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Author Topic: Ballantyne flicker Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 05-21-2001 11:34 PM                     Well, I now presume it is happening on both machines, and I presume the lamp currents and voltages are correct. I also presume there is no 12hz flicker. Throttle back on the lamp, or go to a smaller xenon bulb. Also, operating the rectifier outside the parameters (especially over maximum rating) is not a cool idea - no matter how much cooling you provide. The filter capacitors will not adequately filter the AC component out of the DC.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-22-2001 10:08 AM                     In many screening room where they have too much light we insert a piece of stainless steel screen material between the lamphouse and the trap. In fact we mounted them in a empty heatfilter holder  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 05-22-2001 05:10 PM                     I notice that you said at time the current goes down and the voltage goes up. This indicates a change in the load on the power supply. Check to see if you have any loose or dirty connections. I agree that the filter caps. are not sized to handle the increased current for the 2K lamp.  |  IP: Logged Scott Balko Expert Film Handler Posts: 136 From: Redwood Falls, Minnesota, USA Registered: Apr 2000 posted 05-23-2001 05:10 PM                     Yep, it happens exactly the same with both projectors. However, my other power supply has a very constant reading on the amp and voltage meters. That tells me that I've got problems in my power supply, correct? Anyhow, you guys have been a wealth of information. I thank each one of you for your input. I'm having some 3 blade shutters made, so hopefully that will take care of the flicker. Anybody want to trade some 1600 watt bulbs for a pair of 2000's. The bulb is very clear except for one little spot by the fill knob. Anybody have a pair of 1500-1600 watt bulbs for sale?  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 12-06-2002 03:22 PM                     Now I have also noted a problem similar. I am running a Simplex XL (has a black shutter) and the theatre has a 41-foot throw, very large screen. I have this flicker on another also. But it is not quite as bad. It is more noticable in only one house. The third house (which is actually House No. 1) has about the same size screen, but there is no flicker. The light on all three screen meets (but does not exceed) SMPTE standards. All three setups have Super Lumex lamps, with 3,000 watt Strong Switchers. I am running identical currents (90 amps) on the 2500 watt Christie CH-25 lamps. All three Simplex XL's are identical, equipped with straight gates. Shutter timing is perfect, and flicker I discribe is not a srobe flicker like you would expect to see if a diode failed in a reactance power supply. The flicker does not really appear to be a picture jitter, as the registration of the picture on the screen is steady. With the projector stopped, shutter open, CO open, and lens removed reveals absolutely no flicker. Insertion of the lens, running the projector with no film, the small amount of flicker you would expect to see is very normal. With film running, the flicker appears to be at a 24Hz rate. Lamp focus is normal, with a flat field. I wonder if I have a Switcher problem, or a gate problem. I have not swapped gates around with the machine that does not flicker. Not yet, anyway... Help - any other suggestions? I have this feeling swapping gates around is not going to solve the problem. Is there a possibility it could be a switcher problem that will show up more noticable with film running in the projector?  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 12-06-2002 05:34 PM                        Paul, I haven't experienced much trouble with switchers. However, at the frequencies they run at, I wonder where in the circuitry you'd get a frequency that would cause any noticeable variation through the bulb. Considering the components are all designed for the high freq operation, I'd think something that noticeable would also be heating things up pretty well in the supply... if it was possible at all. Doesn't the transformer in there run off of the high-freq voltage? It probably wouldn't be very efficient if something were to lower the oscillator, and you'd probably see that in lousy current, if it'd work at all. (Hope I didn't put my foot in it... but I don't see how the switcher could be doing anything you wouldn't see on the ammeter). Past that, it'll be interesting to hear what you find. It sounds like you've covered it all. Can screen-type push something like this over the edge? If you're close to overlamping, would a screen with too much gain highlight a problem that might not be noticed in another room?  |  IP: Logged Pat Moore Master Film Handler Posts: 363 Registered: Mar 2000 posted 12-06-2002 06:32 PM                     Some good comments above, but it seems like we need some definitions cleared up and a better description of the problem. I think Gordon is highlighting the most important question -- how much light is actually on screen? Is the complaint actually "flicker" or something else? Flicker is probably best defined as a pulsation of the light level on screen that's noticeable or objectionable. Experience tells us the primary cause is excessive AC Ripple in the DC Current to the lamp, normally caused by an open or shorted diode or other rectification / filter problem in the power supply. Flicker would be evident on the entire screen and is quite different from "arc waver", another light sourced based problem visible on screen. Arc waver is movement of the DC arc or plasma ball in the lamp that actually creates a moving light pattern on screen. A projector's effect on flicker from the shutter (a 48HZ pulse) is visible at high light levels on a white light screen. Depending on the projector's optical characteristics, shutter flicker becomes objectionable somewhere above 18-22 foot-Lamberts. However, the effect could be invisible still depending on the film being shown and its density. That's why SMPTE has minimum and maximum light levels as standards. On the surface, this problem sounds like too much light on screen. The Ballantyne is a very efficient projector light wise and unless there is ghosting, I don't think the problem is in the head, assuming all else is normal. Pat  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 12-06-2002 06:57 PM                     Pat, it looks like a "Flicker Flutter" - (Now that's a mouthful) I wish I could describe it better. I might have a gate problem in conjunction with what I thought might have been a power supply problem. I have never seen this particular problem before in my 35 years in the booth. I am going to swap gates tomorrow, and I will report back as to whether it got better, got worse, or went away. I might add this: Seems lile it is worse at startup of the movie. At the end credits, the problem seems to be gone.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 12-07-2002 04:10 PM                     It is definately a gate problem. I have a picture jitter of 24hz, and a focus flutter to boot. These machines rebuilt under 2 years ago, but the guides and other crtitical gate parts were not replaced. A bunch of new parts and some major readjustments should correct the problem. I did note one of the intermittent movements is also out of adjustment, and backing off on the lamp focus has definately helped reduced the jitter and flutter, but it is still there.  |  IP: Logged

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