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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » Zenith ZX4000H too Dark (Page 1)

 
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Author Topic: Zenith ZX4000H too Dark
Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-22-2005 05:48 AM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
A cinema was upgraded some years ago to the above mentioned lamphouse. Even though the installer did a damn good job in putting the damn thing on a V8 projector (really old) and getting all the distances e.t.c exactly as they are in the manual, the damn picture is too dark even though it is projecting with an USHIO lamp of 4kw at 135A (rated amp). I've cheked the lamphouse and it looks straight in the middle (lamp to gate). Checked it through the lens holder, put a damn laserpointer thingy e.t.c, dummy bulb e.t.c but still the immage is too dark. It looks straight but when the film is running and watching the light through the green glass (where the shutter is) the light seems to be hitting offset left. Any ideas?
D

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Richard Fowler
Film God

Posts: 2388
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001


 - posted 06-22-2005 09:49 AM      Profile for Richard Fowler   Email Richard Fowler   Send New Private Message       Edit/Delete Post 
We have had problems with the clamp ring not seating the reflector to the support casting or the casting and or bulkhead supporting the casting not being square. Laser check of the reflector with reference from front and rear.....what laser tool are you using?

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Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-22-2005 10:26 AM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
It's something out of the local market that measures distance in exact e.t.c. Its not one which fits in the middle of the lens

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Thomas Jonsson
Expert Film Handler

Posts: 216
From: Bromolla, Sweden
Registered: Sep 2003


 - posted 06-22-2005 03:35 PM      Profile for Thomas Jonsson   Author's Homepage     Send New Private Message       Edit/Delete Post 
Had the same problem a year ago when a tech was here and
replaced the old reflectors with new ones. Light wasn´t
good, and he couldn´t figure it out. So he opened up the
lamphouse again and started to "twist and turn" the reflector
and suddenly -pop- it fell into place. And there was light...

Thomas

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System Notices
Forum Watchdog / Soup Nazi

Posts: 215

Registered: Apr 2004


 - posted 06-03-2007 09:09 AM      Profile for System Notices         Edit/Delete Post 

It has been 710 days since the last post.


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Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-03-2007 09:09 AM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
Ok bringing the topic back. After a lot of trials, alingotron alingment, and a lot of fiddling around I have discovered that when I open the dowser without the projector running, we have enormous amount of light in both flat and scope lenses, the bulb is dead centre and the light is amazing. Now... When we do start the projector though, and the shutter starts running, the light drops to a very dark level as if 50% less than what we was seeing. Any ideas?
Demetris

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Brad Miller
Administrator

Posts: 17657
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 06-03-2007 01:28 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Dumb question, but are you aware that the purpose of the shutter is to block the light during the pulldown action of the intermittent? Think about it for a minute.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002


 - posted 06-03-2007 01:42 PM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
Not a dumb question at all in this context since I am a little bit surprised by Demetris' observation - of course, the shutter takes away roughly 50% of the light energy - but it also has to be pointed out that the lamp should not be run for more than a brief moment with the projector standing!!! That can easily heat damage the projector head.

One thing it seems Demetris has not checked is if the working distance is correct, and if the reflector has the correct size for this lamphouse and lamp type. Or maybe he did, it is not entirely clear from the above posts. If we assume it is, then the only other factors really are that the reflector coating might be bad and then the actual alignment itself. Aligning with a laser tool is a good first step, but it needs to be checked if the image of the reflector on the screen is really centered and symmetrical - otherwise, the reflector is not properly aligned to the gate. That can be visually checked on the screen with the lens removed. Then the lamp really has to be centered in the middle of the hole, and the arc an end pieces have to be on a straight line. One good way to check all that is to move the lamp all the way forward and see that it stays centered in the middle of the hole. The reflector image also has to be perfectly round with the hole centered (remove the aperture plate to see as much of it as possible) and also, when the lamp moves forward, you get to a point where you see concentric rings appear on the reflector. These rings have to be even and appear and disappear at the same time on all sides. Otherwise, the reflector is not properly aligned.

Another great tool to help with that is the Kinoton alignment beamer, but if that is not within reach, obviously it won't help too much.

It also needs to be known how big the screen actually is, if it has top or side masking, what gain factor it has, and what the specs for this lamphouse regarding screen sizes are.

Finally, Demetris said something about the light hitting off center in the first post. When you look into the view port, you do indeed see the light off center on the reflector as you are looking at the whole assembly from an angle. But the arc itself has to be centered and straight between the electrodes, otherwise the magnet alignment has to be checked. Or were you talking about watching where the light hits in the gate area? If that appears to be off center, then there is defiitely a physical alignment issue. Using laser pointers for alignment may not be the best idea here. Visual alignment as decribed above is actually better then.

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Christos Mitsakis
Expert Film Handler

Posts: 242
From: Ag.Paraskevi, ATHENS, GREECE
Registered: Sep 1999


 - posted 06-04-2007 04:35 AM      Profile for Christos Mitsakis   Email Christos Mitsakis   Send New Private Message       Edit/Delete Post 
Is it a barrel shutter? May be the centrifugal flaps are burned and aren't opening at full during operation.
C.

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Hugh McCullough
Expert Film Handler

Posts: 147
From: Old Coulsdon, Surrey, UK
Registered: Jan 2003


 - posted 06-04-2007 06:06 AM      Profile for Hugh McCullough   Author's Homepage   Email Hugh McCullough   Send New Private Message       Edit/Delete Post 
Just a thought, but When the projector is running is the fire/safety shutter, the one you push in by hand, staying fully locked into position?

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Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-04-2007 11:24 AM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
Ok Guys,
I've been doing this since 6 so I do know the purpose of the shutter and I do know how to properly aling a lamphouse as I've done it not only on Cinemeccanica all the old models with the original pedestals and custom made brackets to install the lamphouse on, but also on Microtechnica, Prevost, Kinoton with excellent results and I never had this issue. I allinged three other V8's with smaller lamphouse and never had this issue but what this thing is doing is very strange. The distance of the reflector to the gate is exactly as it is in the installation manual. The lamphouse and reflector is centered and I am 100% sure of that. The shutter is blocking too much light to the point of darkening the image too much. It is a conical disc shutter double bladed. I have only left the projector open for a few seconds without it running just to make a comparison. I did not just left a 4k bulb heating the projector in iddle mode. The reflector image is perfectly round and when the lamp is pulled backwards or forward then the light evenly darkens on the corners. I have never seen this happen to any of the projectors we have here before. The lamphouse is alinged based on the manual. I installed the same lamphouse on a V5 running at 2.5K and the light is far better than this one when running. The dimming of the light on the screen when the projector is running is too much and is not appropriate.

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999


 - posted 06-04-2007 01:34 PM      Profile for John Walsh   Email John Walsh   Send New Private Message       Edit/Delete Post 
So, this is really a projector problem since you had the lamp on another projector (a V5) and it worked OK.

Hugh's idea regaring the fire/safety shutter is a good one .. I forgot about safety shutters because sadly most projectors today don't have them.

I never heard of a projector with a double bladed conical disc shutter. What make is it? Anyway to verify they are in sync?

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Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-04-2007 01:51 PM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
John sorry for the missunderstanding. I meant that I installed the same type of lamphouse on an old V5 with excellent results. This was brand new from the factory. What do you mean in sync? If you mean timed correctly with the intermittent yes it is as there is no ghosting on the image.
Demetris

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002


 - posted 06-04-2007 01:56 PM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
quote: Demetris Thoupis
Ok Guys,
I've been doing this since 6 so I do know the purpose of the shutter and I do know how to properly aling a lamphouse as I've done it not only on Cinemeccanica all the old models with the original pedestals and custom made brackets to install the lamphouse on, but also on Microtechnica, Prevost, Kinoton with excellent results and I never had this issue.

OK, then you don't need our input here. You already know everything. Sorry for wasting your time.

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Demetris Thoupis
Phenomenal Film Handler

Posts: 1240
From: Aradippou, Larnaca, Cyprus
Registered: Apr 2001


 - posted 06-04-2007 02:14 PM      Profile for Demetris Thoupis   Email Demetris Thoupis   Send New Private Message       Edit/Delete Post 
If I did not need an input I wouldn't be bringing up the post again. I don't like to brag but I believe I am quite competent technician and I managed to overcome a lot of issues especially with old projectors still in service. What is happening in this case is something I cannot undestand that is why I am asking whether someone has anything they might want to add. In the past, on this projector there was the Zenith X4000 vertical lamphouse and we never could get a descent light out of it so we decided to go with a new horizontal lamphouse and it was our saddness when we witnessed the same result. We have a Victoria 6 also in this theater with a 2.5 K bulb on a Zenith 3000H and is brighter than this one. I have a head from a closed cinema of a V8 on which we never had issues and I am thinking of changing the head to see if something will get better. But in the meantime I would really like some help considering that the lamphouse is alingned, with correct bulb adaptor.

Hugh, the film/safety shutter stays fully locked in position.

Demetris

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