Elmo GS1200 400 W HTI upgrade ?

[Mikael Sundström]

My first post in this forum. *woohoo* Have been round here plenty of times but never signed up. This really is THE place for Super 8 discussion.

Yeah, well i visited the Wittner-Kinotechnik.de site the other day and found this 400W HTI bulb with coldlight reflector that would probably fit the GS1200 .. the biggest problems seems to be the price ..
and cooling... short arc bulbs get REALLY hot.. like glass glowing red hot.. and they contain a pressure of 10-25 atmospheres according to a text i read on a webpage somewhere... and they need a ballast to work.. ($$$)
Anyway most people won?t need a bulb THAT strong, but i figured since the 400W cost just as "little" as the 250W you might aswell take the 400W...

Again most people won?t need such an upgrade, only if you need real long throw. (auditoriums, drive-in Super 8 cinema !??)

I just love experimenting and building stuff.

Apart from brightness another advantadge over halogen is that these bulb are 5600K daylight bulbs. Then if you shoot daylight film to start with you can really get true projections. Not to mention they are flicker free. (At least flicker free by most peoples standards, even movie people... after what I?ve heard not all 'flicker free' bulbs and ballasts really are ... but that?s another thread altogether...) Wittner-Kinotechnik also sells a suitable ballast.

Just a thought.



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Mikael Sundstr?m

[Mikael Sundström]

I guess for overkill light output (if not already) you could add the rare f/1.0 12.5 - 25mm Elmo lens and if projecting at 24/25fps a 2-blade shutter.

Someday somebody will probably try and put in the XBO 500W Xenon bulb... that would REALLY be overkill.

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Mikael Sundstr?m

[#Pedro]

I think 400 W would not be much brighter on the screen than 250 or 270 W. The reason is that the spot diameter of the light has to be in relation to the gate size. Therefore a 250 W Halogen lamp is not brighter than a 150 W Halogen lamp.

I?ve just watched screenings with the 270 W HTI projector from Beaulieu. It?s no overkill for a screen-size of, let?s say from 2 meters and larger. The amazing thing is, that the colors are really natural and you can put a 16 mm machine with a 250 W halogen bulb close to the S8 projector and get the same screening results.

When screening CORRECT exposured films (most amateur S8 cameras produce over exposured films to compensate weak amateur projectors), that means light meter REALLY adjusted to 40 ASA, the result often seems very dark and needs an adequate projector. But then, you get deeper colors and more sharpness!

I would not consider to do a home-made convertion of the projector. There is a lot of know-how required, concernig the power supply and high-voltage starter block, the interferences with the sound amplifyer, the add. cooling and so on. I know that at Bavaria Munich they offer the HTI conversion for Beaulieu and Elmo.

Pedro

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[Mikael Sundström]

Ugo Grassi just mailed me and said something similar about the lightloss... that the spot diameter of the 400W version is 8mm ... while one frame is about 5.6mm wide, a lot of light will be lost ... at least the 250W is suitable since it?s spot diameter is 5...
But i was thinking ... since 250W and 400W bulbs are or almost identical, why not just change reflectors on a pair then or just put a weak condenser lens in front ? There must be a slight difference in shape between the two... if we could only squeez in 400W in those 5mm... (without burning up the film)

<BLOCKQUOTE><font size="1" face="Courier, Arial">quote:</font><HR>I would not consider to do a home-made convertion of the projector. There is a lot of know-how required, concernig the power supply and high-voltage starter block, the interferences with the sound amplifyer, the add. cooling and so on. I know that at Bavaria Munich they offer the HTI conversion for Beaulieu and Elmo.<HR></BLOCKQUOTE>

All true. Wittner-Kinotechnik sells good ballasts by the way...
I have read up on ballasts and on short arcs and schematica etc... the net is very helpful. I?m probably not going to do an HTI conversion in the nearest future.
But even if so, I think that with doing your homework (reading up thoroughly on your stuff) and using your common sense and caution you can actually pull it off.
There is not really that much DIY here it?s more a question of connecting 2 or 3 gadgets to eachother, the right way, without getting electrocuted, blown up or burned.
Dead serious of course.

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Mikael Sundstr?m

[ducter]

A few years ago i converted my Elmo GS1200 to the Osram 250W HTI lamp. The power
supply was built into an outside enclosure and this allowed for the projector to sit on top
of it and a 'special' set of HT leads (to feed the lamp) were able to be connected by a
a 'flying' lead that i had left out of the side of the projector. It was a difficult job to convert the projector. I think people tend to forget the amount of 'heat' these HTI lamps
generate plus the amount of UV light that they produce. I was warned by the supplier of the power pack and lamp of the steps to take and the dangers involved. I am an electronics technician so i was able to take on board what they were saying. All went well and the conversion worked out well. My temperature checks around the film gate
were within specs. The light output from the HTI was surperb and the power pack had the advantage of having a 'dimmer' control. However some weeks into using the projector
on one special screening i lost picture focus and it was'nt possible to restore it? I suspected the filmgate had warped but this was'nt the case. It was only after getting the projector home that i found the actual 'lens' had warped. (lucky i had a spare) I had never thought about the lens so i could only summarize that the amount of heat and UV had damaged the lens. I would caution anyone intending to convert to the 250w HTI to
fit a 'Hot mirror' (behind the filmgate) to reduce heat and UV. Since i have done this i have had no problems -i have however lost 10% of light output thru this mirror. I have to agree with a lot of the comments on the 400W HTI. Its just too big and dangerous for the GS1200. Anyone intending to convert beware of the massive 'heat' involved esp onto the lens.. T:thankU:he 'hotspot' of light given off by the 400W lamp just does not fit the 5.6mm
gate aperture and the remainder of the light\heat will just fry the gate plate..