Film-Tech Forum ARCHIVE: when to change a xenon lamp

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Posted by Carl King (Member # 398) on 11-16-2000, 12:23 PM:

I was curious about how many hours most of the working projectionists get out of a xenon lamp before changing it. In my multiplex I use 4 vertically mounted 1600W and 3 horizontally mounted 2000W lamps. The horizontal lamps get rotated 180 degrees every 250 hrs. Around 3000 hours the light on the screen is noticably less and the lamps get changed. Osram reccommends rotation at half-life I believe. The vertically mounted lamps do not get rotated.

Carl King

Posted by Ian Price (Member # 14) on 11-16-2000, 12:56 PM:

I have two sizes of Xenon lamps.

Christie CXL20 (I think I will get 30% - 50% over guarentee.) Guarentee is about 2,400 hours

Christie CXL30SC (I get about 60% of guarentee before flicker causes me to change the lamp.) Guarentee is 1,440 hours.

Posted by John Pytlak (Member # 331) on 11-16-2000, 03:01 PM:

The warranteed hours should be used as a guideline to the expected life. Going much beyond (e.g., 2X) the warranteed life greatly increases the risk of catastrophic lamp explosion, lamphouse damage or personal injury.

Many factors affect lamp life: brand of lamp, lamphouse design, cooling, current ripple, proper lamp rotation, integrity of connections, etc. Change lamps when ignition becomes unreliable, flicker becomes noticable, there is significant lamp blackening, or proper screen luminance and uniformity cannot be maintained (Standard SMPTE 196 has an aim of 16 footlamberts). Inspect the electrodes and seals for signs of excess electrode heating, impending seal failure, or vitrification (crystallization) of the quartz.

------------------
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 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Posted by Frank Prete (Member # 627) on 11-16-2000, 06:58 PM:

If you hear a loud bang from your lamphouse, notice glass all around the base of the lamphouse and the lamp won't strike anymore, then it is probably a good time to change the lamp!

I have seen some lamps get huge hours. I personally changed on that had done ~7500hours. One lamp i know of was installed in 1985 and removed when the theatre renovated late 1996, accumulating some 17,000 hours. On the other hand, I have recently seen lamps fail completly (bang!) after only a few hundred hours.

A good idea is to keep a log of the hours that the lamps in your lamphouses do. If you consistently see that a lamp in cinema 3 (for example) is only doing 1200 hours, and all others are doing 2400 hours, then maybe there is some investigating that needs to be done.

And remember to wear a safety suit of some sort when handling lamps. At bear minimum a face sheild, heavy jacket and heavy gloves should help.

Posted by Rick Long (Member # 213) on 11-16-2000, 09:27 PM:

Frank is right, of course, but I find the heavy gloves a hinderance. Makes it difficult to determine when the cathode clamp screw is tight enough, or about to strip its threads.

Posted by Carl King (Member # 398) on 11-17-2000, 12:56 PM:

Thanks to all for the advice. Safety is, of course, paramount when handling Xenon lamps. I use a welders thick suede jacket as well as gloves and face shield. The gloves ar awkward so I usually on use one on the hand that is sliding the lamps into position.

Mr. Pytlak, I love the articles you write for Kodak Cinema Notes. I use them for training new operators (as well as educating myself).

Thanks again, everyone

Posted by Mike Spaeth (Member # 524) on 11-18-2000, 04:29 AM:

Our policy is, quite simply, warranty + 25%

Posted by Steve Guttag (Member # 268) on 11-18-2000, 06:10 PM:

Ian,

On your CXL-30SC...what type of rectifier are you using? By any chance is it either an IREM or Kneisley? In any case, please list the model.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Ian Price (Member # 14) on 11-18-2000, 07:20 PM:

Our CXL30SC is in our large house. It resides in a Strong Super Highlight console. The switcher power supply may be the problem as it has lost some of its high current capacity. ie: It no longer auto-strikes the lamp. We must manualy strike the lamp each time. Also, if the lamp is turned off, it will not fire until 10 minutes have passed. It will not strike while it is hot.

Posted by John Eickhof (Member # 323) on 11-18-2000, 11:13 PM:

Ian, try replacing the filter capacitors in the switcher supply. It sounds like it is not storing a decent charge to ignite the lamp. Also, check the 'boost' voltage circuit, it sounds like the diode is burned open. Good
Luck! John

Posted by John Pytlak (Member # 331) on 11-20-2000, 07:11 AM:

Carl King said: "Mr. Pytlak, I love the articles you write for Kodak Cinema Notes. I use them for training new operators (as well as educating myself)."

Thank you.

I miss my days in the booth, but enjoy Kodak's support in helping theatres "Do Film Right". If I stray from offering practical and realistic advice, or make a misstatement, please let me know. Sometimes the view from "the film factory" may not mesh with what works best in the theatre. I'm willing to listen and learn too.

Posted by Jerry Chase (Member # 660) on 11-20-2000, 07:51 AM:

>"If I stray from offering practical and realistic advice, or make a misstatement, please let me know. Sometimes the view from "the film factory" may not mesh with what works best in the theatre. I'm willing to listen and learn too."

That one paragraph puts you a cut above your peers, and earns you the respect of all the people in the trenches. I offer a heartfelt "Thank-you, sir."

Posted by Pat Moore (Member # 380) on 11-21-2000, 09:10 AM:

Ian;

I'd be surprised if it's the Switcher that's causing the slow or no strike problem in the Strong system. Is the open circuit voltage getting to 120V or higher? If so, the Switcher is doing its job.

If the lamp does not even get pulsed by the igniter and the open circuit voltage is correct, then it's the circuit that fires the igniter that's at fault.

It sounds like you have the AC Igniter in these systems and the firing board is separate from the igniter itself. Check connections and the firing relay in the socket -- those will corrode over time and might cause the problem you describe.

If it's the DC Igniter, the circuit board in the igniter can pretty easily be replaced or upgraded. There's a Service Bulletin on our website on that:
http://www.strong-cinema.com/SB-0019.pdf

Pat

Posted by Leo Enticknap (Member # 534) on 12-04-2000, 07:47 PM:

My rule with xenons is to run them as long as you can but to stop when the picture quality goes below what paying customers have a right to expect. Just when that point comes depends on all the factors that John P mentioned earlier. But the important point I'd stress is not to keep on running a dim or flickery lamp in the hope of saving a few quid/bucks, because your customers (if they have any sense) will think "this picture's bad, I'm going somewhere else."

I use 2k horizontal lamps in all 5 projectors here. After a fair bit of trial and error getting the running current, ventilation and rotation intervals right, we seem to be getting 3,000 good hours out of each one. That means anode pitting, envelope blackening and a flicker start to directly affect the picture quality after 3,000 hours.

That's 2x warranty, which is pretty much what I'd expect - I've heard it said that manufacturers generally guarantee something for about half the use they realistically expect it to get - they don't want to be constantly paying out under warranties, so they build in that safeguard.

The way I approach this issue is common sense - don't throw away a lamp which has gone over its warrantied hours but is still giving a perfectly good picture, but don't let things get to the point where presentation quality suffers.

Posted by Gordon McLeod (Member # 33) on 12-05-2000, 07:56 AM:

My rule of thumb is 20-25% over warranty
The warranty is based on a predicted failure rate of half a production batch.
Each manufacturer has there bell curve looking different of where the mortality peaks. At the end of the lamps life two things that don't effect the direct presentation start to occur physically in the lamp. This is the weekening of the quartz itself due to the exposure to UltraViolet light (devitrification) This increases the risk of catastrophic failure(big bang theory) . The increase in risk is not directly proportional to the number of hours over warranty that you go.
The other area is the seals which are either foil or graded glass. Over time these also weaken. Refunding a complete friday night preformance is usually more expensive (not counting customer bad feelings) than the small cost of the lamp hours.
If a lamp is actually thrown out at the warranty point most still cost less to run per show than half of one patrons admission

Posted by Rory Burke (Member # 512) on 12-05-2000, 08:22 AM:

Warranty hours? bulb condition? flicker? what is that? hahaha! That is the way unfortunately a theater chain east LA does business. They change bulbs when they abosolutely have to and only if there are repeat complaints regarding the picture by customers. I had to change a bulb(i dont work there)at one location last summer during Gladiator (already a dark movie)because there were bright spots on the screen. it couldn't have been more than 2 ft/lamberts on the screen center if that. With no film the screen looked like the flat lense was taken out and you were trying to focus the bulb<no kidding> Unbelievable!!!!
I convinced the manager to let me change the bulb there. I never do or thought of just fixing it myself but since he said that his tech wouldn't come in and had been informed for weeks that he wouldn't say anything if I changed it. I know theater chains are suffering fiscally yet now it is reaching the customer and ruining their experience totally. Since then, I have refused to have to admit that all their screens are heading that way as well but darn it that some just is giving a d#$m!!!

Rory

Posted by Rory Burke (Member # 512) on 12-05-2000, 08:54 AM:

I have composed myself and wish to add that it is very refreshing that you folk out there in the film world, freezing cold booths in Ste Foy Canada, or turmoil stricken projectionists in Tel Aviv, Israel....our hermanos sweating in non air conditioned booths in the amazonian regions of south america,or the multilplexer servicing xxxx theater chain in Shopping Mall of America....it is good to know that there are those who care!!!

Rory

Posted by John Pytlak (Member # 331) on 12-05-2000, 09:11 AM:

Rory said: "it is good to know that there are those who care!!!"

I agree that most of us on Film-Tech really do care about presentation quality. Unfortunately, there are many theatres who don't seem to realize that poor presentation quality will drive audiences away. Audiences may not complain about poor presentation, but they won't come back again. "Film Done Right" is hard to beat. "Film Done Wrong" is a poor excuse for Digital Cinema or home theatre to take over (BTW, Digital Cinema will likely suffer from the same short-sighted cut-cost-to-the-bone mentality). It's penny-wise and pound-foolish to neglect maintenance.

Posted by Ari Nordström (Member # 288) on 12-07-2000, 02:59 PM:

My Xenon bulb policy is simple. Osram recommends around 1000 hours for the 4000 Watt bulbs we use so that's when I change them. Of course, since we're a changeover theatre I always replace both at the same time (which means that I go to extremes to make sure that they go past 1000 within minutes from each other...)

I've never used a bulb for more than 1200 hours anyway, and that was only because I had trouble getting new ones on time. Made me nervous. I'd rather just change the bulbs than have to vacuum lamphouses and install new and expensive mirrors.

Posted by Dustin Mitchell (Member # 372) on 12-07-2000, 10:37 PM:

Haven't had a bulb blow on us yet, but let me tell you, we must have gotten close. Just today I had one go out-wouldn't stay lit. Was a 1600 watter supposed to pull between 65 and 75 amps I think. When I checked the meter, it was pulling less than 45...

Let me tell you, once I get confident at changing bulbs, things are going to change around here.

In a related story, I managed to save that show in less than 10 minutes. Story to follow in another thread.

Posted by David Kilderry (Member # 142) on 12-08-2000, 03:18 AM:

Ari,

You can certainly get more life out of a 4k than 1,000 hours. You don't stop using your car after the warranty expires do you?

In most instances you can safely run for around 2,000 hours on a 4k in a modern well ventilated lamphouse. Recent lamphouses are so much more efficient than a 30 year old unit.

Most lamps will give sure signs that they are nearing the end of their life: flicker becomes evident, envelope can blacken, ignition takes more than one strike, light fall off etc.

Our circuit is over 1,500 screens, if I advocated changes on 4k's at 1,000 hours we would be out of business! Let me balance that by saying we work closely with both major quality xenon manufacturers to ensure we achieve maximum light quality and life without compromising our aim of 16 flicker free footlamberts or risk of explosion.

For the record we have had 6 explosions in recent years and all occurred within the lamp warranty hours. The explosions were caused by manufacturing faults. We operate xenons from 1,600 watts to 7,000 watts in almost every type of lamphouse: Kinoton, Cinemeccanica, Strong, Christie, Xebex, Bauer etc.

If the average screen operates for 5,000 hours per year, you can see how incredible the xenon lamp costs would become if we swapped at 1,000 hours regardless of lamp condition. Of course there are many variables in operating conditions: airflow, cold strikes/hot strikes, continuous operation, angle of lamp operation, amount of ripple from power supply, poor installation and handling, fluctuating local supply etc.

David Kilderry

Posted by Ari Nordström (Member # 288) on 12-11-2000, 03:47 PM:

David,

Yes, I know I can get more than 1000 hours from a 4k (as I wrote, I've gone to 1200, and 1100 is not that uncommon), but I've had enough of Xenon bulb explosions and mishaps to just order new bulbs in time. The warranty time of the Osram 4k's is much shorter than 1000 hours, btw. I think it's around 250 or 300 hours. I'd never go to 2000 hours with either our present lamphouses or our present rectifiers. I know my predecessors did, but they had a lot more explosions than I have.

Our lamphouses are about 30 years old (Cinemeccanica Zenith 4000; not great but mostly they do what they're supposed to), and so cooling could probably be better. I know it could be better, btw; the aux mirrors are a bit too easily burned. I guess I could try to locate a newer model but from what I gather, most of the new 4k lamphouses available today hold horizontal bulbs, something I never much cared for. And I doubt management would give me the new lamphouses right now; we have other worries right now.

Also, we run the bulbs at around 130A which also adds up. They'd probably take another 200 hours at 120A, but we wouldn't get the kind of light we need.

When a bulb blows, replacing the main mirror is VERY costly. The aux mirror is not free, either, but it doesn't cause a heart attack when you tell the manager how much a new one will cost.

Another thing is that I've found that after a 1000 hours, the light is just not as good as it could or should be. If we're running 70mm it's almost unacceptable (another monetary question, really; we could by new 70mm lenses but they cost a LOT and we don't run 70mm that often so...) Around 1000 hours, Scope also begins to suffer, and that's a shame. Don't get me wrong; I check the light often enough, and adjust it as soon as there is any reason to, but the lamphouse is too small and the screen too big...

So would I continue using a car after its warranty's expired? Absolutely, and I do. But a period equalling four times that warranty period? Would I continue using the car for longer trips where I would have to really rely on it, really count on it, no matter how far I'd have to go or who'd ride with me? Would I continue using that car if I noticed new puddles of oil and water below it on the parking lot every time I had to leave for yet another journey?

I don't think so. Unless somebody gave me enough money to buy a better car.

Posted by Ari Nordström (Member # 288) on 12-11-2000, 04:24 PM:

Just thought of another side to this:

Those precious few times I work at the local multiplex, I really couldn't care less about how long they've had a bulb in any given lamphouse. I know they often go past 10 000 hours using 1.6 k's. The 1 k's go...well, I don't even dare to guess.

Do I worry about an explosion? No, not really. There's an aluminum mirror that simply won't break, and there aren't any aux mirrors you should worry about. It takes five or ten minutes, tops, to replace a bulb and get the show running again. A 1 or 1.6k bulb costs a fraction of what a 4k costs, and I don't have to think about their budget. Why should I worry? Most of the time, a bulb will blacken to the point of being unusable before exploding anyway, so why should I worry?

(Just so you know, the owners of this particular multiplex have made it abundantly clear that their projectionists are not expected to worry about these things; they use fancy word when talking about presentation in public, but they fail miserably at floor level.)

Posted by David Kilderry (Member # 142) on 12-12-2000, 04:17 AM:

Ari,

I know the Cinemeccanica Zenith lamphouses well. They were probably one of the most efficient verticle lamphouses around but cannot compare to the efficiency for light and cooling of a moderm horizontal unit.

You know your xenon environment better than I do and the rectifier has a lot to do with it. We ran 5,000watts in our Zenith lamphouses and always got around 2,000 hours. You will find the warranty for a 4k or 5k for most manufacturers is above 500 hours.

We run 4k and 5 k lamps in Kinoton and Cinemmeccanica Vic 5 lamphouses with no problems of quality flicker free light at well over 2,500 hours in most instances. If you are really concerned at running lamps over 1,000 hours have an air-flow check of the Zenith and check how much AC your rectifier is not correcting. If you can find just 500 more hours you will have big savings on your theatres number one consumable cost.

I have never known a steel mirror to withstand more than one or two explosions without the mirrored surface being effected to the point where it drastically restricts screen brightness. An efficent cold light mirror may dissappear in a bang but lets much more heat pass through it instead of forwards onto your film and gate.

David