Film-Tech Forum ARCHIVE: Lamp alignment, Y axis issue.

This is topic Lamp alignment, Y axis issue. in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Gronw Roberts (Member # 9141) on 07-25-2018, 10:58 AM:

My co worker changed the lamp (Ushio DXL-40SN2) on our NEC NC2000C a few days ago while I was off work. He mentioned that the lamp alignment needed a lot of tweaking and that I should check it. It seems that the Y axis bolt has been adjusted as much as it will go but the figures suggest that it still needs more adjustment, they still want to climb.

I had a look at the lamp and it does seem to be sitting at an angle, the cathode end is higher than I remember, I've never noticed that before and I've never run out of adjustment on the X,Y,Z bolts.

I want to re seat the lamp (I can't imagine he got it wrong though, he's very capable) to see if it helps but I have to wait for two of us to be here due to health and safety rules.

As far as I can tell the picture seems fine, but I've never come across this before. Is this familiar to any of you?

Posted by Leo Enticknap (Member # 534) on 07-25-2018, 06:55 PM:

I've encountered at least one NEC in which the height of the stand that holds the cathode end of the bulb is adjustable, and is clamped in place by a grub screw. Is it possible that it could have slipped, with the result that the bulb is now pointing downhill?

Posted by Dave Macaulay (Member # 813) on 07-26-2018, 12:09 AM:

Probably the anode end is sitting too high for some reason, otherwise the folding mirror may have been moved somehow?

Posted by Steve Guttag (Member # 268) on 07-26-2018, 07:01 AM:

If this happened right at the lamp change, I don't suspect the projector. Quick check, rotate the lamp 180 degrees and re-align. If it changes a lot, then the lamp is clearly out of round (electrodes with respect to the stems) and a warranty defect should be claimed. If the light is similar, then something is indeed amiss.

For one, DON'T use the NEC light meter. It will mislead you. Put up a white pattern and adjust for it to be as bright AND as even as possible. You can use the meter after that, often but even then what it says is best is more often than not worse than by eye and external meter.

Posted by Leo Enticknap (Member # 534) on 07-26-2018, 10:44 AM:

Sorry; I meant to write anode end (not cathode) above.

Agreed on the NEC auto alignment tool - if you follow its numbers, you'll end up with a humongous hot spot. The Barco one is an order of magnitude better.

Posted by Gronw Roberts (Member # 9141) on 07-26-2018, 10:45 AM:

Thanks. I'll rotate the lamp and see what happens.

Posted by Gronw Roberts (Member # 9141) on 07-26-2018, 12:46 PM:

Rotating and re seating the lamp sorted everything out. There's plenty of room left on each of the axis adjustments now, I'm feeling much happier about it.

Thanks for your help everyone.

Posted by Steve Guttag (Member # 268) on 07-26-2018, 03:27 PM:

quote: Leo Enticknap
Agreed on the NEC auto alignment tool - if you follow its numbers, you'll end up with a humongous hot spot. The Barco one is an order of magnitude better.

Yeah, Barco got the light meter right as well as allowing one to have separate files for each format (lens zoom). Christie got the auto lamp alignment right (Barco takes forever and is often worse than just doing it by hand). NEC...well...one gets to relive the sloppiness of the old Christie H console adjustments. All they need to do is use nylon gears that disintegrated under the UV light from the xenon to make it complete.