Film-Tech Forum ARCHIVE: Lamplife Extension Strategy

This is topic Lamplife Extension Strategy in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Martin McCaffery (Member # 37) on 10-08-2017, 06:43 PM:

I have a Solaria One using CDXL-21S1 lamps.

I know the real answer is Get a better projector. Someday.
In the mean time, I'm trying to figure out how to get the best light for the longest time out of the lamps.

As I've mentioned elsewhere, when I install a new bulb and adjust it to 14fl, it is pretty much at the maximum reccommended 81A. Unfortuneately, after less than a month it is down to 12fl and still at 81A. By the time the lamp hits half-life (500hrs) it is down to about 10.5fl.

With about 200 hours to go now, it is bouncing back and forth from around 8.8-9.2 fl, and 77A.

I'll have to get a new lamp soon. So I'm wondering if it is best to turn off LiteLOC and set the lamp to 14fl with 81A and then reduce the ampreage until I am at about 10fl. Would this be a reasonable compromise that would be able to keep the lamp at about this level for the life of the lamp (assuming I make adjustments along the way)? Am I in a situation where I just have to experiment with each new lamp?

So far, I'm the only person who has complained about the brightness levels, but it is driving me nuts.

Posted by Carsten Kurz (Member # 5396) on 10-08-2017, 07:59 PM:

The lower you drive it initially, the longer it will keep. So I guess you need to compromise a bit on these initial 14fL. At these operating parameters, LiteLOC seems to be useless.

Screen choices?

- Carsten

Posted by John Thomas (Member # 6509) on 10-08-2017, 08:59 PM:

When you next replace the lamp, do the following:

Set your power to around 75%-80%, and then enable LiteLOC and set your target there. This way, LiteLOC will have that remaining 20%-25% throughout the life of the bulb to maintain the light level.

At end-of-life, if the current hasn't reached the maximum recommended, you can raise that initial power setting on the next lamp by 5% and see how that works.

In principle, like Carsten said, starting at a lower power will give you more life. Starting at full power guarantees you'll have a nasty flicker before the expected life is up.

Other tips:

Healthy exhaust airflow will keep the quartz envelope clear.

Always run LampLOC when you replace bulbs so the new one is well-focused. If you are using the wizard this is happening anyway.

Avoid hot-striking. Unless it's an emergency, always let the bulb cool completely before striking it back up. I. E. if the feature ends and the next show's preshow starts 10 minutes later, just leave the bulb on.

Posted by Gordon McLeod (Member # 33) on 10-09-2017, 08:31 AM:

Actually there is no issue on hot striking the lamp

Posted by John Thomas (Member # 6509) on 10-09-2017, 02:01 PM:

Gordon that's an interesting assertion. I have always been told hot-striking was a no-no by people with many more years in the booth than me.

I'm always thrilled to dispel technical superstition so if you have some data to back that up I'd love to see it. Granted I have no data either way so I'm just curious to know where you're coming from.

Posted by Sam D. Chavez (Member # 1841) on 10-09-2017, 05:23 PM:

Osram had a rule of thumb that each bulb strike was an hours worth of lamp life. Don't know if there was any science to it

Posted by Jack Ondracek (Member # 1466) on 10-09-2017, 05:39 PM:

quote: Sam D. Chavez
Don't know if there was any science to it

Well, if not, it sure seems a lot of people have adopted it. Having heard that from people I consider credible, I believed it, too.

In any case, since most of us are at one strike per show, if not the whole day, I doubt it affects us much. I keep track of the number, more for interest than anything else. Since going digital, alignment, warranty hours and power management are about the only factors that seem to matter a whole lot.

Posted by Gordon McLeod (Member # 33) on 10-09-2017, 07:13 PM:

The rule of thumb was 1 hr perstrike
Ushio engineers actually told me the best way to prevent premature flickering on the 1.8ksd lamp was to hot strike it occasionally
Xenon lamps were always considered a hot strike lamp

Posted by Sam D. Chavez (Member # 1841) on 10-09-2017, 08:12 PM:

Define engineer. Both these companies have "sales engineers. It's rare to see an actual expert at a trade show."

Posted by Leo Enticknap (Member # 534) on 10-10-2017, 01:54 AM:

I was told half an hour of lamp life per strike, but that was in the 1990s and in relation to film projection. I guess that with the shorter arc in a digital-optimized lamp, each strike whacks it a bit harder, so to speak.

Posted by Gordon McLeod (Member # 33) on 10-10-2017, 11:14 AM:

I have his card somewhere but he was from Japan and spoke through an Interpretor it was at the IES trade show

Posted by Mark Gulbrandsen (Member # 72) on 10-11-2017, 04:12 PM:

Martin,

What gain. size and condition is your screen? A new screen can make a world of difference in some cases. Am at a site today that we decided to replace one of the four upstairs screens in the next quarter because the situation is similar to yours. Across the hall is Screen 2 that is 1/3 larger but only a 4 year old MDI 1.4 gain screen. The difference in brightness between the two rooms is astounding.

For lite-Loc to work you would have to start out considerably lower in amperage, so there would be sufficient head room left for Lite-Loc to slowly bring the current up to maximum rated amperage. Another way to monitor this would be to start out at say 12 FL and manually monitor it every 100 or so hours of operations and make a graph as to lamp age rate.

Mark

Posted by Martin McCaffery (Member # 37) on 10-12-2017, 03:39 PM:

The screen is probably overdue, but will have to be put off. Probably when we upgrade projector in a few years.

I'll try starting lower with Lite-Loc and see what happens.

Posted by Mark Gulbrandsen (Member # 72) on 10-13-2017, 10:17 AM:

Well, unless your screen is really large, then changing the screen is way cheaper than changing the projector. And it can actually make up some of the difference in light level... some times. I would recommend getting 1.4-1.5 gain screen samples from Harkness and MDI and compare to what you have now. That shouldn't cost much to do if anything.

Mark