Film-Tech Forum ARCHIVE: Question about scratches

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Posted by Jeremiah Teague (Member # 5052) on 03-11-2009, 06:31 PM:

I've posted before about some scratches I've been getting. The advise I got was to run test reels (trailers) through all the projectors 50 times to determine which Christi P35GPS' are scratching prints. I've found 2 that are. I can't find where the problem lies. Please let me know any ideas you have.

Projector #8 (with Dolby Digital Head):
(After 15 run throughs)

(After 30 run throughs)

It's a fairly straight line with a little wiggle. I can't find any protrusions on the projector.

Projector #16 (with DTS timecode reader head:
(After 25 run throughs)

The only thing I can think that would cause this would be having the film ride on top of the sprockets, but this isn't happening (I can't think of the film even running if this were happening). The green dots are very erratic and after more plays, the black cat scratches start to show up.

Posted by Ken Lackner (Member # 1002) on 03-11-2009, 06:45 PM:

I'm sure many others will chime in here with suggestions for both projectors, but one thing I can think of for #16 is your failsafe. If you have the type of failsafe that uses mechanical drop arms, and the film rides on top of bearings, those bearings can be a source of trouble. Although they should only touch the edges of the film outside the picture and soundtrack (except, of course, for the SDDS track), I have seen some where the edge of the bearing rides just inside the image area of the film. Xetron, Big Sky, and "Christie" (manufactured by Speco) failsafes use this type of design. I believe Kelmar does, too, but I'm not 100 percent on that one.

Please list your entire setup, as it will help greatly in troubleshooting. The problem very well may not be in the projector head.

Posted by Joe Redifer (Member # 3) on 03-11-2009, 06:53 PM:

Agreed. What kind of platters do you have? I get the green dots on the right side occasionally, but not that severe. I have Strong platters. I have FPS-350 failsafes which do not have the mechanical drop arms.

If the problem were in the projector, the black scratches would probably not move much. HOWEVER I did troubleshoot a theater once that had an old Simplex soundhead and it had two sprockets in it due it its pre-19th century design. It has a small "loop" between these two sprockets and the film would come off the first sprocket when exiting it and lightly rub against the keeper/pad roller, causing light scratches over time that weren't perfectly still.

Posted by Brad Miller (Member # 2) on 03-11-2009, 09:34 PM:

You don't have slap guards on the bottom side of your ultramittent and you are making your lower loops way too big. Seen it a million times.

Posted by Monte L Fullmer (Member # 2797) on 03-11-2009, 11:06 PM:

When I ran Christies, I had an operator that would make his bottom loop too big and the loop would slap on the holding screw for the stripper. Thus, that slapping would leave a peck mark dead lower center of each frame.

I got after him to make the loops the correct way - the way the Christie theading chart would show.

Squiggly lines though - isn't that a platter problem since it's more of a continual thing than the side peck marks?

Posted by Jeremiah Teague (Member # 5052) on 03-11-2009, 11:56 PM:

The fail safe is a Component Engineering FM-35. I don't think this is the type of fail safe your talking about, Ken. I may be wrong, though.

The platters are chrisie aw3r. I haven't noticed anything wrong with them (film isn't rubbing on the platters or bouncing) but I've never been trained on searching for this type of thing.

We do have the slap guards and I've been threading properly since that last topic posted Last Topic . And since these scratches are only happening on 2 projectors, I'm hesitant to say it's human error.

I'll take some pictures of the equipment if you think that will help. I really just want to stop damaging prints. It's annoying as hell and I hate not knowing why.

Posted by Ken Lackner (Member # 1002) on 03-12-2009, 05:21 AM:

You are correct; the FM-35 uses a proximity sensor, not the mechanical drop arms I described.

Posted by Monte L Fullmer (Member # 2797) on 03-12-2009, 11:59 AM:

These squiggly lines - on the base or emulsion side of the print?

Posted by Brian Guckian (Member # 1678) on 03-13-2009, 04:29 PM:

Also, check the brains in the platters concerned. Make sure there's nothing touching the image area of the film there.

Check every single roller from the platter through to the projector for proper rotation, including the rollers in the brain and on the FM-35.

Posted by Jeremiah Teague (Member # 5052) on 03-15-2009, 09:59 PM:

The scratches on #8 appear to be on the base of the film. They are very difficult to see on the film itself.

I've already checked all the rollers and the brain. We keep them lubed and cleaned.

Posted by Gordon Ford (Member # 1980) on 03-16-2009, 04:17 PM:

Ok lets look at average film path, now where does the film actually weave like that? not usually on rollers, but in between rollers maybe.
So lok at the film path when lacing up and see if anything is close to film when laced up, anything very close to film plane?
Look at feed off unit, does film "relax" or drop when not under tension when running?
gate area is unlikely as film is under tension and would be stable running, unless you have excessive wear somewhere , but that is likely to show on screen.
Without expert knowledge of the equipment you are using, the best advice is lace up a small a trailer and LOOK at all ther film path where weave could occur.
The scratches are black so that will be on the base, the emulsion scratches are white or coloured, depending how deep they go and which colour layers are removed.
As to the green dots, the most likely cause is on a constant speed sprocket, either has been laced incorrectly, also if this is the case you will find that the scratches could be caused by the one side teeth of the constant speed sprocket,( this would probably be on the emulsion side) therefore being done at the same time as the wavy scratches? or has poor quality machining inside the teeth leaving slightly raised edges, is there a new sprocket?
Best of luck in your investigations sherlock LOL
Regards
Gordon

Posted by John Wilson (Member # 269) on 03-16-2009, 04:34 PM:

Gordon,

You registered in October 2003 yet the above is your first post? [eyes]

What took you so long? It's not that frightening here is it? [evil]

Welcome to another 'active' member. [thumbsup]

Posted by Brad Miller (Member # 2) on 03-16-2009, 08:45 PM:

Quick question, do the curves in the scratches roll up and down, or is the "curve" of it stationary as far as vertical? (Or are the scratches just all completely random and curved?)

Posted by Jeremiah Teague (Member # 5052) on 03-17-2009, 02:45 AM:

We just recently moved/swapped the digital projector in #9 with the p35 at #8. They did a lousy job setting up the platter tree and the black rollers above and below the head. Another guy and I reset the black rollers (not sure what they're called. they carry the film from platter to head and vice versa) and connecting platter tree rollers. We have not gotten any scratches so far. I don't want to get too excited yet but that top black roller has the base of the film riding on it and if it was rotated wrong, I could see this causing the scratch. I hope this is the issue, but I'm frustrated because that's something I check everytime I hit start. Perhaps some projectors/prints are more liberal in what is acceptable before scratches occur?

Brad, the black scratches are essentially lots of cat scratches that form into a uniform line swiveling to the left and right, randomly, in very small amounts. There isn't that much movement, but it is very noticable. I'm sorry, but I'm not sure what you mean by "roll up and down". I hope the above was the answer.

I'll keep everyone posted. I'm doing presentation checks all week.

For the dots on #16, I've made a loop and I've played it for 10 minutes (which would be about 120 run-throughs if it were a movie). I didn't get any dots on the loop at all. Unfortunatly the film doesn't lay on the bottom and top constant-speed sprokets like it does when running a film. I'm going to figure that out tomorrow.

Thanks again for all the help. You guys rock!

Posted by Gordon Ford (Member # 1980) on 03-17-2009, 07:54 PM:

Hi John,
Thanks for the welcome, only been a projectionist since 1962, so not as knowledgeable about some equipment as most on here.
Have run:
Philips DP 70
Philips DP75
Philips/Kinoton Fp20
Kinoton st200/270 cakestands
Ross GC3
BTH supa
Mainly UK projectors.
Have dabbled with Cinemechanica Not a lot.
Regards
Gordon

Posted by Jeremiah Teague (Member # 5052) on 04-07-2009, 12:34 AM:

That upper black roller was, indeed, the case of the black vertical scratches on #8.

I tried running test loops on #16 and couldn't replicate the green dots. I'm still convinced that it's caused by a sproket roller, though. The test loops aren't pulled tight on the top and bottom constant-speed sproket rollers. I can't figure out how to do that.

Let me know if you have any ideas. Or tell me if you think I'm wrong about what's causing those erratic green dots.

Posted by Andrew Bangs (Member # 4938) on 04-07-2009, 11:37 AM:

I have been having a similar problem with green dots but I think mine are due to booth monkeys not threading properly and they get the film on the edge of a roller in the fail safe at the bottom of our projector. No I am not sure if you have the same fail safe or if their could be another roller that the film is "jumping the curb" as i say to my booth monkeys. just look for anything suspicious like that and have them check the film path as during the movie as well as when they thread it. Ours actually started jumping up sometimes when it hit a splice. How??? I have no idea but that seemed to be what was happening.