Film-Tech Forum ARCHIVE: Floating focal point... still there

This is topic Floating focal point... still there in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Dan Chilton (Member # 2288) on 02-24-2007, 11:16 PM:

The focal point on my lamp (1.6k Orc) keeps moving around. I originally mentioned it here, but after trying all those things, it never seemed to rectify itself. I know it's a crappy lamphouse, which is why we're upgrading to a newer 2k Xetron next week, but the problem still perplexes me.

I made a quick flash animation to demonstrate the problem... here.

It only does it on certain occasions, but I can't figure out why, or what might be causing it to bounce around from side to side. When it does, I pull the bulb focus out so it's not quite as noticeable. The bulb's tight, contact connection is good, no magnets near the reflector. It's done it one two separate bulbs (both Osram), so I don't think it's that.

Also, we're a single screen, so don't ask me if my other lamphouses have the same problem... because there are none. I'm sure I won't care once I get the Xetron in, but it's bugged me for the last year and a half. And if I were to take a guess, I'd say it floats 1 out of every 25 shows. Turning the bulb off seems to help a little, but usually the problem just comes and goes as it pleases. Any suggestions/guesses on what might be causing this?

Posted by Mark Gulbrandsen (Member # 72) on 02-25-2007, 01:06 AM:

quote: Dan Chilton
I know it's a crappy lamphouse, which is why we're upgrading to a newer 2k Xetron next week

Truthfully... its debatable which one is the crappier, the old Xetrons are nothing to write home about either but at least you can get an excellent mirror retrofit from Big Sky for them so you get more than match light out of it. Some of the old IREM ignitors are crappy too with cases splitting open and flames comming wenchforth!! I had one go bad last week.

On the ORC check the allen screws(three I think) that secure the mirror support to the center divider wall. Some times these screws come loose and things can drift around. There are cup type washers under those screws that actually provide some loading against the wall so things can't slip. Be sure NOT to overtighten those screws too much or you won't be able to move the X/Y adjustments at all. Hope this helps.....

Mark

Posted by Gordon McLeod (Member # 33) on 02-25-2007, 07:50 AM:

Also I have seen some with the lid on backwards and the airflow was screwed up causing a very unstable arc. Also I have seen people use the wrong serries lamps with adapters and as such they need magnetic stabalization
Also I think you have a lot of hotspoting which will make it more noticable if your animation is acurate

Posted by Dan Chilton (Member # 2288) on 02-25-2007, 11:51 AM:

Hotspotting? What is that, and how can I check if I have it / correct it?

Posted by Gordon McLeod (Member # 33) on 02-25-2007, 01:19 PM:

If there appears to be a bright ball of light in the centre of the screen compared to the edges that is a hot spot

Posted by Louis Bornwasser (Member # 3063) on 02-25-2007, 03:06 PM:

What projector is used with the ORC? Ballantyne? Louis

Posted by Dan Chilton (Member # 2288) on 02-25-2007, 03:14 PM:

quote: Gordon McLeod
If there appears to be a bright ball of light in the centre of the screen compared to the edges that is a hot spot

It's always looked like that. Must be a hotspot... is that something that can be corrected?

@Louis: Our projector is a Simplex XL.