Film-Tech Forum ARCHIVE: Flicker in Cinemecannica Zenith x4000

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Posted by Jeremy Fuentes (Member # 2135) on 03-10-2004, 09:20 AM:

I have a problem with a flicker in this lamphouse. Do you think it is the bulb or the lamphouse. Have not tried anything yet, and do not know the type of bulb that was put in there. The picture is also dark, so I am guessing its an old bulb. Any suggestions?

Posted by Gordon McLeod (Member # 33) on 03-10-2004, 09:34 AM:

How many hours on the lamp and what type of rectifier, has the lamp been rotated?
Those lamphouses produce a good light and usually long bulb life

Posted by Jeremy Fuentes (Member # 2135) on 03-10-2004, 11:32 AM:

Gordon, not sure, I'm not at the theater right now. But I am not even sure that the hours were even logged anywhere when the bulb was first installed. I wasnt working there at the time.

Posted by Larry Zuverink (Member # 1483) on 03-10-2004, 01:49 PM:

I've had this same problem three times in the last 2 1/2 years. Once was the lamp. On the other two it was a diode going partially out. I had a heck of time the first time from never seeing it. The only way to find it was to check each diode with the rectifier on and with a scope to see which one was leaking AC. Definite qualified techs only job!

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-10-2004, 01:51 PM:

If you don't know how many hours are on the lamp, how does the envelope look? Has it blackened much, or a lot, or not at all?

How to the anode and cathode look? Are they pitted to hell?

Posted by John Pytlak (Member # 331) on 03-10-2004, 02:14 PM:

Again, a quick and safe way to check for excessive ripple is to let some of the light "leaking" from the lamphouse shine on a silicon photocell with a resistive load, and look at the voltage output on a scope. Ideal is a "steady state" (DC) output.

With experience, you can estimate the hours on a particular lamp by the blackening of the envelope, and the amount and type of pitting on the tips of the anode and cathode. (Use proper safety gear! [Eek!]

)

http://www.film-tech.com/tips/XENONFAILURE.pdf

Posted by Gilbert Travin (Member # 2138) on 03-11-2004, 03:21 AM:

I think as Larry and John : a partialy "out of order" diode make current ripple and flickering !

Posted by Jeremy Fuentes (Member # 2135) on 03-11-2004, 06:06 AM:

Thanks, guys. I havent had a chance to check the lamphouse again, since I have been off, and will be the entire weekend, but our tech is going to the theater tomorrow, and the problem should be taken care of by someone more experienced than myself.
Thanks again.

Posted by Glen Rich (Member # 1150) on 03-14-2004, 02:43 AM:

It could be any of the above, check the rectifier diodes and the windings.If one of the windings of your rectifier is on the way out your tech. should find minor AC leakage coming from the rectifier to the lamphouse.

Posted by Jean-Michel Grin (Member # 1360) on 03-15-2004, 08:59 PM:

Hi !

Past six month a projectionist told me that he got a lot of flicker on the screen. I checked the rectifier: It was out of order: One selenium diode was burn out. I exchanged the all rectifier for a Irem recctifier, and all we be fine.
Just check all diodes on Your Rectifier. Maybe one coud be shord-circuited, or burned out.

Good Luck !