Film-Tech Forum ARCHIVE: 7K Xenon Anode Damage

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Posted by Andrew Shingleton (Member # 2257) on 07-19-2004, 07:13 AM:

Hi guys,

Here is a photo of an Osram 7000W xenon which we recently removed:

Close up of the anode after we broke the lamp for disposal:

This lamp had done 1114 hours at 150amps.

It actually looks more dramatic than that in real life - it's hard to get a proper representation of it in a photo, but those growths at the end are about 3mm high, and under the large shiny part in the middle is actually a deep pit (a few milimeters deep at a guess).

Was just wondering if anyone had any thoughts on what the major cause of this would be. Is it simply because the lamp was well over it's rated life (by 614 hours)? Do we have a current ripple problem? Could it be from under or over cooling? We have two 7K houses, but the house this lamp was from always ends up with far more dramatic anode damage than the other house does.

Opinions would be greatly appreciated. [Smile]

Posted by Michael Schaffer (Member # 1204) on 07-19-2004, 07:27 AM:

You said it yourself. More than twice the rated lamp life. If the marks were very irregular, you might have a misaligned lamphouse (e.g. magnet). But these marks look normal. I wouldn't run the Osram 7k longer than 800-900h.

Posted by Liam Utley (Member # 1931) on 07-19-2004, 07:39 AM:

That looks fairly normal for an osram 7K. 1114 is a lot of hours for those lamps, I've seen worse than that after 700 hours.

Posted by Steve Guttag (Member # 268) on 07-19-2004, 09:31 AM:

Gosh, you guys are pretty easy on OSRAM...That lamp looks like excessive ripple. I'll say this...none of my Christie's have ever looked like that when they came out at just 1000 hours.

Steve

Posted by Gordon McLeod (Member # 33) on 07-19-2004, 10:00 AM:

What make and model of Lamphouse and rectifier are involved

Posted by Andrew Shingleton (Member # 2257) on 07-19-2004, 10:10 AM:

Ahhhh, I knew I forgot something... I worded this post in my head while I was threading tonight, and I remember thinking to myself I must remember to mention the lamphouse and rectifier type! [Smile]

Cinemacannica lamphouse, and I haven't checked the rectifier model but it's probably cinemacannica too (assuming they make them). I'm at home now but I'll check when I'm in tomorrow.

Posted by Oliver Pasch (Member # 1335) on 07-19-2004, 11:11 AM:

Besides that 1114 hours really are a word, you should check whether the magnet to stabilize the arc is correctly aligned, as Michael mentioned before. Recent 7000HS from this manufacturer tend to be a little sensitive here and seem to need more stabilization than before - don't ask me why. We're running lots of them in Kinoton-lamphouses (by the way: at 160 A) where they tend to flicker pretty early if not properly aligned, actually it's sometimes almost impossible to calm the arc using the standard-magnet.

Posted by John Pytlak (Member # 331) on 07-19-2004, 11:24 AM:

Not too bad for that number of hours. Since the erosion is well-centered, the magnetic stabilization is likely Okay. Less current ripple will always help.

Running to 2X rated lamp life entails more risk. [Eek!]

Posted by Andrew McCrea (Member # 674) on 07-19-2004, 07:54 PM:

Is the rectifier the power supply or is it the part in the lamphouse that holds the xenon, located behind the refelctor?

BTW, I'm 17 tomorrow [Wink]

Posted by Aaron Sisemore (Member # 145) on 07-19-2004, 10:38 PM:

Andrew: In the context of cinema equipment, rectifier=power supply.

Happy bday.

-Aaron

Posted by Steve Kraus (Member # 476) on 07-19-2004, 10:41 PM:

The rectifier is part of the power supply although as the term is used above they are meaning the power supply as a whole. A traditional power supply contains transformers, rectifier (a set of silicon diodes), a power contactor (a relay that lets a simple 120V circuit turn on the big power), filter capacitors and chokes and an arrangement to create a boost voltage to help the bulb start, and, often, a cooling fan. Regulators are sometimes used but this is less common. Newer technology uses a switching supply akin to what you have in your computer.

The lamphouse contains: The bulb, reflector, cooling fan & safety switches, high voltage ignitor, current meter (and sometimes voltmeter or a switch to enable one to do both), hours meter and a douser (door at the front).

The power supply often sits on the floor near the lamphouse or can be off in another room. However, many theatres use consoles which take the place of a traditional projector base + lamphouse. The top of the console houses the lamp components while the power supply is in the bottom. Often some open rack space is left which can be used for sound equipment (if the system isn't too elaborate), automation, etc. The projector or projector + soundhead bolts to the front of the console the same way it would attach to a standard base.

Posted by Jack Ondracek (Member # 1466) on 07-20-2004, 12:15 AM:

I've run 7kW bulbs by Superior Quartz and Christie in Strong and Big Sky lamphouses, using both switchers and boat anchors. I have yet to see this kind of pattern on any of them. The anode eventually gets a "scuffed" look to it, but nothing like the gouge and build-ups on Andrew's. Pretty interesting.

Posted by Chris Hipp (Member # 1788) on 07-20-2004, 12:25 AM:

I think that it is just simply that he bulbs was in there for so long. However, any time you suspect a lamphouse issue always check for proper cooling. I can't tell you how many problems I have seen just because one show ran without the exhaust fan working.

Posted by Stephen Jones (Member # 16) on 07-20-2004, 08:13 AM:

Hi Andrew,
By the looks of your pics I would say the lamp has gone way past its service life you are lucky to get that number of hours from a 7K lamp.I removed one here yesterday that had 1900 hrs up we usually get about a 1000 hrs from them.The info I have from Osram is that a 7k lamp service life is 500hrs anything past that is a bonus.They usually start to flicker at about 800hrs which is when I usually remove them but lately they havent been doing that till about 18oohrs.Cinemeccanica consol's and Kinoton consol's use IREM rectifiers.
If you want infomation on correct operating amps etc for your lamps contact Atlab or Cinetech or the Osram rep here in Melbourne they would be happy to give you any advice.The Osram rep was at my location last Friday.If you need contact Numbers etc let me know.

Cheers,

Steve [thumbsup]

Posted by Andrew Shingleton (Member # 2257) on 07-20-2004, 06:21 PM:

By contrast, here's a photo from the xenon I removed from our other 7K house (Cinema 2) this morning. This bulb had done 1669 hours at around 150amps! [Eek!]

The anode on this bulb is a lot different to the anode on the other. As you can see this one does not have the same types of random growths on it, but instead has formed a deep pit. This is how most of our 7K's end up, and is what usually also happens in Cinema 1 (the photo's in the first post being an exception). Generally we get better performance out of Cinema 2, but not by much.

There was not a huge amount of arc flicker in Cinema 2 despite the large number of hours it had done. The quartz envelope is not even that dark, and the light output was not perfect but was still acceptable.

In a perfect world I'd like to change the bulbs a lot earlier than we do, but someone's gotta pay for these expensive things and they don't like buying a new one every month. I won't go into that here though, but I'm sure everyone is aware of the fun that budget restrictions cause... [uhoh]

Stephen, just wondering, what percentage of rated life do you usually let your bulbs run to? A lot of places in Australia tend to run the lamps for quite a long period of time from what I've gathered. Could there be something different about the quality of our power? I wouldn't have thought so, but I guess it's a possibility.

Thanks to everyone for their input! [Smile]

Posted by Gordon McLeod (Member # 33) on 07-20-2004, 06:44 PM:

"In a perfect world I'd like to change the bulbs a lot earlier than we do, but someone's gotta pay for these expensive things and they don't like buying a new one every month"
Sorry but the bigger the lamp the shorter the life span and that is just part of the cost of doing business. If they want big screens then they need big lamps and regretably big costs to go with it

Posted by Andrew Shingleton (Member # 2257) on 07-20-2004, 07:14 PM:

Well, to be fair we're sort of in a transitional phase at the moment and things budget-wise should get better soon. But it's funny how that logic is so glaringly obvious to anyone technically minded, but often doesn't make a difference to people who only look at the bottom line.

Posted by Chris Hipp (Member # 1788) on 07-20-2004, 07:20 PM:

quote: Andrew Shingleton
Stephen, just wondering, what percentage of rated life do you usually let your bulbs run to?

I would only push a bulb to about 25% of its rated life, so if it is rated to 2000 I would try to get 2500 out of it. However, I know that 2k bulbs in christie SLC consoles typically last two or three times their rated life.

Posted by Stephen Jones (Member # 16) on 07-20-2004, 08:39 PM:

Hi Again Andrew,

I generally go by what the lamp manfacturer recomended service life is,after that is a bonus,usually when the lamp starts to flicker indicates to me that its life is about over.With a 2000W shsc Osram i can expect round about 3000hrs before it starts to flicker.I have one here thats done 4450hrs and it is still giveing good light and still stable yet the other day I removed one that had 2500 hrs up and it was flickering badly.The rated service life for the 2000W lamp is 2000 hrs but you can get a lot more if you are lucky.A lot depends on the bulb and the power supply in your area.Ask Osram for a calculator which works out life you should expect I use one here as a guide.Yes Xenons are expensive but we cant afford these days to turn people away because of poor light on the screen as the cost of home cinema is getting affordable everyday.

Steve [Wink]