8mm Forum: Elmo st-1200 jitter

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Posted by Norman Fisher (Member # 481) on July 19, 2009, 09:48 PM:

Hi gang, My ST-1200HD picture has started to "jitter" up and down during projection, and it's getting a bit annoying. I replaced the belts and it didn't seem to help. Cleaned the guides, and still nothing. Never have had this problem before. I have an ST-800 too, and the films play perfect on it. Any ideas what might be the culprit and how to fix it? Much appreciated! Thx!

Posted by Dino Everette (Member # 1378) on July 20, 2009, 02:20 AM:

Have you checked gate tension or your loop size since those usually are the first things I think of regarding jitter? I actually had a similar problem with an ST-1200 HD that I recently acquired and it was caused by the latch for the lens/gate assembly when it swings and snaps into place. It was just loose enough that it wasn't keeping the film smooth and tight as it passed through. I bent it back a tiny bit so it would provide a tighter grab and that was all it took on mine, hope yours is an easy fix like that.

Posted by Norman Fisher (Member # 481) on July 21, 2009, 09:07 AM:

Thanks Dino! No I have not checked the gate tension. I will do so when I get home from work tonight. [Smile]

Hope that's the answer!

Posted by Kevin Faulkner (Member # 6) on July 21, 2009, 05:18 PM:

There is one or two other possibilities which spring to mind but try the easy one from Dino first.

One is that the cam itself needs greasing and the other is that the plastic round piece that runs in the cam has got worn. But thats another story and not until you have checked the obvious.

Did this suddenly start to happen and does putting any lube on the film itself help? The Elmo's dont like dry or green film. Try running the film through a cloth with some film lube while the film is running to see if it stops the problem. I know you say the same films run on the ST800 ok but these machines all have their own inbuilt personalities.

Kev.

Posted by Tony Stucchio (Member # 519) on July 21, 2009, 07:12 PM:

I would also decrease the tension on the take-up reel. This is sometimes a problem -- if it is too strong the lower loop is lost very easily.

Posted by Roy Neil (Member # 913) on July 22, 2009, 04:47 PM:

Tony - I had a similar problem with losing the lower loop on autothread with an ST-1200HD I was repairing.

Decreasing the takeup tension will prevent the film from being 'yanked' and cure the symptom but introduces a new problem with takeup on 1200' reels due to insufficient tension.

The 'real' problem is the small torsion spring that pushes the green plastic guide against the lower sprocket - if this spring is out of its 'slot' or not providing sufficient tension, the film can be 'yanked' through the sprocket causing the lower loop to be lost. Tensioning the spring tighter will eliminate the problem and allow for a firm takeup tension.

Posted by Jon Addams (Member # 816) on July 22, 2009, 11:41 PM:

Hi,

Just how one does decreases the take-up’s tension?

Thanks

Jon

Posted by Tony Stucchio (Member # 519) on July 23, 2009, 07:06 PM:

Take the back cover off. While holding the takeup spindle, on the outside of the machine, rotate the knob (connected to the gear that turns the spindle) on the inside of the machine counter-clockwise.
It takes some trial and error to get it to where there is not too much tension, but not too little that you wind up with a floor full of film for a 1200 footer.

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