Film-Tech Forum ARCHIVE: 4K lamps

This is topic 4K lamps - Osram Vs Ushio in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Chris Byrne (Member # 1563) on 03-06-2004, 06:36 PM:

I don't want to enter yet another debate about which bulb is best, but I do have a specific enquiry regarding both OSRAM and USHIO bulbs.

I am running only one cinema that uses 4K lamps and when told a change to Osram was for the better I dived at the chance.

From day one a brand new 3600HN lamp (ushio) would develop a slight flicker (not overtly noticeable on screen until around the 2000 hour mark.)

On the other hand the 3600w/htc lamp (osram) starts out with brilliant light, yet the last and only two I have used have started to develop a noticeable flicker around the 1200 hour mark.

Equipment used is a USHIOKCX140U4 rectifier and Xebex Supersol(N) lamphouse.

The two Osram bulbs that I have used have both arrived with anode lead attached, however I am told this is not a standard purchase. Is there any difference to the bulb that comes separate of the anode lead?

I am thinking seriously about swapping back to Ushio, should results not improve with the 3rd Osram I have on order. One thing that I can't deny is that others have had better results with the Osram style xenon.

Posted by Steve Kraus (Member # 476) on 03-06-2004, 06:45 PM:

Have you measured the ripple on this unit? Is cooling adequate?

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-06-2004, 07:22 PM:

You said you were using 4kW lamps. Both lamps you listed are 3.6kW lamps.

Are you sure you are running the lamps within (or around) their operating range of 120 amps (min 80, max 130)?

I believe the warranty life on the Osram is either 800 or 1000 hours. The Osram lamp is supposed to come with the lead attached.

I've had good luck with the XBO 4000W/HS. If you can handle the larger anode and cathode base sizes, you may want to try one out.

Posted by Gordon McLeod (Member # 33) on 03-06-2004, 07:38 PM:

Some of the SUpersol Lamphouses had a adjustment for the current in the electromagnet for stabalization
Also are you using the standby mode on the sanrex rectifier?If it is the SCR styled and the standby is set below 1/2 the rated current the ripple is very high and flicker will result

Posted by Chris Byrne (Member # 1563) on 03-08-2004, 01:15 AM:

Hi Guys,

Thanks for your help.

Firstly I haven't checked the ripple and don't know how. Can anyone supply a link or give instruction how to do this?

Secondly the cooling is fine. It is regularly cleaned and checked for airflow.

An engineer tong tested the current flow and found a 4A differential between rectfier and lamphouse meters. I never run the lamps above 125A (within specified range.)

We don't have Standby mode operational on our lamphouses, but what is the SANREX SCR you are talking about?

Also, while I know the bulbs are 3.6KW, I have been informed that they are now all referred to as 4K lamps. Is this untrue?

Thanks again [Wink]

Posted by Gordon McLeod (Member # 33) on 03-08-2004, 09:33 AM:

Sanrex made 2 types of rectifiers commonly for use with the Xebex lamphouses (at least the ones over here)
One style the older was a magnetic amplifier style using a saturable core reactor to regulate and adjust the output current
The later ones used a 3 phase SCR bridge to allow current adjustment
The problem is if turned down to far the output becomes very dirty from the chopped wave form
But since you are not using standbye then that isn't an issue
To measure ripple measure the AC component across the meter shunt

Posted by John Pytlak (Member # 331) on 03-08-2004, 09:58 AM:

Another way to measure ripple is to let a bit of the light leaking from the lamphouse shine on a silicon photocell with a resistive load, and look at the ripple on a scope:

http://www.sylvania.com/business/photo/pdfs/ENGR_BLTN11.pdf

Osram XBO Theatre Lamp Technical Manual
See pages 17-18.