I need your help. Someone will remember my questions about lamps alignment and lamp problems in the past. Unfortunately my booh (my ex- boot, I do not work anymore for that theater but I'm still in contact with the management) is a pain in the ass, every day a new problem comes out...

Ok, we darkened a lot of Osram 3k lamp recently. We have a new one since 15 days and it is again darkened. Just a bit, but it is just 15 days old and it shouldn't
A tech comes to the theater to check. The amperometer says 100A, the specs says 100A, 30V. He connected a tester on the rectifier output (IREM) and he measured 32,5V. If math is not an opinion 32.5V is 108A. if we set the rectifier output to 30V the amperometer says about 80A. The first thought is that the amperometer is faulty or the shunt is not set correctly.
Ok. What is the problem? At 30V the lamp has problems to strike. And, more in general, it has BIG problems to strike when hot (also at 32.5V). We have to wait 3-5 minutes before strike again when hot.
This, I believe, is not normal. What could be the cause?
And, do you believe that I should follow the amperometer or the meter (30V)?

More: we have heat filter on the lamphouse. We tried to remove them, the light has a better color temperature. With the optical glass we installed 2 weeks ago and without the heat filter the image improved DRASTICALLY.

Do you believe that we can go without the heat filter?

Thanks for your help.

The current is the operative one to look at. You can always verify that the ammeter is reading correctly using a calibrated ammeter but most of the ones in the lamphouse are accurate enough.

Steve

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V=I*R (or I/R? ), right? Do you mean that each lamp can have a different resistance and the Voltage measurement isn't precise enough?
And what about the darkening? Can I connect an amperometer on the rectifier wires to check the current?

Paul, I always forget what mirror is cold and what is not. Ours is glass made.

What kind of lamphouse do you have? Maybe we can get an idea if you have a cold reflector or not. Since your lamp apparently came equipped with a heat filter, you probably have a hot mirror. Running without the heat filter will make the film trap too hot, and the infra-red from the bulb will damage the film.

If your bulbs are turning dark in such a short time, I would highly recommend you check the lamphouse venting. It may be running too hot. Check the bulb focus, too.

Once I have heard that an out-of-focus bulb can be damaged by the infra-red spectrum being reradiated back into the bulb by the reflector. This might be a myth, since nobody ever confirmed or denied it. But it makes sense to me.

Actually, power is the product of voltage and amperage. (P=IE)
or P = Current squared times resistance. There are other ways to jostle that formula around, but the two I mentioned are the most common.

The lamphouse should be the 7040H, the projector is a Cinemeccania V5.
The mirror, if I remember correctly, has a green color.
Initially the projector came without heat filter. Was needed because we burned a lot of movie. But at that time we had a 4000k (now 3000k) and the lamp was COMPLETELY out of focus with a beautiful hot spot on the print.
Without the heat filter the image is better, the gate is hotter but the print exits the projector just warm.
A cinemeccanica tech I spoke with today told me that it could be the capacitor of the IREM. A bad diode is easily seen on the screen (and, I replaced all of them recently), and a bad (striker?) too.
He told me that the voltage I measure on the rectifier isn't important.

I remember (with old diodes, I didnt' check again) that I measured about 1V of AC on the rectifier output. He told me that it is too much, should be 200,300mV.

Pls give me your opinion, this problem MUST be solved.

THANKS!

Since infrared energy is being removed from the light beam, it needs to be directed to a heat sink. Dichroic heat filtration is definitely recommended for a 3000 watt lamp.

As far as premature lamp blackening, if you know that excess current ripple is not eroding the electrodes, check the lamp ventilation. Excess air flow can be just as bad as overheating, as the evaporated tungsten builds up on the cooler quartz lamp.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

John pointed out:

quote:

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"As far as premature lamp blackening, if you know that excess current ripple is not eroding the electrodes, check the lamp ventilation. Excess air flow can be just as bad as overheating, as the evaporated tungsten builds up on the cooler quartz lamp."

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This brings up another point: The lamphouse was designed for proper air flow with all the devices installed. Removal of the heat filter may upset the cooling balance and proper airflow over the bulb.

However, I don't think the igniter has that much to do with the bulbs prematurely darkening. They just fire the damn thing.

I agree, there could be some bad filtering in the IREM power supply, or possibly a weak doide or two. IREM's have been known to be "dirty" anyway.

John,
Yes, the air into the lamphouse has been recently increased but, I believed, it is not excessive. Has been increased because there was almost NO air extraction from the lamphouse for years. Do you know the black plastic handle outside the lamphouse? It is melted. Now the externat temperature of the lamphouse is just hot but not so hot!!
We will check the print temperature and we will decide if the heat filter has to be reinstalled or not.

About the problems striking the lamp... We could change the capacitors. If anyone has a different idea is welcome!!!

Although I think the stack temperature is still too high, that Christie bulb in one specific lamp has over 3,000 hours on it and the light on the screen and the bulb's envelope still looks good. As far as the other lamps are concerned, they are still in the "testing and evaluation" stage.

Ok, I'll let you know.

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I've experienced a similar problem but in a Highlight 2 console from Strong: The lamphouse was hot as hell and the bulb was over heated. The mirror , a cold one, made of steel and special coating. was dammaged too. Te problem will appear since the day we put in this lamphouse a 7 kW xenon lamp ! Imposible to achieve a good focusing of the light ! The problem came from a mechanical reason: the carriage of the lamphouse was to short to handle a big xenon lamp like this one. Previously we had a 5 kw lamp and the adjustement was perfect.
Check the distance between the "ass" of the mirror and the film: It mus be for a 15" mirror, a distance of 84.15 cm (± 33 1/8") preconised by Strong. From years I Worked with a Zenith 6500 H on my's V8 but with a 3000 W xenon...
And Please don't remove the heat filter, just replace it, if marked..

Hope that you help, Sorry for my really BAD and Weak English

Is the heat filter damaged in any way? That might account for the drastic change in light when it is removed. My understanding is a heat filter will reduce the light by about %10, but will reduce the heat by about %50. Is the filter put in the right way (coating towards the lamp? (We run 3000 watt lamps without heat filters or water cooling and it runs OK (Neumade/IREM consoles and Osram bulbs.) A water-cooling assembly is available for V5's. It's really just a metal plate with an aperture in it and a loop of copper tubing that goes around. They might not be too expensive, and are fairly easy to install.

Use a different amp meter to verify the current is not too high. Prehaps you could temporally change the amp meter and shunt from another lamphouse to test. If that looks OK, the tech should look at the power supply output with an oscilloscope to check ripple. IREM power supplies have a small circuit board with a relay ("RA relay") It controls the bulb ignition pulse. Again, you could temporally swap it with another and see what happens.

Check the roof exhaust fan. It should be above 500cfm or so. Many times the owner will cheapen out and install a smaller fan. They do this because they have to pay to heat or air condition the air, and the lamp fan just sends it outside. (We specify about 700-900 cfm for each lamp exhaust, which does get expensive. Sorry for not having the metric equivlent of cfm's (feet per minute.) Does the lamphouse have it's own fan for exhaust? Are there other fans for supply? Are all fan blades clean? Is it possible that the fan(s) turn off while running a show. (This happened recently to me: A lamphouse we have has three fans in it. One fan would overheat and the thermal protection device inside it would shut it off. It would cool down, and come back on again. There was so much airflow from the other fans, the safety vane switch would stay in position and not shut off the lamp.)

Are other projectors affected? Could the air supply into the booth be blocked preventing air flow to the projector?

You said;"... the air into the lamphouse has been recently increased.." What did they do? Could someone have done something that causes turbulence? Generally, the orginal lamphouse design was pretty good. Why did it not work correctly when installed?

IREM ignitors have a spark-gap device. It's in a round, clear plastic peice that snaps onto the ignitor. Temporally swap it with another to see if the bulb ingites better.