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Author Topic: Picture flicker on Christies Frank Dubrois Jedi Master Film Handler Posts: 896 From: Cleveland, OH Registered: Mar 2005 posted 03-28-2007 11:07 PM                    Our picture flickers. It almost looks like the shutter is slightly out of time, however, it is not. I not only replaced the entire assemblie, but retimed it as well. A brand new bulb was put in, however, nothing has changed. There was a somewhat large amount of dirt (belt dust, leaking bearings = mess) on the inside of the projector, but nothing really seemed out of place. The shutter belt was worn down a bit and replaced. So why is this still flickering? Could it possibly be a diode? Usually if its a diode, the flicker is much more pronounced, this is bad, but not horrible. Bright white scenes are intolerable for ME to watch, however, we have not received any complaints.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-29-2007 12:42 AM                     Bulb is focued in too close to the trap and gate. Back the bulb off a bit. quote: Frank Dubrois Bright white scenes are intolerable for ME to watch ..this was the first clue that tipped this off.  |  IP: Logged Dustin Mitchell Phenomenal Film Handler Posts: 1865 From: Mondovi, WI, USA Registered: Mar 2000 posted 03-29-2007 01:13 AM                     Actually it sounds like a diode problem.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 03-29-2007 02:21 AM                     If it is a diode, the picture will be fairly dim and the flicker to a ridiculous level. I'm with Monte on this one, the bulb is probably not focused properly. Are the bright scenes REALLY BRIGHT? If so, that's your problem. The bulb needs to be focused properly. Of course those Christie lamphouses DO put off one hell of a lot of light, so maybe you will want to swap that out with a Strong or something.  |  IP: Logged Alex Grueneberg Expert Film Handler Posts: 125 From: Chicago, IL Registered: Aug 2004 posted 03-29-2007 03:47 AM                        I've noticed a few houses like that here and the bulbs are focused properly (trust me). How common is it for the diodes on these to fail, and do they ware down over time? Or is it simply, it lights or it doesn't. As an example lets say i have a 7 year old SLC with more then likely original diodes with 2k in a 100 seat house. The shutter is correctly timed as well. Any light (white) looks like a slight subtle strobe effect in the light output and really bothers me but since customers don't complain no one else cares.  |  IP: Logged Frank Dubrois Jedi Master Film Handler Posts: 896 From: Cleveland, OH Registered: Mar 2005 posted 03-29-2007 06:43 AM                    Alex, that sounds like the issue I have. I've had a SLC lamphouse that had a bad diode where the lamp lit, but the flicker was ridiculously obvious. It was almost like a blinking rather than a stobe. I will check on the bulb issue and see if that solves it, if not, then back to the drawing board.  |  IP: Logged Ian Woloschin Film Handler Posts: 54 From: Worcester, MA, USA Registered: Mar 2006 posted 03-29-2007 06:44 AM                        I've noticed similar problems with my two DP-70s with Christie lamphouses (with 3K bulbs). I kept noticing a strange flicker, but no one ever complained, and other people in the booth seemed to not notice it until I pointed it out. I had a technician come in to fix some other problems we were having and asked him to look at the flicker. Unfortunately, someone else was covering for me in the booth when they checked out the flicker problem, and neither of them were able to really see the flicker or notice any problems.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-29-2007 09:05 AM                        Electrical problems aside, there are 2 other possibilities: 1. Slight mis alignment will yield a "shimmer" when light is very bright 22 ft/lm or more. 2. I assume you have the Christie (no gears/but fears) projector. One of the design errors of that macine is that the shutter is small and close to the film. When very bright the "sharp, optically" edge will be in focus and will be more visible. Louis  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-29-2007 09:32 AM                     quote: Louis Bornwasser One of the design errors of that macine is that the shutter is small and close to the film. When very bright the "sharp, optically" edge will be in focus and will be more visible. Actually you need to check and see if you have double or single blade shutters on your P35GP's. The single blade P-35 does not suffer from the flicker that plagued all double blade P-35's. Any double blade P35GP is convertable to single blade and the conversion takes about 20 min. per machine. Aside fomr elimination of all flicker there is also an increase of about 5% of light output. Re the DP-70 guy: Check your filter caps in your rectifiers... the ripple may be too high. Not many techs can properly check this. Also, running with a high leg on three phase AC can cause flicker on some rectifiers. Also, make sure your on screen light level is not too high... this is easy to do with a DP-70 although the double speed shutter cuts off very fast allowing higher than nor al light levels. We have run them as high as 22fl with out any visible flicker.. Mark  |  IP: Logged Demetris Thoupis Phenomenal Film Handler Posts: 1240 From: Aradippou, Larnaca, Cyprus Registered: Apr 2001 posted 03-29-2007 01:58 PM                     We had an issue with a rectifier and it proved that it had a couple of bad diodes. What I always do is change the whole lot with new ones which are exactly the same. Even though they might have the same specs, an old bunch has some deterioration. What did happen to this house was that when the projector was not running, the lamp performed perfectly. When the projector did run, the lamp had something like a dimming up and down a very low one but really disturbing. It took me a while to figure out that it was NOT the projectors' problem but actually the rectifier. Changed the whole lot of diodes and the problem solved. Demetris Sorry for the edit. What you should check, is check the lamp without any film running. That will tell you what is going on.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-29-2007 03:14 PM                        This problem is more pronounced in 60Hz countries. (12 Hz beat vs 2 Hz beat.) Louis  |  IP: Logged Frank Dubrois Jedi Master Film Handler Posts: 896 From: Cleveland, OH Registered: Mar 2005 posted 03-29-2007 05:11 PM                    Wasnt lamp focus....I suspect diodes. This isnt the type of problem you can test the diodes for is it? If I'm not mistaken, the diode tests ok until a load is put on it, then I get this flicker Why do some diodes read differently then others? Is a higher number better or worse?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-29-2007 06:25 PM                     Remember to ALWAYS replace all the diodes at the same time. I reccomend the Semikron 160 amp diodes in the same size package as the 85 amp jobs that are in there. All you need do is drill the loke a bit larger for the metric thread. Irem uses the Semikrons in all their products. Mark  |  IP: Logged Alex Grueneberg Expert Film Handler Posts: 125 From: Chicago, IL Registered: Aug 2004 posted 03-29-2007 07:23 PM                        Thanks for the input ya'll! I found a brand new diode rack with the plates, slightly higher gage wires with better connection points with slightly larger diodes barried in our supply area. After speaking with my tech I got the ok to swap it out. #7 now looks beautiful! A shame Dead Silence is playing in it but at least its scope. Now all I need to do is get these couple of spit balls off the screen that I noticed while doing all of this.. Typical.  |  IP: Logged Demetris Thoupis Phenomenal Film Handler Posts: 1240 From: Aradippou, Larnaca, Cyprus Registered: Apr 2001 posted 03-30-2007 02:31 AM                     Important tip! The best way to check whether its your projector timing is just throw straight light with no film. If the flicker is visible go straight on the lamphouse/rectifier. If not then there you go on the projector shutter timing. Demetris  |  IP: Logged

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