Film-Tech Forum ARCHIVE: damaged Dolby Digital

This is topic damaged Dolby Digital - Cinemeccanica in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Antonio Marcheselli (Member # 373) on 06-28-2003, 07:17 AM:

HI everyone

I need your help... Here is the story from the beginning. When I worked in my one-screen theater I always had a problem: my two V5 (auto rewind) scratched the DD data in a strange way, as in the picture.

It was not a continuous scratch, I was not able to solve the problem but just minimize it adjusting all the rollers. At that time I thought that there were something on that projector too old (gate, sprockets) because the projs were 8 years old.

Now I'm working in a new multiplex with all new V5 and I'm facing again the same problem. Before this new job I was at a 16plex with V5 but with curved gate and the problem wasn't there.

So I suppose that the gate IS the problem. We clean them perfectly every day, the tension is at minimum setting.

WHAT can I do? I have serveral print damaged...

Please note that on some prints the scrath is almost on all the surface of the DD square, on others there is just a little scratch in the bottom (like first perforation in the picture) like there is something attempting to strach the print...

I appreciate your help...

Bye
Antonio

Posted by John Pytlak (Member # 331) on 06-28-2003, 08:14 AM:

"Intermittent" scratches outside the picture area like that are often caused in the gate, or by the intermittent shoe. In this case, look for a burr or rough spot in those areas on any surface that touches the emulsion side. It's unlikely that type of scratch happened anywhere the film is moving continuously.

Posted by Mark Gulbrandsen (Member # 72) on 06-28-2003, 10:23 AM:

Antonio,
The best cure is to tell your boss that you need a new Kinoton Head!!! [thumbsup]

Those WON"T scratch the film......
Mark

Posted by Gordon McLeod (Member # 33) on 06-28-2003, 12:13 PM:

It is odd that it appears leading out of each perf
After the first pass of the print is there a single mark only by one perf per frame?
If so check the roller on the intermitent pad If it is on every one then I would check the rail of the trap or the edge of the apperture plate carriage also spotlessly clean the machine as that type of damage will defintely leave a telltale depsoit behind
Also check the large roller leading down to the sould head for a flat spot

Also you may want to use a strobe light to see if a small loop is forming below the trap between it and the intermitent and that the film is beating the lower edge of the rail

never seen that mark before the Vic5's usually are a very robust and gentel projector.

Posted by Antonio Marcheselli (Member # 373) on 06-29-2003, 05:53 AM:

quote:
Also you may want to use a strobe light to see if a small loop is forming below the trap between it and the intermitent and that the film is beating the lower edge of the rail

Gordon, what do you mean?

Bye
Antonio

Posted by Richard Fowler (Member # 893) on 06-29-2003, 06:38 AM:

Since you have the forward / reverse machine which has probably originally set up for acetate film, it may be more unkind to the more thin estar / mylar stock. The intermittent pad roller and upper rollers above the gate can be the source of problems. A part of the gate which may not be touched while in forward operation maybe touching the film during reverse. the stobe light would help you to freeze the image of the sprockets and other areas to locate the damage while the machine is in motion.

Posted by Antonio Marcheselli (Member # 373) on 06-30-2003, 06:20 AM:

Richard,

I had two forward-reverse machine. Now I'm using normal V5.

Interesting thing the strobe light tecnique... I never seen/used it.

Bye
A

Posted by Larry Zuverink (Member # 1483) on 06-30-2003, 01:10 PM:

Antonio,
Cinemeccanica's are very rough on SRD. I don't know Italy's number but you can give Samuel Hynds a call in the US office at 626.939.0811. He is really good and has helped me find some strange problems.

Posted by Dave Macaulay (Member # 813) on 06-30-2003, 10:23 PM:

The strobe is a great tool for seeing what's really happening in the running projector. You need one with adjustable and stable flash speed. A "party" strobe will probably not be stable enough for this but worth a try. Once you synchronize the flashes to the frame rate, the machinery appears to be stationary. adjusting so the speed is slightly different makes the movement appear in slow motion, and you can see exactly what the film is doing (and hitting) as it gets jerked through. Just remember that everything is actually still turning! There is a great temptation to stick your finger in to feel something because it really looks like it's not moving.

Posted by Philippe Laude (Member # 79) on 07-01-2003, 03:45 AM:

Mark,
ANY poorly maintained projector will damage prints!

Philippe Laude

Posted by Antonio Marcheselli (Member # 373) on 07-01-2003, 04:53 AM:

Philippe

My projectors are nor poorly maintained!! [Wink]

Bye
A

Posted by John Pytlak (Member # 331) on 07-02-2003, 10:43 AM:

Strobes for motion analysis:

Reliability Direct

Electrical Contractor

Test Equipment and Tools

Homemade Strobe Mod

LED Strobe

Posted by Carl Martin (Member # 1146) on 08-05-2003, 01:58 PM:

just the other night i played a print with similar abrasions. it looked like every 3rd-5th data block was scratched (in the few places i stopped to check while winding, after noticing the problem). i didn't notice any sound problem until the last 2 reels, when there were some of those clicking block repeats mentioned in another thread. i could only play it once, or i would have verified in the booth that it wasn't actually dropping out.

carl