Film-Tech Forum ARCHIVE: Picture flicker on V5 with Zenith X2000H

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Posted by Marin Zorica (Member # 1716) on 03-14-2010, 06:13 PM:

I have one booth with changeovers, both Cinemeccanica Victoria 5 with 1600W xenon @55A screen is 8m wide in scope, when running without motor light is great and no flicker, when running with motor there is flicker in screen, not big, but still noticeable...was thinking on diodes, but than it would be fading in/out and not so fast, and is same on booth projectors, shutters are perfectly in sync as there is no stretching over picture or so. Rectifiers are 3phase with choke on output to reduce AC ripple, and I doubt is anything with them as they did work in one house before and it was okay, even i could check ac ripple.

So was think of shutter on V5 is maybe made with small open or something, as I head from friend he did have some problem with shutter on V5's?

Posted by John Wilson (Member # 269) on 03-14-2010, 06:29 PM:

I'd look at having the shutter gearbox replaced. It's a common issue with V5's.

Posted by Marin Zorica (Member # 1716) on 03-14-2010, 06:48 PM:

Shutter box? Hmmmm...but same problem, with same level of problem on both.....and shutter gear it seams to run fine, without any noise or so? Why you think on that, wear gears inside or?

Posted by Kenneth Wuepper (Member # 1174) on 03-14-2010, 06:52 PM:

Marin,

You stated that the flicker is in BOTH machines. Did it start at the same time? That would not point to mechanical problems.

There is NO flicker when just white light and no shutter in the light path.

The flicker is seen when the machine is running and there is NO film in the gate.

Does the flicker appear when a film is being projected?

Is the flicker noticed only in the brighter parts of the scene? (Like the sky in outdoor scenes)

How many blades are on the shutter, 2 or 3? Running white light with a 2 blade shutter can cause visible flicker also excessive image brightness can cause it.

Depending on the frequency of your 3 phase power source, the pulsing from a diode or phase failure could also be easily seen as flickering. By all means check out the ripple on the DC to the arc.

Hope this is helpful.

KEN

Posted by Marin Zorica (Member # 1716) on 03-14-2010, 07:02 PM:

When projector is not running there is no flicker, just white light on screen, when is running there is flicker, also when is running with film, but then you can see it only on white sceens.
I don't think brightness is too high, as there is 55A on 8m wide screen. This machine were used allready, even don't know did this was before.....now it is, and same on both, even I don't think is soem phase or diode failure as there is same on both, and rectifiers are okay. Shutter is 2 blade type here.

Posted by Ian Parfrey (Member # 5122) on 03-14-2010, 07:07 PM:

All the above...

...and also if the flicker is constant in frequency, as in 24 beats per second (assuming a 2 blade shutter) I would check the flicker blade on the shutter to make sure no holes have been burned in the blade.

Seeing the problem is occurring on BOTH machines, that would indicate a common item between the two machines, something like your incoming power supply.

I have also heard of lenses loose in the mounts were vibrating and distorting the image and this was misreported as flicker.

Posted by Marin Zorica (Member # 1716) on 03-14-2010, 07:12 PM:

Vibrating and so isn't problem, because all is seating tight and clean. A powering could be any reasonable thing to point now, as I didn't measured, but sure all 3 phases are there. Only, I did saw sometimes situation with voltages ph1=210, ph2=245, ph3=230 and still no problem in flickering....

I did also check shutter but on hurry, as I didn't saw any damage on it.

Posted by Louis Bornwasser (Member # 3063) on 03-14-2010, 08:00 PM:

In 60 Hz countries you get a 12 Hz difference. In 50 Hz counties you get a 2 Hz difference. Could be incoming power (as states) or counld be unmatched diodes. IREMs are "sensitive" to diode mismatching. Louis

Posted by Tony Bandiera Jr (Member # 2365) on 03-14-2010, 08:46 PM:

I think he may just have the image too bright, 1600w on a roughly 25' wide screen could cause flicker with a two-blade shutter.

Martin, try de-focusing the lamps slightly to lose a bit of light (which would also flatten the field a bit too.)

Also, 55 amps is a bit low for a 1600 watt lamp. Try bumping the current up to 60-65 amps, see if the flicker goes away. If that makes the image too bright then do the de-focus trick.

Posted by Demetris Thoupis (Member # 833) on 03-15-2010, 01:45 AM:

Nope. I had the same thing and it ended up it was the diodes in the rectifier!! It wasn't exactly a flicker but it was something like dimming the light up and down while the projector was running.
Demetris

Posted by Marin Zorica (Member # 1716) on 03-15-2010, 06:07 AM:

I don't think is diode, since there is no slowly fading or so, flickering is fast and not so big.....and is hard to be same thing on both.

Also this isn't IREM, is old rectifier but with 6 new diodes in it, and other machine where rectifier was before did run good.

Will try to get lamp out from focus, but before will measure AC ripple on output.

Posted by Marin Zorica (Member # 1716) on 03-19-2010, 03:33 PM:

I did measure AC ripple, below 5%, also did try to add 4700uF capacitor to rectifier, but is same......so probably is something on this V5's shutters?

Posted by Monte L Fullmer (Member # 2797) on 03-19-2010, 08:24 PM:

I'd call it the bulb focus issue - back off the bulb some. It's nice to have a bright light, but you can have it too bright.

-monte

Posted by Mike Croaro (Member # 3123) on 03-19-2010, 10:42 PM:

If the screen is 25 feet wide (presumably 25 X 11 for scope) I can't imagine the 1600 watt lamp is putting too much light on the screen. Am I missing something?

Mike

Posted by Tony Bandiera Jr (Member # 2365) on 03-20-2010, 01:52 PM:

Mike, you are missing something. [Smile]

With a two-blade shutter a 1600w lamp can easily cover a 30' wide screen (maxed out though) and meet SMPTE standards.

Of course this is with a properly aligned lamphouse and good quality lenses.

At UC Irvine, with Kinoton lamphouses, my 1600 watt lamps, running at 1550 watts, with a three-blade shutter, gives me 16.5 fl on flat and about 20 fl on scope if I don't adjust the current. Our screen is 28' wide in scope.

Most never screens have at least some gain to them..the old charts and recommendations were often based on a "zero-gain" screen.

Posted by Mike Croaro (Member # 3123) on 03-21-2010, 12:30 AM:

Hi Tony:

My experience is likely outdated. I last worked in theatres 12 years ago. And it was always with old lamphouses, older lenses, older screens etc.

Mike

Posted by Tony Bandiera Jr (Member # 2365) on 03-21-2010, 02:44 PM:

Mike, don't feel bad--it has been years since I have worked in an actual theatre as well since I have been working on screening rooms almost exclusively.

I think it was ISCO that had a "bulb sizer" on its slide-rule lens calculator, it always seemed to call for a way oversized bulb..but it was valid for three-blade shutter setups.