This is topic Thin, Densely Packed, Horizontal Scratches in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Chris Rasmussen (Member # 3015) on 06-28-2008, 02:38 AM:
 
I’m trying to determine the cause of base-side, horizontal scratches, running from beginning to end of two prints in a tri-plex.

The scratches are razor thin, irregular and densely packed – around ten to fifteen per four-perf frame – and run fully across the surface, past the sprocket holes and out to the edges. The scratches vary, some not fully stretching across the film’s width, but with no regularity; some scratches run from the soundtrack side inwards, some from the other and some just in the center. There is no discernable pattern. The scratches are consistently random, with a full gamut appearing several times per frame.

The equipment in both houses wherein this may have originated: Century heads (one JJ and one SA) and TR4 soundheads upgraded with red LEDs. Both have Component Engineering automation/failsafes. The platters are AW3 with newer style green rollers, and both platters are within five feet of the projectors.

The film transport paths have been thoroughly inspected: all rollers are properly aligned and turn freely. Pad rollers turn freely, have correct tension and proper alignment. Film gate tension and alignment are likewise correct. AW3 platter return arms have proper tension and all platters are properly timed. The slide bar orientation pins are all correctly aligned and the roller cluster rest plates haven’t been deformed, so the clusters sit at the correct levels to feed film onto the platters without incurring scratches.

The circumstances: the opening projectionist noticed the scratches on one print at startup of the first matinee show on Thursday. I was there, inspected the film feeding from the platter and noted that the scratches had occurred previously. As it turns out, the prints in two sides, both of which had played scratch-free for several days, seemed to have been damaged on Wednesday evening. Unfortunately, a print swap between the two booths leaves me unable to determine in which booth the problem struck.

The conundrum: there is no obvious physical cause for the scratches. There are no accompanying vertical scratches. The scratches are perfectly horizontal, not diagonal, like platter-feeding scratches from improperly set roller-cluster height. The prints do not seem to wind overly tightly on platters in either booth, which I mention because it’s been suggested that excessive take-up platter tension combined with a hesitant roller might cause the scratches. I don’t believe this is the case because the current return arm springs that control the tension have been in place for over a year and are unlikely to get tighter with age.

Has anyone out there seen or heard of a case of perfectly horizontal scratches as I’ve described? I must admit I’m at wits end trying to come up with a plausible cause. I'm a full-time field tech with too many years experience to be thrown by some wimpy little scratches... or so I thought!

With hope and appreciation ~

Chris
 

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Posted by Brad Miller (Member # 2) on 06-28-2008, 02:44 AM:
 
I would have to blame this on piracy. Clearly some bootlegger broke into your building after hours, stole the print, transferred it to video (scratching it in the process), then put it back before you opened the next day.

If for some oddball chance that actually didn't happen, pictures of the scratches as well as your equipment setup would help get feedback. Even though you gave a great description, I can't think of anything offhand.
 

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Posted by Chris Rasmussen (Member # 3015) on 06-28-2008, 03:48 AM:
 
Thanks Brad,

Methinks you may be onto something! Gremlins, while the usual suspects in such cases, have vehemently denied any involvement, so overnight break-in film pirates are likely the only clearly plausible culprits. (Color me in awe of your powers of insight; your Kung Fu is truly more powerful than mine...)

Humbly,

Chris ~

PS - I'll try shooting some good close up pics so you can see the pirate's fingerprints.
 

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Posted by Michael Cunningham (Member # 210) on 06-28-2008, 06:23 AM:
 
So they were fine for a while and then horribly scratched in one night? Has the damage gotten any worse since? If not, that's got to be threading error. Not being too familiar with those heads, could this be due to an oversized loop slapping against something? That's the one thing that comes to mind for horizontal scratching.
 

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Posted by Louis Bornwasser (Member # 3063) on 06-28-2008, 07:09 AM:
 
Base side scratches (on a Century) are almost always related to the sound drum. It is the only thing that touches the base side. I would suggest that an occasionally loose threading of the dancer assembly would look just this way. (Also true of Dolby penthouses.)

Easy enough to hold the "damage" up to the drum. Notice the drum does not cover the entire width of the film? Is the damage full-width? Or does it stop to agree with the touching area of the drum? Louis
 

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Posted by Randy Stankey (Member # 64) on 06-28-2008, 07:57 AM:
 
Did somebody make the loops too big so that the film slaps against the projector bulkhead or some other stationary part?

Just guessing...
 

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Posted by Darryl Spicer (Member # 711) on 06-28-2008, 12:31 PM:
 

quote: Chris Rasmussen

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I’m trying to determine the cause of base-side, horizontal scratches, running from beginning to end of two prints in a tri-plex.

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quote: Darryl Spicer

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Sound drum normaly causes vertical base side scratches

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..unless the film was wound too tight around the drum due to the lateral guide rollers of someone not knowing the "line and arrow" marking on the roller arms...which I've seen TONS of operations having the film so tight across the scanner drum on both soundhead and Dolby readers...and with "pressing" in horizontal scratches on the base side of the film.

And I've seen the same with platter rollers on the rewind side of the transports-anything when film is under tension.
 

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Posted by Carl Martin (Member # 1146) on 06-29-2008, 02:42 AM:
 
my girlfriend's iphone was not up to the task of documenting this scratching. none of the screenshots came out, and this was the clearest shot of the film itself:



i was able to duplicate the scratching by taking up on the bottom platter with the roller cluster at the lowest (unintended) position, as described above. the scratches do in fact stay horizontal (bowed just slightly downward) over the course of a normal-length movie. so that about solves that.

thanks!
 

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Posted by Chris Rasmussen (Member # 3015) on 06-29-2008, 03:08 AM:
 
Many thanks to all for supplying good theories and to Carl for his extensive testing and confirmation that the culprit was indeed pilot error rather than the suspected film pirates or Gremlins.

Cheers!

Chris ~
 

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Posted by Brad Miller (Member # 2) on 06-29-2008, 06:24 AM:
 
Sounds like you have the old style AW3 takeup slidebars. You can either buy a new one (the new ones have a really long bottom set pin so it is impossible to set the roller cluster too far down), or you can wrap some gaffer's tape around the bottom part of the slidebar such that the roller cluster can't be set lower than the bottom deck's set pin.
 

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Posted by Bruce McGee (Member # 131) on 06-29-2008, 10:36 PM:
 
Wow. I have trouble getting my people to even USE the bottom platters on our AW3's!

Glad you found out the cause of the scratching.
 

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Posted by John Wilson (Member # 269) on 06-29-2008, 11:01 PM:
 
I was taking up on the bottom plate (as I like to do) and the operator who was taking over from me said: "Why are you using the spare plate?"


 

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