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Hi all;
In "Lamps, Lamps..." the subject of arc waver/flicker came up. I am wondering how related it might be to lamp rotation, if it's related at all. Some manufacturers require rotation as part of their warranty coverage, others don't. I've heard recommendations against it, and heard operators claim they get best performance rotating 90-degrees at each fourth of the warranted life. So...
1) Do you rotate as a practice?
2) Do your lamps and/or company policy require rotation?
3) What is your rotation schedule (180-degrees at half-life, etc.)?
4) Has rotation ever caused any problems?

Thanks,

Pat

I have always followed the OSRAM suggestions.
Rotate lamp 180' at half warrantee life. I
have modified it slightly..that I now rotate bulbs every 1000 hours or so. (Whenever our
service call hits) I have noticed that the low pressure baulbs (Japanese, Chinese, etc)
suffer from unstable arc untill they reach
200-300 hours after a rotation. Also they can
be 'hard strikers' The high pressure lamps
such as OSRAM do not have the arc fluctuation
but they almost always are 'hard strikers' for about 100-200 hours after rotation.
I have never had any reported failures of lamps with the fill tube at the 12 o'clock
position. I have experienced a greater than
normal amount of filter capacitors in the power supply weakening..its probably due to
the average age of the majority of them I
service!!! Hard lamp starting can most times be directly related to weak capacitors in the
power supply, by not being able to store enough current to hold the arc when the igniter sparks it over...Of course, like gasoline, caps are not getting any cheaper!!!

I strongly (no pun intended) discourage the placement of the evacuation nipple on top.
Particularly with some of the poorer quality lamps such as the ones from the far east (includeing ORC)
In some of the older Osram warranty notes they did state they would disallow a warranty claim on a lamp that showed via blackening that the nipple was on top. I don't know if that still is there policy.
I rotate 180 degrees at half life and then increase the lamp current at the same time to help it to stabalize

We do rotate.... carefully!...... and I'm printing this out to post in the projection room. Good stuff.

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Mike Hurley
www.bigscreenbiz.com

There have been several recent threads over on the Film-Tech Film Handlers Forum regarding lamp rotation:
http://www.film-tech.com

Proper rotation evens out the blackening of the lamp and wear on the electrodes. Some say it also helps compensate for the "sagging" of the red hot electrodes over time. Follow the lamp manufacturer's recommendation. But always check lamp alignment and focus after rotating to be sure the image has the correct 16 footlambert screen luminance and good uniformity.

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John P. Pytlak, Senior Technical Specialist
EI Worldwide Technical Services
Research Labs, Building 69
Eastman Kodak Company
Rochester, NY 14650-1922
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