Film-Tech Forum ARCHIVE: Unsteady light output (fluctuations) Osram 1kW - V5 - CX16H

This is topic Unsteady light output (fluctuations) Osram 1kW - V5 - CX16H - IREM X50DM in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Sverrir D. Thorarinsson (Member # 3372) on 07-13-2007, 04:58 PM:

Hello,
I'm experiencing unsteady light output in one of two auditoriums. On screen it looks like the light is floating on the screen. The light output is also low. The bulb glass is quite smoked but the lamp has still 500hours left. It's running at 55Amp (according to the ammeter on the lamphouse). Ventilation looks alright, I measured no more than 35-40°C in the lamphouse itself. (outside temperature is 19°C)

I have two things that might help:
1. The heat in the projection booth is very high, my readings show 31°C. The heat in the lamphouse is low but all other things on the projector and other equipments are very hot. Figures:
The projector wall (treading path) is 54°C
Film gate is 60°C
Lenses are 55°C
Lamphouse walls are between 41-56°C
Rectifier walls are between 45-52°C

2. A 1600W lamp was once running on the rectifier but he is only designed to produce 30-50A (according to the info on it), resluting failure, I don't know what failed in it but isn't it possible that something else has gone bad because of the too large lamp?

The bulb has never been rotated and there is no arc stabilization. (the projector is tilted very little)

I would also like to note that this is not a cinema I work for, I'm only working here for 3days because of staff issues, but I would like to solve this issue because I know,no one else will.

Equipments:
Cinemeccanica Victoria5 with CX16H lamphouse
IREM 3phase rectifier type N3-X50DM
Lamp: Osram XBO 1000W/HSC OFR (rated lamp A: 50Amp, range: 30-55Amp, lamp life: 2000hours)

Isn't the fluctation caused by unstable arc burning? I think it's not caused by the rectifier because that would describe it self as regular flicker or something like that.

All help is very much appreciated.

Best regards,
Sverrir D. Thorarinsson
Iceland

Update:
I measured the exhaust from the projector and it's 55°C, I guess it's acceptable, but the anode/cathode glow quite bright after shut down. -More than in the cinemas I work usually for.

[ 07-13-2007, 07:00 PM: Message edited by: Sverrir D. Thorarinsson ]

Posted by Demetris Thoupis (Member # 833) on 07-14-2007, 12:18 AM:

I once had something similar although I am not sure if it is the same case. The light on the screen was doing something very strange when the projector was running with no film. The light would dim up and down looking like the projector speed was not steady in a standard pace. Although this looked like a projector issue, the rectifier had some faulty diodes (not burned) and when I replaced all of them the issue was gone. Are you certain that inlet and outlet exhausting in your lamphouse is addequate? Smoked bulbs are not a good sign. Perhaps you have not so tight connection on the bulb or the "hose" is not directly aimed at the edge of the lamp.
Demetris

Posted by Monte L Fullmer (Member # 2797) on 07-14-2007, 02:34 AM:

being a darkened envelope with 500 hrs to go, I'd call it a bulb that has reached the end of it's life - even though that 1k HSC has a 2k warranty and the amperage run is in the normal range for that size of bulb.

Could also that the existing, and/or previous exhaust isn't sufficent to pull the air around the end seals.(esp, with those HOT temperatures that the machine is experience that you've documented..). It may seen sufficent, but I can safely bet that the bulb is actually being overcooked with insufficent exhaust...AND, the bulb wasn't allow to cool down (with exhaust fan still on) when bulb was turned off.

Time for a change .. I would say that the bulb was just one of those that got defective before warranty. I've seen a few OSRAMS fail before warranty like this.

good luck - Monte

Posted by Mark Gulbrandsen (Member # 72) on 07-14-2007, 06:56 AM:

Adding arc stabilization would be a good idea although I don't believe it is an absolute requirement for this lamp. Also sounds like you need better cooling. The darkened envelope is a clue that things are running too hot. Today's lamps have a "getter" in them to attract the spent tungsten so it does not end up darkening the inside of the lamp envelope. That exhaust air temp., 55 deg c. is pretty high for that tiny lamp. You should have about a 750cfm exhaust blower on that lamphouse with that size lamp. Also be sure that the lamp connections are tight... loose connections can also cook a lamp and will discolor the metal ends. In Iceland cooling shouldn't really be a problem.... and you're at about sea level right....

Mark

Posted by Gordon McLeod (Member # 33) on 07-14-2007, 10:20 AM:

I would check the internal air ducting in the lamphouse to ensure that the air is directed where it is required many cinemecanica lamphouse use tubing to blast air at specific points of the lamp and reflector
I would find out what the air intake fan is rated at
You will probably cause more damage to other parts of the lamphouse if one attempts to draw out much more air than is being blown in as most compact lamphouses were designed for a very specific air current inside them

Posted by Mark Gulbrandsen (Member # 72) on 07-14-2007, 12:37 PM:

quote: Gordon McLeod
You will probably cause more damage to other parts of the lamphouse if one attempts to draw out much more air than is being blown in as most compact lamphouses were designed for a very specific air current inside them

I defiantely disagree with that statememt! You cannot overcool a lamp and the mirror will be much happier and longer lived in a cooler environment. Extra cooling WON"T cause it to crack, the mirrors are already stress releived when manufactured. Add some extra cooling to an ORC 1000 and the things never die [thumbsup]

.

Mark

Posted by Richard Fowler (Member # 893) on 07-14-2007, 02:47 PM:

The CX16H uses a "muffin" type of fan which if dirty or needs replacement will not pressurize the the rear chamber of the lamphouse to adequately cool the 1600W/HS bulb. If the reflector cold coating is bad, this unit runs hot.

Posted by Sverrir D. Thorarinsson (Member # 3372) on 07-16-2007, 09:20 AM:

Thank you guy's so much for good answers, I'll have a look at the diodes, I'll also ask the guy's at that cinema about whatever or not they allow the projectors to cool down properly before shut down.

Hehe, funny that you should note that heat shouldn't be a problem here in Iceland, Mark Gulbrandsen, because we are breaking heat records here almost daily now! (for Iceland) Buildings here are designed to isolate heat inside over the winters but because of "global warming" we are starting to have problems because of the higher heat here.

I'm in contact with Sound Associates in UK to get advice for the ventilation.

Regards,
Sverrir D. Thorarinsson
Iceland (not so icy) [Big Grin]

Posted by Sverrir D. Thorarinsson (Member # 3372) on 07-17-2007, 02:16 PM:

I have ruled out the rectifier, I've checked all caps and diodes and monitored the outputs with scope. The reflector in the projector is ok.

My guess is that the lamp is not allowed to cool down before shut down and cooling is also not enought.