Film-Tech Forum ARCHIVE: 4000 Xenon at 105A

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Posted by Antonio Marcheselli (Member # 373) on 05-19-2001, 07:02 AM:

Hello everyone.
I found in a theater os my chain an Osram Xenon 4000, that should run at 135A nominal (80-150 range), working at 105A.
If I would make a comparison with another lamp, how much brightness I'm loosing? Can I say "It is working like a 3000W xenon lamp"?

Bye
Antonio

Posted by John Pytlak (Member # 331) on 05-19-2001, 07:20 AM:

In xenon lamps, light output is generally proportional to power (watts = voltage x current). So running a lamp at lower current will give lower light output, proportional to the power being consumed. Lamp current can be adjusted to "fine-tune" light output, as long as you stay within the specified current range for the lamp. Many recommend using a new lamp at about 85% of its maximum rated current, and increasing current to maintain light output during the life of the lamp. Never exceed the maximum rated current for the lamp.

------------------
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 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Antonio Marcheselli (Member # 373) on 05-19-2001, 09:01 AM:

Thank you John.

But I read on Osram "operating instruction" that running a xenon lamp at a lower current than nominal will not increase lamp life.
Since 4000's maximum power is 150A why not install it at 135 and raise up to 150 if necessary?

However, in you opinion, running a 4000 Osram Xenon bulb at 105A can make sense? If current follow power proportionally, so their lamp is giving about 3000W...
And since they have brightness problem I don't understand why they should keep it at 105A, what do you think about?

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 05-19-2001, 09:29 AM:

I think the lamp would tend to blacken prematurely as well as be slightly unstable.
It will also be produceing less light than a 3K would running at 105 amps

Posted by Darryl Spicer (Member # 711) on 05-19-2001, 01:43 PM:

what you want to do is maintain the current voltage so that when multiplied by the amperage it totals as close as possable to the total wattage of the bulb. this is how it should look

dc amperage =135
dc voltage = 30
total watts= 4050

If you can maintain this you will be fine. You will be apperating within the recomended current settings.

Posted by Gordon McLeod (Member # 33) on 05-19-2001, 02:09 PM:

Actually Volts x Amps can be incorrect for depending on several values either the volts or max amps would have to be exceeded to get the desired VA

Posted by Darryl Spicer (Member # 711) on 05-19-2001, 03:05 PM:

those lamps are tested before shipping they come with a test sheet that tells the volts and amps that the bulb was tested at multiply this and see what the watts are. You should be running somewhere close to this.

Posted by Gordon McLeod (Member # 33) on 05-19-2001, 03:50 PM:

That information is based on a given test system. In fact different lamphouse/rectifier combinations will vary from that, even exhaust airflow will vary that.
The important issue is not the watts as based on VA but that neither voltage nor amperage maximums are exceeded

Posted by Antonio Marcheselli (Member # 373) on 05-20-2001, 05:44 AM:

Another question about this 4000. Yesterday has been raised to 135A without problems.
I would like to align the lamp again. With a 4000W how much time can I keep the lamp projecting into the lens (without any prints and with projector running) before having damages? I wonder this because at my booth I have a 2500W and I really don't want to create any damage with a 4000W.

Thanks
Antonio

Posted by John Pytlak (Member # 331) on 05-20-2001, 06:37 AM:

With that large a lamp, I would keep each session to less than 30 seconds, with a few minutes for the lens to cool down between sessions. Following the alignment procedure outlined by Pat Moore (string/laser alignment first, then "bullseye" technique without lens, then final touchup with lens), you really shouldn't need more than a few 30 second sessions to fine tune the alignment. I'm sure others who do this on a daily basis will have more "hands on" suggestions.

Posted by Darryl Spicer (Member # 711) on 05-20-2001, 10:18 AM:

Yes you should remove the flat lens and bullseye the spot on the screen. The black circle should be as round as possable and not have black rings around it. Then switch lens to scope and fine tune the light output using 30sec intervals to protect the lens. I also run a large test loop thru to make sure that there is no scorching of film. and to check for focus flutter. this is also good time to reset the focus on the flat lens so the film does not start out of focus.

Posted by Gordon McLeod (Member # 33) on 05-20-2001, 12:11 PM:

Since you have I believe mentioned you have cinemeccanica they use a crosshair sight system to align the lamphouse.

Posted by Antonio Marcheselli (Member # 373) on 05-20-2001, 02:17 PM:

Thanks Darryl.

Gordon,
Yes, it is a Cinemeccanica V5.
Should I know something about the "crosshair sight system" of that projector to align better the lamp?

Bye
Antonio

Posted by Antonio Marcheselli (Member # 373) on 05-24-2001, 12:52 PM:

We put the lamp at 130A and the result is stunning. We have to thanks Cinemeccanica that installed that lamp few months ago.
However I've noted that the amperometer arrow is not very stable. It is moving slowly in a +/- 2-3 Ampere range.
My two 2500s are more stable. Is it normal on higher power?

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 05-24-2001, 02:49 PM:

Is there any flicker?
It may take a few days for the lamp to stabalise at the new current

Posted by Antonio Marcheselli (Member # 373) on 05-24-2001, 08:01 PM:

Yeah,the light is not very stable. It has never been stable... But I'm not the projectionist of that theater and perhaps the lamps were always at 105A...

I will let you know in the next few days!

Thanks to everyone for the help.

Antonio

Posted by Antonio Marcheselli (Member # 373) on 05-25-2001, 11:06 AM:

Yuhu!

I found that our rectifier handles 80-100A so it can't handle a 135A 4000W lamp.
They have Osram 4000 since 3.5 year. A LOT of money wasted.
I hope that someone will pay for his mistakes.

Bye
Antonio