This is topic Lamps for changeovers: Leave 'em on or off? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Jim Bedford (Member # 4) on 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?
Posted by John Pytlak (Member # 331) on 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?
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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
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Posted by Gordon McLeod (Member # 33) on 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
Posted by Scott Norwood (Member # 30) on 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!)
Posted by Travis Cape (Member # 466) on 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.
Posted by John Walsh (Member # 168) on 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.
Posted by David Johnson (Member # 173) on 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
Posted by David Kilderry (Member # 142) on 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
Posted by David Johnson (Member # 173) on 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
Posted by Pat Moore (Member # 380) on 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...
Posted by Ian Price (Member # 14) on 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
Posted by David Johnson (Member # 173) on 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
Posted by Pat Moore (Member # 380) on 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.
Posted by Christopher Seo (Member # 7) on 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?
Posted by Scott Norwood (Member # 30) on 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.
Posted by Pat Moore (Member # 380) on 07-12-2000, 08:16 PM:
Chris;
What I've encountered from standby current operation is that there doesn't seem to be any benefit from it. We also had more lamps removed due to excessive arc waver (sometimes referred to as "flicker") when they were run on standby. My feeling is that the lamp really "likes" to run within its current range and not change around too much.
As for dowsers, that's a lampmakers decision. On current Strong systems, the cast dowser blade seems to hold up well no matter what we do to it, unless a bulb is horribly misfocused or the exhaust system isn't what it should be. We do that even with 5-7kw systems in theatrical and special venue applications -- with good exhaust -- without problems.
I have seen situations where the manual dowser simply isn't heavy enough to stand the energy on it. Also have seen lamphouses where the reflected light back off the dowser was focused just about right on the anode end of the lamp -- it didn't like that very much...
Posted by John Walsh (Member # 168) on 07-13-2000, 10:11 AM:
Osram suggests running a new bulb at 85% of it's maximum current, then increasing the current as the bulb ages.We found that cooling is *the* most important factor for bulb life. We did not find any real savings by rotating, leaving the lamp on, or running at a reduced current.
If someone is getting poor life out of a bulb, I would check the airflow, but it might actually be poor lamphouse design.
The eariler Xetron lamphouses (XH series (blue colored) did have a 5 minute warning on them. Xetron had several cooling problems with those lamphouses (those made from around 1978 to 1983 or so.) They came with one squirrel blower for the rear, then added a second blowing on the front, then added a 8" stack fan on the top of the lamphouse- all the while requiring a regular roof-top fan. It got to be a joke. I got so tired of their lame attempts (again, this was back in the early 1980's) I tried to fix it myself. I sat there with a cigarette, blowing smoke in to see what happens. While there was lots of air movement, there was some kind of turbulence around the inside front of the reflector where air didn't flow out.
Their newer consoles are pretty good; one blower for the rear and a stack fan. An usher left a 3000 watt console on for 3 hours (dowser closed) with no noticable heat or damage to the dowser. We get so many hours out of a bulb 3K now, (5000+) I change them just because I'm worried they may blow up from darkening.
So, anyway, make the manufacturer support the product and tell them your problems. You may have to do a little work (take cfm measurement, etc.) but with several of the same lamphouses, it probably would be worth it.
Posted by Gordon McLeod (Member # 33) on 07-13-2000, 10:36 AM:
The Ushio lamps are designed with standbye operation in mind. Osrams /ORC are not
also xebex uses electro magnetic stabalisation that changes with arc current.
Also Ushio lamps are designed for a lower ignition voltage compared to OSRAM and ORC