I like the system Osram uses on their 1600-watt and smaller bulbs for rotation. Install the bulb with the washer in place on the negative end. At half-life, disconnect the positive clamp, unscrew the bulb, and throw the washer away. When you screw the bulb back in, it will automatically have rotated 1/2 turn. With our booths being operated by those with less experience than in the past, this is probably a good thing.

I agree with both Joe and Gord that flicker problems may occur unless the bulb current is raised for a short period (a day or so) to allow the new position to "set".

But this might not be good for everybody. Now, I don't know this for a fact, but maybe it works this way:
Let's say at lamp "A," the temperture at the bulb seals runs at 75% of max. allowed. When the fans are shut off at night, the temperture rises to 95%, but then starts to cool down. No problem.
At lamp "B," the temperture at the bulb seals runs at 85% of max. allowed, cause the fan is not so good. When the fans are shut off, the seal temp goes up to 105%. Not good.

Personally, I think the bulb temp should remain the same at all times, as much as is possable. So if I worked at theater "A", I would just shut off all fans between shows. That way, the bulb doesn't cycle from cold to hot, over and over.

We had 4 Zenith/Cinemecannica lamphouses with that Osram 1600 watt lamp with the spacing washers. I know I sound like I'm lazy, but it was a hassle to deal with them. There was no support at the + end, so you had to be careful disconnecting it because the threads get corroded. The plastic cover the bulb is shipped in is also needed as a removing tool, and someone would throw it away. When you are an in-house tech and trying to keep 35-40 screens running, you want to get rid of these kinds of "nuisance" maintaince items, however small.

I doubt that that little nib where the air is sucked out is weaker than the rest. I would think it would be stronger. I sure it would be mentioned in the installation procedures if it were true. Can't hurt, though. Of course it also doesn't matter which way a bulb is rotated, but you might make up your own bulb record chart stating clearly which way to go. Don't forget to put your name and phone number on it for a little "polite" advertising.

As far as cutting off the nib to de-gas the bulb; holy smokes! You seem like a nice guy to me, but that fellow must really dislike you. I wrap them in several layers of newspaper, and they still shred the paper when exploded.

I don't know if any of you have a cfm meter, but I would highly suggest it. They are not too expensive - $300. In the Xetron lamp support manual, they suggest 500 cfm for a 4000w lamp. If you specify that during construction of a new theater, it's great to be able to stick that thing in there and turn to the HVAC guy and say, "Not enough." Then turn directly to the owners and say, "Please don't blame me for bulbs dying early. It will cost you X amount extra over the next 5 years because this fan doesn't meet spec."

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At my theatre, we have it set up so that when you shut down the projector and turn off the exhaust switch, the exhaust actually stays on for 10 minutes before automatically shutting off. So that way we can just go home and the bulbs still get adequate cooling. Like I said before, I get AT LEAST 1300-1400 hours out of a 4000 watt bulb (in the worst case scenario) so I don't think I'm doing anything wrong.

Is there any scrap market for used tungsten electrodes? Does Will Rogers charity collect them for scrap value, as they used to do for copper drippings from carbon lamps?

Would NEVER even think of throwing out an old bulb without breaking it first. Likwise, would NEVER risk injury by breaking the bulb without having it in its' protective case and several layers of canvas. We wear the full "regalia" of protective clothing whenever we handle a bulb, including full face shield, "gauntlets" that extend up the wrist, and ballistic nylon jumpsuit. We want to keep both eyes, and not spill any blood.

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John Pytlak, Senior Technical Specialist
Worldwide Technical Services, Professional Motion Imaging
Research Labs, Building 69, Room 7419
Eastman Kodak Company
Rochester, NY 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243

Oh, no, I agree. I didn't explain myself too well. I just meant that if the temp doesn't get too high, I would just shut off the lamp and fans. Ideally, it would still warm when the next show started. Remember those "instant-on TV sets?"

I once took one out back of the house, into the woods and shot one with a .22 rifle. It was pretty cool, although it would have been a lot less cool if I wasn't 100 yards away from it when it shattered. Some good-sized chunks of glass flew almost 20 feet.

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In the CFS (4200watt) lamphouse, there is a blower pipe that feeds air to the bulb. It somehow got turned so that it did't point at the bulb anymore. We had a series of bulbs that didn't last very long. (Less than 500 hrs.)

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