Film-Tech Forum ARCHIVE: Lamps for changeovers: Leave 'em on or off?

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

Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 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...

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John Walsh
Film God

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

posted 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.

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Gordon McLeod
Film God

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

posted 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

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