Film-Tech Forum ARCHIVE: Dolby reader shedding

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Topic: Dolby reader shedding

Richard Miller
Film Handler

Posts: 33
From: Lafayette, IN, USA
Registered: Aug 2002

posted 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.

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Wes Hughes
Expert Film Handler

Posts: 175
From: Raleigh, NC, USA
Registered: Aug 2001

posted 08-22-2002 08:33 PM

Perhaps you are sometimes running with too much tension on the reader drum ??????

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 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

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 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.

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Richard Miller
Film Handler

Posts: 33
From: Lafayette, IN, USA
Registered: Aug 2002

posted 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.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 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

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Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 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.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 08-24-2002 04:07 AM

What kind of sprocket does it have? Cinemechanica or LaVezzi?

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