Film-Tech Forum ARCHIVE: Lamp damage

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Posted by Antonio Marcheselli (Member # 373) on 03-21-2001, 06:29 PM:

Hello everyone.

Today I've changed one of my mirrors in our Cinemeccanica V5.
I found, for the second time, that the lamp has a "spot" on the anode (is it the anode? the bigger part). It is a little piece of metal that is "growed" on the anode itself. On my previous lamp (Osram 2500W horizontal)a piece of metal "growed" on one side of the anode causing oscillation in the light beam. This time this "spot" is in the middle of the anod and all seems to be ok but I think that it is not normal.
Could be a rectifier problem? Should I have to replace all diodes?

I appreciate any suggestion you can offer!!

Thanks
Antonio

Posted by Darryl Spicer (Member # 711) on 03-21-2001, 06:37 PM:

If the spot is in the front middle where the energy crosses this is normal. To prevent this from getting worse like the previous bulb you need to rotate it a Quarter turn every 500 hours.

Does the cathode maintain its point or do you see cracks in it? This is the small one. The anode is the large one.

Posted by Paul G. Thompson (Member # 655) on 03-22-2001, 12:07 AM:

I know this is a strange question, but does it look like a ding ball? ( I am not an expert on ding balls...) The Xenon bulb may be operating out of parameters. If not, the only anodes I have seen with a ball forming on the anode was caused, in part, by poor filtering of the AC ripple.

Posted by Darryl Spicer (Member # 711) on 03-22-2001, 02:06 AM:

Paul

Cracks in the cathode can develope off this too can't it?

Posted by Paul G. Thompson (Member # 655) on 03-22-2001, 12:15 PM:

Darryl, I have seen the cathodes erode very badly, where the tip gets real blunt. But in all honesty, I have never seen one crack.

I have, however, heard that a re-design of the cathode may have happened, where the cathode was purposely manufactured with a split in it. Supposedly, the modification was made to increase the bulb life. Whether it was ever incorporated in ORC bulbs, I don't know.

Sorry, that is the best information I have.

Posted by John Pytlak (Member # 331) on 03-22-2001, 03:40 PM:

As I recall, prematurely eroded electrodes and growth of metal deposits on the electrodes may indicate unacceptably high AC current ripple in the DC supplied to the lamp. One of the lamp manufacturers (Osram?) had a pictorial guide to different problems and their effect on lamp appearance.

------------------
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 Leo Enticknap (Member # 534) on 03-22-2001, 07:22 PM:

Antonio - is it a Zenith X-2000 lamphouse?

We had a similar problem with ours - overheating, progressively worsening anode pitting and then a flicker. In one case a lamp exploded as I was removing it for disposal after only 950 hours (it had been rotated at 500).

At first we believed that the intake fan wasn't pushing enough cold air in and added another one, but that didn't cure the problem. After much scratching of heads and quite by accident, one of my colleagues eventually found what was causing it. The DC shunts on the power supply to the lamphouse ammeters were of the wrong rating, resulting in the meters giving a false reading. The shunts in the lamphouse were 60mA, but the ammeter was rated at 75. So we were over-running the lamps without knowing it.

According to the parts catalogue, all Cinemeccanica meters and shunts are 60mA. But they're all imported from Italy, and equivalents are impossible to get from UK suppliers. 75mA appears to be the standard in Britain. I guess what happened was that the original meter failed at some stage, and was replaced by someone who did not know to check the shunt rating on the supply feeding it.

Anyway, ever since we replaced the shunt with a 75mA one to match the meter, we've had no problems with overheating lamps.

Posted by Gordon McLeod (Member # 33) on 03-22-2001, 08:56 PM:

Also cinemecanica uses IREM rectifiers and there filtering and inrush current leaves much to be desired.

Posted by Randy Stankey (Member # 64) on 03-22-2001, 11:24 PM:

Do you mean like THIS?

When this lamp was taken out it had 6500 hours on it! ...and people were wondering why the picture was dim!

Sometimes you'll see the surface of the anode get rough and "pimply". The cathode will get rounded off as well. Of course this is an extreme example but a CERTAIN amount of this is normal.

I'd say to check your current and change your tap settings if needed. Also check for ripple like other people have said.

Posted by Antonio Marcheselli (Member # 373) on 03-23-2001, 08:28 AM:

Randy,

ARGH! No, nothing like that!!! I have an old 3000 hours lamp (I'm a projectionist since only 2 years and I haven't saw others old lamps!) and it seems so better than yours!!!
No, my "spot" is nothing compared with your photo. I will shot an image of the lamp and i'll post here.
Leo: no, are Zenith X4000. However, since I'm in Italy, perhaps shunts should not be a problem here!!!
And, Gordon, Yes, we use IREM rectifier.

I will post a photo soon.

Thanks to everyone!
Antonio

Posted by Neil Fish (Member # 698) on 03-23-2001, 08:15 PM:

Antonio- The symptom you describe sounds like a classic high inrush current problem. Have the filter capacitor tested. BTW- If this is an Osram bulb they will analyze it for you and give you a diagnosis of the likely problem. Also, as John mentioned, Osram does put out a book with photographs of various lamp maladies and their causes. I find it very helpful in diagnosing xenon system problems.

Posted by Stefan Scholz (Member # 147) on 03-24-2001, 04:38 AM:

To answer Leo's shunt item,

Continental ammeter shunt value has been 60 mV (Constant Voltage) full scale for a long time since the 1910's. Later, with international standardisation, in the 90's, it tended to change to 1 mA full scale, giving 75 mV for 75 Amp meter, 35 mV for 150 Amp meter. With Italien projectors of different make, sometimes older meters and newer shunts (and vice versa) were mixed in transition, so the setup tech had to check the combination when delivering the projector. (As you know, they always had apologies for "bad quality", and promised to do better "next time".)
Even today theese 60 mV shunts are still available on request, as are the meters. Any new stuff in cataloges is 1 mA.

Posted by Antonio Marcheselli (Member # 373) on 03-24-2001, 06:59 AM:

Neil,

Where this book can be found?

Thanks
Antonio

Posted by Gordon McLeod (Member # 33) on 03-24-2001, 02:53 PM:

Irem rectifiers (3 phase) typically have fairly small filter caps so inrush is usually not a big problem compared to the amount of ripple

Posted by John Walsh (Member # 168) on 03-24-2001, 03:33 PM:

The book is: "XBO Theatre Lamps - Technology and applications" avaiable from Osram.

It would be a good book to include in the download page, but there are a few good quality B&W photos that might not scan/pdf well.

Posted by Leo Enticknap (Member # 534) on 03-24-2001, 03:42 PM:

Stefan -

Many thanks for the explanation. Our projectors were installed second-hand and reconditioned, so as I say, I think the most likely explanation is that the ammeter installed in the lamphouse when new went bust at some stage and was replaced by someone who didn't know that there was any difference and just thought that an ammeter was an ammeter, full stop.

When we discovered the problem we looked in three electronics catalogues (big, major suppliers) and none supplied a 60mV meter. So we had to fit new shunts and meters to ensure that both were of the same rating.

Posted by Paul G. Thompson (Member # 655) on 03-24-2001, 04:52 PM:

Hi Randy

By looking at that bulb with 6000 hours, I would recommend a power supply filter check, as well as the power supply operating parameter check, be performed as you suggested. Since all three bumps are the same size, I doubt if there is a diode problem.

Three phase AC ripple got into that thing, and by observing how severe the bumps look, the problem developed over a long period of time.

Posted by John Pytlak (Member # 331) on 03-24-2001, 07:45 PM:

Paul:

Please tell us how three phase ripple would cause three mushroom growths, as seen in Randy's photo. Does the plasma ball move around in sync with the phases, perhaps by magnetic force? Interesting phenomenon.

Posted by Paul G. Thompson (Member # 655) on 03-24-2001, 08:10 PM:

Hi John,

I honestly don't know. It is an interesting phenomenon. All I know is it does happen. The bumps are 120 degrees apart.

I have seen this happen with bulbs used with single phase phase power supplies, also, but they leave 2 bumps 180 degrees from each other.

The three phase problems seem to cure themselves if the filter capacitors are renewed, or if the power supply is tapped for a lower current setting.

The phenomenum you are addressing happens quite frequently in the XPS-20-03 ORC power supplies operating at maximum rated output. Apparently, the capacitors are not large enough in capacity to do adequate filtering within that parameter.

Posted by Randy Stankey (Member # 64) on 03-24-2001, 08:10 PM:

This is the first and only lamp I have ever seen that had been left in this long. (Just for reference it was a Christie 3K lamp burning in a Christie 3K console.) There have been no problems like this in the past and the lamp has been running fine ever since. I'm pretty sure this happened because of the extreme age of the lamp and because we burn them at pretty close to the maximum limits. The reason the lamp was left in so long is that the person who wrote the log book entry had CRUMMY handwriting. All the people who came after him misread the entry and thought it was OK. We found it on a PM visit.

Normally we change them out at about 1800 hours, more or less. I have let them go up to 2000 in a pinch. (When the new lamps are on backorder, etc.) When we found this one I took one look and said, "What in the blankety-blank is this? I took this picture for my "Hall of Shame"... examples of things that you shouldn't do. I was going to post it a while back but I hesitated because I didn't want to be accused of "putting people down". The only reason I posted it now is because it was topical.

Needless to say, "The names have been changed to protect the innocent..."

Posted by John Pytlak (Member # 331) on 03-25-2001, 06:49 AM:

Randy:
Your policy of changing out a 3K lamp at about 1800 hours is a good one. That 6500 hour lamp was a bomb waiting to explode!

Not to mention the dim and flickering light it likely was producing.

Posted by Randy Stankey (Member # 64) on 03-25-2001, 03:21 PM:

I'm usually not a termpermental person but when I saw this I just about hit the ceiling.
We put the new lamp in and fired it up. Perfect. Then the guy said to me, "I was WONDERING why this one was dim..." I just bit my tongue and said, "Now you know, don't you!"

I had another place that kept telling me that the lamp wouldn't strike-up until about the 10th "crack". I kept telling them to change the lamp. They kept saying, "No, that isn't it." 3 or 4 times they call me up over a 3-4 month period with the same complaint and I kept telling them to change it. They never did.
I was there on a PM visit and they told me the same story. My answer was, "Go get your mask and gloves." By the time he found them I had the lamphouse undone (to the point of needing the mask and gloves.) I made HIM change the lamp while I watched. 10 minutes later we strike it up... WOW! It worked! I wonder how come?

Turns out that lamp was almost 4,000 hours old!
Every time I say to myself, "Now, I've seen everyting!" I turn around and there's something else!
After about 2-3 months of this kind of junk NOTHING pisses me off anymore.

When I go to these places, first thing I do after finding this kind of junk is take them outside and throw the lamp into the dumpster really hard. Then I tell them, "This is what'll happen if you don't change lamps when you're supposed to!" (The dumpster adds a nice "reverb" effect that helps punctuate the point. )
Most people are surprised to find out just how dangerous these things really are!

Posted by Paul G. Thompson (Member # 655) on 03-25-2001, 03:37 PM:

Hi, Randy

As a reminder, xenon lamps should be smashed before they are disposed of.

Never throw away an intact xenon bulb. Some airhead dumpster diver may pull it out of the trash and say, "This is neat", not knowing how dangerous they are. If that thing blows up in their faces, the theater could be held liable.

Posted by Randy Stankey (Member # 64) on 03-25-2001, 03:58 PM:

I always tell people to put them back in the box and wrap them up in a trash bag, them toss them on the floor really hard. I usually say something like "It's illegal to throw hazardous material in the dumpster... unexploded lamps are considered Haz-Mat..." (I don't think lamps are really Haz-Mat but if you don't exagerate people won't get your message sometimes.) When they are busted inside the box, the "clamshell" contains most of the force. The cardboard and layers of garbage bag contains the rest. It makes hardly any sound compared to the "amplified" sound of the dumpster. It makes a really good demonstration so that people realize just what kind of power they are toying around with. Most people come away a little bit "scared". I find that I have to say things about 10 times louder and make things about 10 times more "graphic" or else people just don't hear the message.

PS: Who's going to make a video of a xenon lamp exploding?
I was thinking of taking a lamp way the hell out back in the woods, setting it up on a stump or something. Then hang an old T-shirt up about 2 feet away from it and step back about 50 yards to take pot-shots at it with a .22 rifle. I've done this once or twice before. It makes a spectacular "show". If I had a video cam I'd do it but alas, I'm too poor. What would be even cooler if we could get some super slo-mo shots of the pieces of glass hitting the T-shirt. Then you can show the video to people and say, "If the schrapnel can penetrate a piece of cloth, just think about how it would penetrate skin!"

Posted by Brad Miller (Member # 2) on 03-25-2001, 04:13 PM:

I believe Joe is working on a video of "what to do with those leftover xenon lamps". It shows him in his car driving on the highway and tossing naked lamps at drivers that cut him off. Lots of car wrecks, violence and death. Just the kind of movie that sells!

Posted by Randy Stankey (Member # 64) on 03-25-2001, 05:05 PM:

I want to mount one of those babies in the front grille of my car and hook it up to the high beam switch! The car would probably stall the moment you hit the swtich due to the electrical drain.

Posted by Antonio Marcheselli (Member # 373) on 03-25-2001, 05:15 PM:

Few months ago I had an used lamp in my hands. My manager told me to buy mask and gloves immediately because he discovered that pressure in a xenon lamp is very high also when cold.
So I've opened the OSRAM paper, and read about disposal.
I've put the lamp in its bag, in its box, in a plastic cover and I left the lamp fall into the floor from 2 meter high.
From that time I'm very afraid when I have to rotate a lamp or simply go around to a lamp not closed in a lamphouse...

Bye
A

Posted by Paul G. Thompson (Member # 655) on 03-25-2001, 05:37 PM:

It is my understanding the pressure in the bulb at room temperature is about 125 pounds per square inch. When the bulb reaches operating temperature, the pressure is about 450 pounds per square inch.

It should always be handled with caution and common sense.

Never assume anything.

Most accidents happen out of carelessness, and not paying close attention to what you are doing.

Posted by Joe Redifer (Member # 3) on 03-25-2001, 06:24 PM:

Brad, Randy-

Actually I was going to make a fictional movie where someone calls the theater with a "Xenon bulb threat" (as opposed to a bomb threat) and the whole theater is quickly evacuated. The manager does not meet the callers demands so they decide to blow up the xenon bulb which they have hidden in the theater. The entire complex explodes sky high in a sequence that makes the building explosion in Terminator 2 look like a firecracker.

It could happen!

Posted by Randy Stankey (Member # 64) on 03-25-2001, 07:43 PM:

It is my understanding that there is about 10 atmospheres of pressure inside a cold xenon lamp. The average air pressure at sea level is 14.7 psi. That means there is approximately 147 pounds of pressure in a cold bulb. When it gets hot, of course the pressure goes up.

If you use the Ideal Gas Law: PV=NRT

P= Pressure
V = Volume
N = Amount of gas (in moles)
R = Ideal Gas Constant
T = Temperature (Degrees Kelvin)

Now we can cancel out V, N and R because we are not changing them. (The amount of gas and the volume of the bulb are the same.) We are left with P and T. We can just make them into a ratio.

P at room temperature is 147 pounds and we know that room temperature is 295 degrees K. If the lamp goes up to 300 deg. C when it is hot that would be 573 deg. K.
573 / 295 = 1.94

Multiply the "cold"pressure by 1.94...
147 * 1.94 = 228.92

The answer is that a xenon lamp has more than 200 pounds pressure in it when it's hot.
Of course if the lamp gets hotter than that the pressure would be more but the theory is the same, just plug in different numbers.

What I ask people is, "How would you like a piece of razor sharp glass hitting you in the face with 200 pounds of force?"

(If my math is off or if my theories don't hold please correct me.)

Posted by Paul G. Thompson (Member # 655) on 03-25-2001, 07:55 PM:

Randy, my reference is what the Osram guys told me about 20 years ago...

Posted by Randy Stankey (Member # 64) on 03-25-2001, 09:27 PM:

The only information I have is the "ten atmospheres factoid". The rest is calculated from the gas law.

If the lamp temp. went up to 400 deg. celsius then the pressure would go up to 335.36 psi.

I guess the answer would be for somebody to take one of those infrared thermometers and take a reading off a lamp that's just been turned off from running a show. That would give a pretty close estimate of the real temperature. If we could find out the actual cold pressure inside the lamp as well, then we could calculate the real pressure.

Even if my calculations aren't quite right, I know they are in the ballpark. It's still good enough to get the point across to the "popper jockeys".

Posted by Toby Dobson (Member # 771) on 03-26-2001, 07:10 AM:

I have lurked here for a while now and would like to say hello to all. I have used both Christie and ORC bulbs in both Christie and Highlight II lamp houses. I have had christie bulbs mushroom out like Randy's a few times before, but not near that bad! They will be fine one day, three days later, they have the three pimples on them. this always seemed to happen rather quick. This also never happened with ORC, it will with extended use or current problems, but never consistently at the end of it's recommended life.

Posted by Bruce McGee (Member # 131) on 03-26-2001, 09:31 AM:

How about impurities in the metal being used in the lamp?

My xenon knowledge is limited to the 350 watt Ushio lamps that my Eiki 16's use. But, recently, I was able to repair the power supply (shorted diode) after reading a post here at FT.

I've had lots of TV/Radio repair experience. I would not advise doing anything otherwise. You could get hurt.

Posted by Darryl Spicer (Member # 711) on 03-26-2001, 10:56 AM:

Randy, Your theories are pretty accurate. Depending on the internal tempreture of the xenon gas will determin how much preasure is on the bulb. Internal preasure can get as high as three times the preasure as when it is cold.

During manufacturing the bulb is put thru stress tests. The xenon gases are added thru the same tube the glass blower uses to form the bulb. The bulb is then cooled to a state that freezes the xenon gases into crystals. The glass blower is then able to seal off and remove the blow tube. That is why there is a nipple on the bulb. The bulb then is allowed to warm back up to room tempreture. Everything is tested at maximum for a short period of time before it is passed on to shipping.

Posted by John Pytlak (Member # 331) on 03-26-2001, 11:03 AM:

I recall that NASA did have a training film on the proper handling of xenon lamps that did show lamps exploding in slow motion. These lamps can be just about as lethal as a hand grenade.

Here again is the link to the NASA safety manual on proper handling of xenon lamps:
http://osat.grc.nasa.gov/GSM/GSM-26.htm

Posted by Randy Stankey (Member # 64) on 03-26-2001, 11:52 AM:

One of my old college buddies used to be a lab assistant for Dr. Edgerton in the Strobe Lab at MIT. In the summer during heir "IAP Session" they have a courst in super-slo-mo photography. I always wanted to take an old lamp there and have pictures taken of one exploding. It would be cool!

PS: Doc Edgerton is the guy who took those stop-motion pictures of a bullet in flight, etc. If you've ever seen the one of the drop of milk shooting up like a fountain, that's one of his too. I met him once. He was a pretty cool guy. Even by MIT standards.

Posted by John Pytlak (Member # 331) on 03-26-2001, 12:08 PM:

Harold E. Edgerton was the "founding father" of high speed photography and super slow motion, and is on the SMPTE "Honor Roll" of distinguished pioneers in motion-picture technology:
http://web.mit.edu/edgerton/main.html
http://www.hamilton.net/Aurora/City/edger7.htm
http://web.mit.edu/newsoffice/tt/1998/sep23/edgerton.html
http://salticus-peckhamae.mit.edu/afs/athena.mit.edu/org/m/museum/exhibits/doc2.html

Posted by Evans A Criswell (Member # 381) on 03-26-2001, 01:35 PM:

Somewhere at home, I have a videotape of a 1 hour show about Edgerton that I taped off PBS back in 1987. I'd love to have a better copy of that with better picture quality (I lived 100 miles from any major city at the time and reception wasn't great). The name of the show was something like "Edgerton and his incredible seeing machines" and it may have been a "Nova" show, but I'm not sure.

Posted by John Walsh (Member # 168) on 03-26-2001, 02:30 PM:

If it's the Edgerton documentary I saw, it was pretty good. It showed him in front of a class, demonstrating a huge strobe lamp. The lamp was used for taking military aerial reconnaissance photos at night. He held a newspaper up in front of the strobe lamp and fired off one flash. The lamp was so powerful, that even with only a 1/10 sec flash, the newspaper caught fire.

Man, there is a lotta cool stuff in this world.....

Posted by Greg Mueller (Member # 17) on 03-26-2001, 02:52 PM:

"The lamp was so powerful, that even with only a 1/10 sec flash,the newspaper caught fire."

Good Lord!
What kind of electronics did he use to juice it with? What kind of lamp?

------------------
Greg Mueller
Amateur Astronomer, Machinist, Filmnut

Posted by John Walsh (Member # 168) on 03-26-2001, 03:12 PM:

They didn't say what electronics were used. If I remember, he was expaining that this lamp was used for the military during WW2, yet the documentary was shot much later. So, even though this bulb was that powerful, it was something like 30 year-old techonolgy.

The bulb was in a reflector- about the same size as a 4000 watt film lamphouse reflector. The newspaper was taped to a yardstick, held about 1 foot in front. I imagine the black printing on the paper helped it ignite. It was weird how there was a slight delay after the light went off... then the newspaper burst into flames.