This is topic Dolby reader shedding in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Richard Miller (Member # 1405) on 08-22-2002, 07:47 PM:
One of our Dolby Digital readers sometimes makes a slight clicking noise. When it does, it seems the film sheds a lot. Even when we run Filmguard it doesn't help. The problem only happens occasionally (about once a week) and no one can seem to figure it out. All the pad rollers are clean and the sprocket teeth are fine. Any help with this problem is greatly appreciated.
Posted by Wes Hughes (Member # 981) on 08-22-2002, 08:33 PM:
Perhaps you are sometimes running with too much tension on the reader drum ??????
Posted by Mark Gulbrandsen (Member # 72) on 08-22-2002, 10:27 PM:
Check the tension, and also check the inside flange of the lateral guide rollers in the tight loop system. I've been seeing some ugly looking ones in various places lately.
Mark
Posted by Randy Stankey (Member # 64) on 08-22-2002, 10:29 PM:
Too much tension or not enough.I'm sure you know about the white 1/2 circles, right? The arms that hold the idler/tension rollers must line up with the two circles on the back of the bulkhead. If the film is too tight it will pull th ese rollers/arms too far apart. The tension will damage the film as it gets pulled along the teeth of the main sprocket. Not enough and the idlers will rub together and the film will touch together too.
You may also have a worn, damaged or loose pad roller or idler roller. In which case the roller may occasionally move out of position and pinch or rub the film the wrong way. It may even pull the film out of line so that it gets scuffed along the edges as it goes by the offending roller.
Check your threading practices and see if that's the cause. If that's not it then go through the unit and check all the rollers to see if the are tight and aligned properly.
Fail that... you may have a film path irregularity somewhere else in the system, such as at the platter. As the film goes through the Dolby reader the dust is being "thrown off" as it goes through. It is the first place in the path where the film goes through a series of rollers/sprockets. The dust in the reader may be a symptom of a problem somewhere else.
Posted by Richard Miller (Member # 1405) on 08-22-2002, 10:38 PM:
I hope it's not the threading, the other two are always ok. I know the white half circles are in alignment everytime. I guess I'll try checking the tensions in the morning.
Posted by John Pytlak (Member # 331) on 08-23-2002, 09:42 AM:
Sounds like you either have incorrect tension, causing the sprocket teeth to "pick" at the perforations, or misalignment causing scuffing of the edge of the film.------------------
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 Rick Long (Member # 213) on 08-23-2002, 10:27 PM:
Had a similar complaint of shedding coupled with a ticking sound. As Mark states, the cause was due to a burr on the film side of the roller flange. Filed it smooth, no more problem.
Posted by Paul G. Thompson (Member # 655) on 08-24-2002, 04:07 AM:
What kind of sprocket does it have? Cinemechanica or LaVezzi?