 96 cycle motor generator to avoid flicker.

Posted by Gordon McLeod (Member # 33) on 07-14-2003, 08:10 AM:

Any bet if you are not getting a beat flicker it is becasue you are on a 50 Hz power source and the projector is probably running very close to 25 FPS.
therefore no beat
can't be done though on 60 hz mains with 24fps without square wave powersupplies as are used for northamerican film production
Also the cost per hour of operation is much higher with HMI than with xenon and as they age the colour temp actually rises

Posted by John Pytlak (Member # 331) on 07-14-2003, 02:08 PM:

quote:
If it was 1200watts, that would be around the 110 000 lumen mark

No Way!

Even the largest 7000-watt xenon lamps used for film projection today put only about 20,000 lumens on the screen.

Posted by Michael Harlow (Member # 1353) on 07-14-2003, 04:57 PM:

John P. I will check for sure but i am sure that the Philips 1200w MSR lamp reaches nearly 110,000 lumen. I have these in some lighting effects in my club. They are similar to HMI but more rugged. I'll checkk the tech data.

sorry, just checked. 110,000 max luminous flux, peak 20,000 cdl.

Posted by Luciano Brigite (Member # 1104) on 07-14-2003, 09:19 PM:

Frequency here where I am is 60 Hz. I can't say anything about the speed the projector was running since it wasn't me who set it up.
If I remember it right, the HMI bulbs are around the 11.000 lumens.. not 110.000 ( I sure need to organize my tech papers a lot better..couldn't find the tech sheets for the HMI bulbs)

Posted by John Pytlak (Member # 331) on 07-14-2003, 09:22 PM:

The discrepancy is that you have to focus that light through the aperture, shutter, and onto the screen. Your 110,000 lumen number is TOTAL output, not focused.

Posted by Luciano Brigite (Member # 1104) on 07-14-2003, 11:18 PM:

I need to make a note to myself to not post anything when I'm tired and nearly falling asleep.. i'll end posting things a bit out of the way or forgetting things.

Now I have a question about the Magnarcs.

A few months ago I received a lamphouse, it's not the real Magnarc, but it's a clone of it on everything save fora few minor differences in one thing or another. Well, the curious thing is, it was "converted" by it's previous owner to use an HMI bulb and about everything inside of it is gone, even the positive clamps. I'm working on it now (rebuilding it) and making it ready for xenon.while de- assembling the thing I noticed that the magnet is gone and it's used with the xenon for arc stabilization (sp?) My question is:
What I can use in place of that magnet? ( the original Magnarc has a permanent magnet, this one I believe had one the same way and not the high current cable coiled around a iron bar behind the mirror)

Posted by Paul Trimboli (Member # 1509) on 07-15-2003, 03:10 AM:

Hmm so that lamp produces 110 000 lumens, so after it goes through the projector what would be the lumen output? How many lumens does it take to say illuminate say a 10meter screen?

Posted by Scott Norwood (Member # 30) on 07-15-2003, 04:56 AM:

Stupid question: why does [dlp]

require more light than film for the same size screen? With film, 50% of the light from the lamp would be lost at the shutter, while DLP has only the DLP chip and the lens (and port glass and screen) to suck up light. Is the DLP chip itself that much denser than film? Or is there some other reason that I'm missing?

Posted by John Pytlak (Member # 331) on 07-15-2003, 06:08 AM:

It's a matter of optical efficiency. The chips are only part of the optical path. Remember, you have the reflector, heat filters, integrating bar, dichroics to split the light into red, green and blue, the lens, etc. With film, you just have the reflector, the shutter, the film, and the lens.

Approximate lumens required to illuminate a matte white screen to 16 footlamberts is (area in square feet) x 16

Posted by Gordon McLeod (Member # 33) on 07-15-2003, 10:25 AM:

D cinemas big light eater is the fact that there is polarization used in the beam spliting system