Film-Tech Forum ARCHIVE: Gate Tension

This is topic Gate Tension in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=003673

Posted by Brent Arnold (Member # 1152) on 07-03-2002, 04:46 PM:

My image seems to be going back and forth (from the right to left and back) and I was wondering if this is a problem with the gate tension. I realize that it is a problem with static, probably, but I am wondering if adjusting the gate tension will help. And if it will how do I fix it (By the way I have an old century projector... not sure what year, but it is old)

Thank You.

Posted by Brad Miller (Member # 2) on 07-03-2002, 04:50 PM:

Static has nothing to do with it. Gate tension for the most part does not either. (Too much can aggravate it.) Your problem is with the lateral guide roller right by the framing window. The soundtrack edge roller should not move, whereas the picture edge roller SHOULD have a spring action. Overall they need to spin freely as well. Is this a problem with one particular print? If so, which one? Check that and report back.

Do note that if the roller is improperly adjusted you can cause the image to be off center or you could end up showing the edge of the film on the screen. You could also make the problem worse. If you've never adjusted this before, you are best off letting your tech come in and show you how to do it.

Posted by Scott Norwood (Member # 30) on 07-03-2002, 05:50 PM:

For the sake of completeness, I'll explain how the gate tension adjustment works on Centurys, although, like Brad said, this won't help the problem described.

Newer 35mm Centurys have flexible bands in the film trap; the gate presses the film against these bands and tension is set by adjusting the tension of the bands. This is set using a smallish knob (usually with a numbered scale) at the top of the trap. This is very similar to the same adjustment on a Simplex X-L or PR1014.

Older Centurys (Cs and early SAs) don't have the flexible bands, but instead have _two_ adjustments on the gate itself, one each at the top and bottom of the gate.

Older JJs don't have flexible bands either; the tension adjustment is a knob on the gate, to the left of the large knob that one uses to open the gate. This is the same location as the thumbscrew in 35mm Centurys that one unscrews to remove the gate for cleaning.

I don't know about newer JJs; maybe someone else does.

Posted by Paul G. Thompson (Member # 655) on 07-03-2002, 05:53 PM:

Check your lateral guide roller in the top of the gate assy. It might be sticking or just out of adjustment. A good cleaning may correct your problem.

Posted by Gordon McLeod (Member # 33) on 07-04-2002, 07:53 AM:

Pull out the apperture and looke at the projected image of the perfs
That will tell you quickly if it is the print or the machine If the perf edges are steady it isn't the machine

Posted by Daryl C. W. O'Shea (Member # 1303) on 07-05-2002, 03:21 AM:

If you can't see the perfs when you pull out the apperture (the best way to tell), check to see if your trailers and rolling stock are steady or moving around. If these are steady then it's probably the print and not the machine.

Posted by Gordon McLeod (Member # 33) on 07-05-2002, 06:49 AM:

Don't trust trailors or rolling stock as they could have defects as well. Use the perf or SMPTE 35PA
Just pull the plate

Posted by John Pytlak (Member # 331) on 07-09-2002, 01:06 PM:

I agree that the best "test" of projector steadiness is to pull the aperture so you can see the edges of the print perforations (usually along the far right side of the projected image). If the actual perforations on the print are "rock steady", your projector is doing its job in projecting a steady image.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Daryl C. W. O'Shea (Member # 1303) on 07-10-2002, 12:07 AM:

I totally agree that pulling the plate is the best thing to do. However if you are unfortunate enough to have top masking it can be often difficult to make out the perfs on the masking even with all the lights off in the theatre. It becomes especially difficult if the perfs are projected into the corner of the wall.

Posted by John Pytlak (Member # 331) on 07-10-2002, 09:11 AM:

If you can't shift the projector/masking to project the perfs on the regular screen, set up a portable "screen" (e.g., large piece of cardboard) close to the projector and focus on it to observe any movement of the perfs.

Posted by Mike Jones (Member # 522) on 07-12-2002, 12:08 PM:

I agree with the weenie man, probably a sticky lateral guide roller. those other metal guides usually don't move, and therefore probably don't need adjustment. but, give it a look.

word,

Mike

Posted by Wes Hughes (Member # 981) on 07-13-2002, 10:56 PM:

I would check for worn or improperly adjusted studio guides.