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This topic comprises 2 pages: 1 2
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Topic: need advice on xenon alignment?
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 03-27-2002 08:43 AM
And once you do all those things....use the string, use the big stick with the thing that sticks in the lens holder, and you get that round black spot to sit perfectly centered on the screen when you have the lens out, xenon lovers will make it sound like that will get you a completely even, corner-to-corner light. Well, my friend, that would only be true if you were aligning a CARBON ARC lamphouse. With xenon, you may have to resign yourself to settle for uneven light, mottled with dark spots and hot spots that just move around the screen while you twist and turn the alignment nuts until you're blue in the face. I mean, how much "alignment" can you do with a lamphouse that can only sit one way on the pedestal? Either the screw holes in the lamphouse line up with the slots or they don't -- it's not like you have any fine adjustments left and right. The only thing you can really adjust is the distance from the center of the bulb to the center of the aperture plate. And believe me, you can have that distance correct down to the millimeter and that won't guaranttee you anything in terms of no hot spots or dark corners. And lastly, don't fall into the trap of thinking, "Oh, geez, I must be doing something wrong....it must take a 'tech guy' to align this" HAH! You ARE the tech guy. What...you think he's got some magical powers that you don't have? He knows some special "tech controls" in the belly of the lamphouse that's gonna make it put out an even, beautiful light? Maybe in some mythical world, but when it comes to xenon, I'll bet you're pretty much are doing it all right -- it's just a crappy lamphouse. IT AIN'T YOUR FAULT! (See what happens when I log on before I have my morning coffee?)  Sorry guys. Frank
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Dave Macaulay
Film God
Posts: 2321
From: Toronto, Canada
Registered: Apr 2001
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posted 03-27-2002 08:52 AM
The SLX uses the little pin clip to set the height of the yoke, and it usually comes close to being correct if you use the right hole. The Ushio CX16 is physically the same as the Osram 1600HSC and uses the brass threaded-on cathode adapter and the chrome anode extension, correct?
For this setup the pin must be in the bottom hole - thus the yoke is at its highest "preset" position. (page 12 in the newer SLX manual)
Unless the lamphouse has been maladjusted via the threaded rod inside, or it has a new type adjustable mirror that has been maladjusted, this should give a well centred beam right down the design axis.
Try removing the main lens and aperture plate and projecting white light on screen (motor running!). With the cathode adjustment roughly centred you should be able to get a basically circular pattern with the light brightness symmetrical around the centre, excluding the cable shadow. That happens when the lamp arc is centred in the (properly shaped and not bent or dented to hell) mirror and near the focal point. If the cathode adjuster is right at one edge to do this, you can move the anode yoke the same way to correct it. Up is easy, down you remove the pin, sideways you turn the yoke so it isn't perpendicular to the mirror. Don't get anal about the cathode being perfectly in the centre of its adjustment.
The centre of the round light pattern on screen must be very close to the centre of your scope screen. The 1.85 masked screen area may be off center depending on what masking edges move but the scope area is the important one for this. If it isn't centred - the lamphouse is misaligned with the projector head.
If you have the lens and mirror adapters and want to use the string method give it a try.
An important thing to remember is that the aperture is one of the alignment points.
The string reflection should match the string image all around, with the string passing through the centre of the film aperture. The old fixed mirrors made this hard to screw up, the new adjustable one lets you get the string looking good with the lamphouse axis offset to the projector optical axis.
The aluminum yoke adapter thingy for the string method is pretty useless for setting the yoke, but handy for aiming the adjustable mirror. The string should look "right" in the mirror, and go through the centre of the yoke adapter hole with the yoke square to the mirror and set with the pin in the bottom hole (highest yoke position!). Then align the lamphouse and projector without changing the mirror settings.
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