This is topic Focusing Lamphouses in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Randy Stankey (Member # 64) on 09-22-1999, 11:40 AM:
Just a quick question.Do most lamphouses use the same general procedures to focus/align the lamp?
I'm used to doing the alignment on a CFS lamphouse but I've never had to do one on a XELAMP.
We just put in a new screen and it has a lower gain than the last one. (The last one was a Da-Lite beaded screen, this one is a Hurley SuperGlo.) I noticed that the lower brightness makes the focusing of the lamp more critical, so I plan to tweek it.
I guess you just take the lens out and run the projector and adjust the alignment just like any other. Right??
Posted by Joe Redifer (Member # 3) on 09-22-1999, 07:28 PM:
You could do that, but that is not the way I like to focus lamps. Here is what I do:Switch the lens and aperture (and masking) to scope. That is your biggest format, unless you happen to be running 1.33 (biggest aperture opening). I focus the bulb forward until I see a definite hot spot on the screen, then I use the left/right and up/down controls to make the hot spot centered. Then I back the bulb up so none of the corners have any shadows. Removing the lens can assist with this so that there is less adjustement to do, but just the process of that takes longer. Also, when focusing the bulb, remember to close the hand douser for a few seconds to let the lens cool every once in awhile, or you can damage the lens if you leave the lamp on it overfocused like that for an extended length of time.
Keep in mind that you will have to focus the bulb forward a little bit when running flat, or the picture will be substantially dimmer. I always thread a loop and run it just to make sure the film doesn't burn. If the loop can handle it going through the projector again and again and not burn, then the print can definitely handle it going through once really quickly. I get excellent results, at least 16 footlamberts. Sean James from Christie told me that I was probably getting more than that (on a 4K lamp, no film damage).
Posted by Randy Stankey (Member # 64) on 09-22-1999, 11:08 PM:
Thanks, Joe. -- Big Help!I used to focus it that way until our tech at TT17 told me to do it the other way. He said that it was more accurate that way. I think I prefer YOUR way. We DO have Acad. but we use it MAYBE once a year. I'll do the focusing on that one when the time comes.
I'm shooting a 2K watt bulb onto an approx. 13 X 31 screen from 104 feet away. (110 feet on the Hypotenuse) Simplex-XL / 5-Star -- Strong PS. / XELAMP LH. -- Burning at approx. 94% rated wattage. (25v - 75a = 1875w) And the North Star is approx. 42 deg. above the horizon at Midnight. 
Posted by RICK HAMILTON (Member # 115) on 09-22-1999, 11:26 PM:
I think that I've intentionally tried to damage a lens, but even after leaving the lamp on for 36 hours straight, the CFS just can't do it!
Posted by Randy Stankey (Member # 64) on 09-22-1999, 11:31 PM:
You're probably right but I never tried. The little Xelamp WILL toast a lens pretty quickly, I think. I did the old "Let's fry some old film" test on that one once. -- Less than a second. It took a 4500W CFS at least two or three to get a good size hole.
Posted by Joe Redifer (Member # 3) on 09-23-1999, 01:56 AM:
I may be a little over-paranoid about damaging the lens with direct light and no film, but that has never happened to me. So therefore I do not know how long it takes to damage a lens with either aperture on a 4,000k or even a 2,000k. Anybody have any real world results? I don't think I want to leave my lamps on 36 hours to find out (they warp a closed changeover within about 10 minutes).
Posted by Brad Miller (Member # 2) on 09-23-1999, 02:56 AM:
Just thought I'd chime in with full backing to the technique Joe detailed above. However, I do find that removing the flat lens and doing the ol' target assists in lining up everything to start with, but is only really necessary if there is doubt of a reflector or other item being out of alignment. I always check the target when I first go into a theater. Once I'm sure everything is aligned satisfactorily, I use Joe's method.
Posted by Rick Long (Member # 213) on 09-23-1999, 08:50 PM:
I think it depends a lot on the lens. At one theatre, inexperienced projectionists (ushers) managed to burn two Wollensak lenses on us by leaving the lamphouse on all night with the projector running and the dowser and change-over open. Our last substitution (the only one available) was a Schnieder. Same staff, so far, no burn.
Posted by Joe Redifer (Member # 3) on 09-24-1999, 05:29 AM:
Actually this reminds me of when I was working for the lovely United Artists Theatre Circuit, and a theatre that we had just reopened (the Continental) was doing incredible business, thanks to their 800 seat house and a nearly 80 foot screen with an insane curve. Well, to get to the point, somebody left the lamphouse on one night (in the big house, of course) and basically what happened is that they burned a hole in their shutter. This was a Christie single blade, which was new at the time. All of the other 5 houses use double bladed shutters, so they couldn't rob one from the smallest house. Whoops! I wish I was there when it happened, but I wasn't working at that particular UA anymore at the time (I always helped during install and worked the booth for at least the first week, then split back to my main theatre).
Posted by Aaron Sisemore (Member # 145) on 09-24-1999, 09:08 PM:
Back in 1985 I had shut down for the night at the Phoenix (see the pic warehouse), went home, and got a call from the manager at about 4 am that the janitors 'smelled something burning' from the projection booth. Well I got in the car and went to the theatree and opened the door to the booth and the booth was filled with acrid smoke, and the temp in the booth was pretty high! then I saw WHY the smoke and heat: the lamphouse was STILL ON and the bulb still lit running with zero cooling! I immediately turned the main shutoff for the 3-phase off to kill the lamphouse and turned the exhaust fans to clear the booth of smoke. After things cooled a bit, I grabbed the lamphouse keys and opened the lamp. Almost all of the plastic parts in the lamphouse had melted down, wires had insulation melted off, the reflector was discolored badlt, the rubber insulators that kept the anode spider from shorting against the reflector were redused to ashes but provided enough insulation to prevent shorting, the bulb was totally black, but INTACT ( I to this day am amazed it didnt explode)..to put it lightly it was a real mess. Called the manager who called an emergency tech who arrived at 7 am with a junker lamphouse ( Xetron XH2000) and rebuilt the lamphouse in time to get back onscreen...The cause of this mess? A little interlock switch that detected the airflow from the lamphouse fan had stuck closed keeping the rectifier contactor closed ( in the original wiring for the booth here the 3 phase and contactor were on a separate circuit from the rest of the lamphouse circuits) The tech fixed that problem and the contactor won't close unless the lamp 'on' switch is closed...
Aaron
Posted by Randy Stankey (Member # 64) on 09-29-1999, 05:38 PM:
I've been working on the focus of my lamp today. I've been unable to get a satisfying result.It seems like something is out of alignment. I took out the lens. (After about 10 min. of trying with the lens in.) The usual 'bullseye' wasn't centered on the screen and it wasn't very much of a 'bullseye', either. (More like a 1/2 circle.) I just set it for the best light I could get and left it at that.
I'm beginning to think we're a little but 'under-gunned' here. I think the old, beaded screen was just not showing the effects of a misaligned lamp as much as the pearlescent one, since it was more reflective.
After the show, I'll try again and let y'all know how it came out.