Film-Tech Forum ARCHIVE: Xenon Lamp set up for newbe

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Posted by Tony Smith (Member # 7191) on 05-04-2015, 11:34 AM:

Hi Folks
Still contining with the refurbishment of the Cinemeccanica Portacine 35X.
Have been projecting short film run, look very good, but I think the lamp xenon 500 watt short arc, running on rectifier at 17 volts
dc at 28 amps(Position 4 of 7).

The lamp has a bright roundish section near the left hand side.
otherwise quite good, we have taken the lamp out, not changed any of the - negative end mechanical settings at all yet, so is just a matter of turning the lamp to the right?

Still finding our way around this lot, any help would be nice please

Tony Smith

Posted by Leo Enticknap (Member # 534) on 05-04-2015, 01:02 PM:

If you can't see any obvious defects on the mirror (e.g. pitting), it should just be a question of tweaking the mirror alignment to get rid of the hot spot. This has to be done every time you change or rotate a bulb anyway, because the flame of the new one never settles in exactly the same position as its predecessor.

Posted by Frank Cox (Member # 6258) on 05-04-2015, 02:06 PM:

My method for focusing a xenon lamp:

Remove lens from projector, start lamp and projector to get white light on the screen.

You will see a large black spot and a smaller black spot on the screen. The objective is to move the lamp around such that the large black spot is centered on the screen and is as small as possible, and get the smaller black spot centered behind the large black spot. Move the lamp toward and away from the projector makes the spot smaller, and moving it up and down and side to side does the rest.

That will get you really close to where you want to be.

After that's done put the lens back in and tweak the settings so the light is as bright and as even as possible across the screen.

Posted by Tony Smith (Member # 7191) on 05-04-2015, 04:04 PM:

Hi Both
Thank you very much for your replies.
Will certainly give that a try.

Tony Smith

Posted by Frank Cox (Member # 6258) on 05-04-2015, 04:51 PM:

When you're working on this with the lens in place, don't run the light through the lens continuously for great periods of time. Work on it for 30 seconds or so, then close the dowser and let the lens cool off for a minute, then open the dowser and continue.

Running white light through the lens for a long period without allowing it time to cool down can do bad things to your lens.

If you've done the part with the two black spots correctly, it should only take a few seconds to fine tune it with the lens in place anyway.

Posted by Tony Smith (Member # 7191) on 05-05-2015, 10:31 AM:

Hi Frank
Thanks for your info, will remember this

Tony Smith