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Topic: Lamps for changeovers: Leave 'em on or off?

Jim Bedford
Jedi Master Film Handler

Posts: 597
From: Telluride, CO, USA (733 mi. WNW of Rockwall, TX but it seems much, much longer)
Registered: Jun 99

posted 07-10-2000 10:16 AM

We do changeovers on Brenkerts (that are older than most of Film-Tech readers) at the Nugget in Telluride. Remember when that was done everywhere? So here's the question.

Upon striking the lamp, should it be turned off at the end of each reel change or left on the entire show? Issues: Cost of electricity; shortened hours of usable bulb life; does striking take more life off the bulb than leaving it on; projectionist preference; heat in booth during summer; too much ambient alien light flooding the booth; ozone production; etc.

I have heard both sides from dozens of techies and projectionist and well meaning opinionators. Are there still dueling opinions or one preferred way to do this?

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 07-10-2000 11:39 AM

I think this has been discussed in another thread. The "rule of thumb" is that each lamp ignition takes about 20 minutes off the life of the lamp. So probably not worth turning off for 2000-foot reels, but beneficial for longer reels.

Any "official" word from xenon lamp manufacturers lurking out there?

------------------
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

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 07-10-2000 12:12 PM

The rule of thumb from Osram was 1 hour per ignition depending on the inrush current and the violence of the ignitor
In fact they still ask for # of ignitons on warranty claims
I always tell operators as follows 2000' or 4000' reels leave them on
6000' reels turn them off
All lamps are ozone free so that is not an issue but the ignitor produces ozone during ignition so more ignitions = more ozone

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 07-10-2000 01:38 PM

I now fill in at both a single-screen with carbons and a multiplex with full automation, but when I was working in a single with xenons, I did pretty much what everyone else is suggesting--leave on for small reels and turn off between large (60-minute) reels. The only exceptions would be when the lamps were getting toward the end of their useful lives and for "important" shows (sold-out house, etc.), in which cases I would leave both lamps struck for the entire show, regardless of reel size, due to fear of having to stop the show for a reel change in the event of a bulb explosion upon being struck.

As Brad mentioned in another thread, be sure to close the hand dowser between reels. Otherwise, you'll damage the fire shutters and/or melt the changeover blades. I had a less-than intelligent co-worker who melted a changeover blade while I was on vacation. It stayed stuck in a half-open position until I returned. He couldn't figure out why the picture from that projector was so dim... (Ack...this is starting to bring back bad memories!)

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Travis Cape
Expert Film Handler

Posts: 122
From: St. Louis, MO, USA
Registered: May 2000

posted 07-10-2000 06:14 PM

Well I tried to leave the lamps lit last night in our non air conditioned booth. I made it to the third reel, until I was so hot that I didn't care about bulb life. I also felt sorry for the dowser and my new reflectors. I will try again when it gets cooler and see if I can do any better.

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 07-10-2000 07:12 PM

Yeah, I agree with everything that Scott said. I would only add that; at a few c/o houses I have worked at, the bulbs would make a noise in the sound system when ignited. If it is an "important" show (some one famous is in the theater, etc.) you might leave it on to avoid that "bzzt" or whatever sound it might make.

I tend to think if the lamphouse overheats while sitting with the dowser closed, it probably is just not being cooled enough. Some one might check the lamp wattage vs. the manufacturer's recommended cfm airflow- maybe ask the manufacturer about leaving the dowser open or closed. (I feel a lamphouse should be designed for leaving it closed.) I would not think that it matters whether the booth has AC in it or not since that only going to be a 40'F difference or so. Of course, cooler is better for both the lamp (and the operator!) but the 40'F difference seems small.

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David Johnson
Film Handler

Posts: 54
From: Melbourne Vict Australia
Registered: Oct 1999

posted 07-11-2000 02:18 AM

It is standard practice in our circuit (and common in most Australian circuits) to reduce the lamp current to around 20 to 30 amps when the lamp is not actually screening film. As we use only Xebex rectifiers this is quite simple, all that is required is to bridge out teminals C&D when the projector starts. The Xebex rectifers have separate standby and full current adjustments. Using this method we get long lamp life and eliminate any noise in the sound during ignition, as Ushio make Xebex rectifiers and Ushio bulbs I think it can be considered as an endorsement from the manufacture, we have been doing this for over 20 years now. As a point of interest a new 5KW bulb will stay alight on around 15 amps.
David

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David Kilderry
Master Film Handler

Posts: 355
From: Melbourne Australia
Registered: Sep 1999

posted 07-11-2000 04:20 AM

David,

You raise an interesting point. At our circuit - you know who we are - we have done a few experiments in the last few years.

We have trialled in various multiplexes:

Lamp on full all day.

Lamp dropping to low current as you do.

Lamp igniting at projector start and off at stop.

We have also trialled Osram, Ushio and ORC lamps in that time.

Our tests, although far from conclusive, showed none of the operating methods lead to substantially longer or shorter life.

What we did find is that 15 minute after show blower (extraction cooling on timer at end of night)is required.

Cinemeccanica Vic 5 console, Kinoton, Xebex and Strong LumeX lamphouses give the longest life (ahead of Strong X60C, X60D, Bauer U3, U4 and Christie).

Ushio lamps provide the longest life.

Rotation not required for most lamps.

Where poor lamp life was experienced it was almost always one of 3 things: poor ventilation, bad rectifier, poor quality lamp brand.

David

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David Johnson
Film Handler

Posts: 54
From: Melbourne Vict Australia
Registered: Oct 1999

posted 07-11-2000 06:55 AM

David,
I don't think I am aware of your circuit, do you have "The Boomerang theater Andamooka" "Civic Ashburton" and "Regal Hartwell"? You raise and interesting point, as you may recall we only use "Kinoton" "Xebex" and "Christie consoles" all use Xebex rectifiers, even the "Christie" have factory fitted "Xebex" rectifiers, and we have never made any tests as this is always the way we have done things, we also fit timers to the blowers to keep them running for 10 minutes or so after the bulb is turned off, (I think you may have got that idea from us) we are also convinced that this pays off, but we have never done any test to prove or disprove our theories, but at the worst it can do no harm if it don't do no good.
David

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 07-11-2000 09:12 AM

This is one of those topics where there seems to be no clear answers to the questions. We've done similar experiments as manufacturers noted above, as well as previous experience in circuits.
My experience with "standby power", for instance, is totally opposite what I read above. Standby operation still clocks the hour meter and seems to increase arc instability, thorium migration problems, etc.
If ignition noise is getting into sound systems, then there are some other problems to consider; that shouldn't happen.
The rules of thumb I've heard for life lost per ignition cycle vary from 20-minutes to one hour, but I think that's based on people's impressions and experience.
I have noted that lamps that consistently meet and surpass warranted hours are those ignited once per show in platter operations -- that leads me to think that fewer ignitions are better. But what's the use of gaining 20-minutes of life if that 20-minutes is wasted shining on a dowser?
Definitely agree on one thing -- for premier shows, those nights when you just CAN'T have a problem, get the lamps on and leave them on. Most problems seem to occur during the ignition cycle or soon afterwards.
Random thoughts from the midlands...

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Ian Price
Phenomenal Film Handler

Posts: 1714
From: Denver, CO
Registered: Jun 99

posted 07-11-2000 06:26 PM

Jim, I think we turned the lamps off at the Nugget because of ventalation and overheating problems. I know they leave them on at The Max. I turned them off at Minnie just because it's what I am used to. The Masons turns theirs off because of heat and power issues.

By the way I thought the lamps at the Nugget needed to be replaced in May, so work that into the Festival Budget.

Large

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David Johnson
Film Handler

Posts: 54
From: Melbourne Vict Australia
Registered: Oct 1999

posted 07-12-2000 01:30 AM

Pat, I tend to agree with what you say about the lamp hours waisted in standby and also the rule of thumb about loss of lamp life due to striking the arc, no one can say for sure what the effect is on lamp life. As you observed the best lamp life is when the lamp is struck once for a feature, but when you consider the turn around time between sessions now is quite short it makes good sense to leave them in standby for the short duration and thus prevent exessive striking.
David

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 07-12-2000 09:53 AM

True, David. It depends on intermission times in single projector systems, should have mentioned that. I seldom see a turnover time of less than 15 minutes in most places today, though.

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Christopher Seo
Jedi Master Film Handler

Posts: 530
From: Los Angeles, CA
Registered: Jun 99

posted 07-12-2000 03:58 PM

About having a standby current for lamps, I thought that the manufacturer (well, at least OSRAM) specifically says never to operate the lamp lower than its rated current and that this will not increase bulb life. Are the problems that result from doing this what Pat mentioned?

Also, how long are hand dowsers designed to be closed? I believe the Xetron lamphouse has a warning saying it should not be closed over 5 minutes with the lamp on, or is this just an ultra-cautious warning?

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 07-12-2000 08:09 PM

It's interesting that someone brought up the idea of running lamps at a lower "standby" current. With older Christie rectifiers, this isn't possible, since adjusting the rectifier requires killing the lamp. Oddly, though, the Eik EX-6100 16mm projectors that I've used are designed to do this--they take 1kw lamps that normally run at about 50 amps. After you strike the lamp, though, the current drops down to about 30 amps until you start the motor. These aren't my favorite projectors (great pix and sound, but they feel really cheap), but I always thought that this was kind of a neat feature, though I'd be interested to know if this actually does save the bulb life.

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