8mm Forum: ST1200HD Pressure Plate

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Topic: ST1200HD Pressure Plate

Dan Lail
Film God

Posts: 2110
From: Loganville, Georgia, USA
Registered: Jun 2003

posted December 17, 2003 01:36 AM

Hi, all, I have an ST1200HD with a focus problem. The ending of a reel of film tends to focus differently than the beginning and middle of the reel. Would this be the pressure plate springs not pressing the film flat at the end of a reel of film where the film is more curled? I don't have this problem on my ST800. Where can I get new springs?
Thanks for any info. [Confused]

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Barry Johnson
Master Film Handler

Posts: 358
From: United Kingdom
Registered: Jul 2003

posted December 17, 2003 04:13 AM

A little known fact that affects all projectors of any gauge including 35mm/70mm is that during use,they actually expand!
This is attributable to the heat generated from the lamp source,and the heat energy created by the motors.
Even theatrically,focus has to be checked (or should be!) during the course of a film..............
If you wish to put the blame on to the print then yes,it has a small (very) effect due to how it forms when rewound/stored etc.

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Standard8 rules!!

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Dan Lail
Film God

Posts: 2110
From: Loganville, Georgia, USA
Registered: Jun 2003

posted December 17, 2003 01:04 PM

Thanks, Barry, but I don't have this problem with the ST800. Also, this problem exist with any print I run on the ST1200. It's not a slight focus variation, but rather a substantial focus change. Anyone know where to purchase new springs.
Dan [Frown]

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted December 17, 2003 06:53 PM

Hi Dan,
Now this is very difficult to explain to you but I have seen this on Elmos before and it can be caused by the "strip spring" which presses against the back of the lens. I think that with some older machines the focusing assy can become worn with use and then the focus knob becomes quite slack instead of stiff if that makes sense?
If you remove the lens and look down the lens holder you will see the "strip spring" I am talking about.
To check this out simply undo the cross head screw at the back of the lens holder which holds the spring in place. The spring is under the lens holders back plate, and then remove the spring. This will mean that you dont have the back pressure from the spring pushing against the rear of the lens. Focusing is less smooth but it might help your focus problem. If this isnt the case then you can put the spring back. Try not to undo all four screws on that back plate other wise the plate may go out of position. At least leave one undone.

Kev.

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GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Dan Lail
Film God

Posts: 2110
From: Loganville, Georgia, USA
Registered: Jun 2003

posted December 21, 2003 06:32 PM

Thanks, Kevin. I removed the spring and the focus from border to border improved, but I still have to tweek the focus about 85% of the way through a reel. I'm going to store a reel of film wound tails out for a while, then run it and see if that helps.

Merry Christmas to all across the pond. [Smile]

web page

[ December 21, 2003, 10:32 PM: Message edited by: Dan Lail ]

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted December 22, 2003 01:04 AM

Definately worth a try then. Hope it helps.
Have a good Christmas from us across in the UK. [Smile]

Kev

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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