Don't ask me why so many different wattages for a 5-screen theater.

As I was rummaging through some old bulbs, there was a clear 4500 watt and a clear 3000 watt lamp sitting in the pile. I noted one 4500 watt lamp was pulled after 6,600 hours. The 3,000 was pulled after 3500 hours.

The remaining bulbs had well over 4,000 hours on them. Only two looked real bad, probably because they were operated out of parameters. When looked the booth over before we took over, I noted that one of the 3000 watt lamps was being operated at 125 amps.

One of those bulbs was from that lamp.

Now, the lamp exhaust......they are belt-driven with a 1/2 (maybe 1/3) horse motors. When they are all running, it sounds like a Diesel Locomotive rumbling through the booth. That's how big they are. The proof is in the pudding.

Oh, by the wey - they are Christie bulbs.

The draft at the console stacks is almost strong enough to suck your hand in. The duct work from the lamphouse to the fans are 12 inches in diameter. Very impressive cooling for the consoles.

Actually, I like the Christie Consoles, but as for the projectors, well.....that's a different story.

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It is our company policy not to rotate. I do believe the theory behind this is that the arc has found a spot where it likes to burn. It is happy. Rotate the bulb, and you scew that up. Does that make sense? I think so.

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But it does not sould like the same type of getter Richard speaks of.

With limited manpower and a large number of screens to service, we don't often get out to perform routine service (at least the way it should be done) as often as we should, especially in out-of-town situations.

A manageress/projectionist in one of these locations asked me if I would change 4 of her 6 xenon bulbs for her. She was quite capable of doing it, but hey, since I was there anyways... She informed me that these four machines had not been changed since she was at the theatre, and had no idea as to their age.

I replaced these bulbs. Although they were dark on the top (obviously never rotated), the screen light wasn't that bad, and had very little, if any flicker.

In one of the lamps i found a xenon bulb record sheet. It had been filled out by a former union projectionist I know. I checked the serial number against the bulb I removed. Sure enough, this bulb, an Osram XBO 2500 W/hs, had approximately 7500 hours on it. Same with the other three lamps.

I attribute this not only to adaquate ventillation and quality Osram bulbs, but Strong switching rectifiers as well.

I think it boils down to cooling, the quality of the xenon itself and the power supply driving the lamp. Nothing beats a Christie lamp in a Christie console. When working with other brands of lamphouses, I have been able to greatly improve lamp life just by increasing the CFM of the exhaust. Switching to Christie lamps helps too, but boost the exhaust and you'll probably be very surprised.

On a related note, even though this thread is specifically asking about rotating xenons, do be sure and take a good hard look at your lenses. I work 2 nights a week at the Galaxy and our scope images are incredible. However, our flat presentations make me want to run and hide. This is because we are using those damned Magnacom zoom lenses for flat!!! These things suck up light, resolution and even produce dark corners that is NOT the bulb being focused down too much. I brought in a regular 35mm lens a couple of years back and did side by side comparisons in the turret and the difference was like comparing 16mm to 70mm. Maybe Regal will fix this once and for all. (Hint, hint) Anyway, check your lenses (clean them too, of course), as well as the reflector and port glass if you are getting poor light on screen.

Brad -- interesting comment on the Magnacoms as a light eater. They were usually fairly efficient in my experiences with them. The theory was, of course, to use them with longer focal length prime lenses that generally had better depth of field and light throughput compared to fixed focal length prime lenses of the day.

Are the screens they are in using vertical masking? What's the prime lens they attach to? The dark corners might indicate some vignetting, which might be the Magnacom attached to too short a prime lens without the proper adapter to "close couple" it.

Don't get me wrong -- the newer fixed primes are generally a much better option, especially the PLUS lenses. The instances where I'd use a Zoom Converter (new version of the Magnacom) with a Prime lens are fewer.

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A few years ago I took up a 35mm lens of mine and placed it in the scope position on the turret of a couple of projectors and flipped back and forth. While my picture was a bit too big for the screen, even with the extra magnification my lens was substantially sharper and brighter...and this was not me being picky. To keep the picture from hitting the lens barrel, whoever set up the lenses had to use an appropriate focal length prime lens so that the Magnacoms were as compressed as much as they could possibly be. Otherwise the picture is literally a circle. Still though, the clearance is so tight that even illumination in the corners is impossible. I'm not sure if the lenses have close couplers on them or not, I know we have them on our scope lenses, but I'd have to check the flat.

While I do agree the newer versions of Magnacoms are much better, this is just not the right way to do it. We have one house in the complex that runs with a fixed lens and that flat image is fantastic, despite top masking being in all auditoriums. And of course, ALL of our scope images are great.

(Just imagine how great flat films through a zoom attachment look with a 4500 watt xenon onto an 80 foot screen! )

The reason for me throwing this question out here is because at this theater in Anacortes where I am now, we didn't have any vignetting until a bulb blew. It wanged the mirror so bad, it was junk. I sent you a picture of that mirror last month some time.

I temporarly replaced the Super-Lumex with an ORC XH series lamphouse, and I had no vignetting. When I replaced the mirror in the Strong and placed the unit back into operation, still no vignetting, except I had to re-trim the scope aperature about .001 inches on the sides. With the old mirror, I tried just about everything in the books to eliminate the vignetting.

Correct me if I am wrong, but I have heard that the f-stop of the mirror and lense should be as close as possible.

As per example, a 500-watt Kneisley has such a fast mirror that it seems impossible to get rid of a hot-spot on the screen when it is sitting behind a 35mm projector. Would a faster lense correct some of this problem? I am under the impression the f-stop of the lense should match the f-stop of the mirror as close as possible.

I have a lot to learn here....... Thanks

We need a "Lense 101" seminar in the tip section of FT.

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I have also found that Magnacoms do not perform equally across their range and depending on the geometry of the your screen system, it is better to favor nearly pulled out, nearly pushed in or somewhere in the middle. I would not dismiss Magnacoms out of hand though. They are not necessarily the best choice in all situations either.

Give a Flat or nearly flat (1/20) screen a standard fixed focal length lens will normally be the better choice, if you can get the image out of your projection system.

In some instances, I've had to use the little known .52X magnifier by ISCO...it comes in a type "F" for flat field (also the shallow curves) and a type "C" for deeper curves. One thing that baby will do is push the focal point forward and also not eat any light (it is a large and expensive piece)...for pictures, check out the Indianapolis IMAX 3D in the gallery here...there is a picture of the Norelco projector with it (a white lens cap is on it).

The new Zoom Converter type "S" has a much larger exiting element than the older Magnacoms so even short lenses will not have a vignetting nor light problem.

Steve

The story I got from one of the techs who did the installation as to why we have all of these Magnacoms was that the wrong fixed lens sizes were calculated and when it came time to open and the installers found out the fixed lenses did not fit the screen that there was a mad panic of grabbing at zoom add-on lenses and older, longer focal length lenses that were laying around to get the theater open. According to the manager, some of the screens could only run scope films for the first couple of months because of this.

Adding to the craziness, apparently upon opening they burned a print in one of the large auditoriums on a 6000 watt bulb and the entire picture was shaking from the blower on the lamphouse. The solution? A smaller blower and 4500 watt lamps from that day forth. I installed the exact same make/model console last month at a theater with a much smaller screen using a 6K xenon and had no problems whatsoever. For reference we are speaking of the Christie SLC-45.

Close couplers are not expensive...give it a try.

Steve