Film-Tech Forum ARCHIVE: Staticy tapping sound

This is topic Staticy tapping sound in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Adam Hisle (Member # 1307) on 06-24-2002, 07:40 PM:

Im an employee of a theatre, and in some of our theatres we have a crackly static sound. Is this a film problem? Also answer me this, on one of our prints of yaya sisterhood there is intermittent loud bass noises like someone is stomping. Can this be cleaned? or is it part of emulsion? Thanks for your reply, Im a pretty big newbie at this film thing but i want to know as much as possible so i can be a film handler some day. (The one at my theatre is REALLY bad. 2 channel DTS, SDDS, pretty ugly.) Thanks!

Posted by Randy Stankey (Member # 64) on 06-24-2002, 09:14 PM:

Okay, without knowing what kind of projector you have I'm going to look into my crystal ball and say you should do one of two things:

1) Clean your film and the entire projector. Get all the dirt out of it and make sure all the nuts, blots and screws are in place and properly tightened.

2) Replace the drive belts on the back of the projector but make sure you clean out all the black junk built up in there. Again, make sure everything's tightened properly. Also check the alignment of the pulleys.

I'll explain more later...

Posted by Brad Miller (Member # 2) on 06-24-2002, 09:31 PM:

Hmmmmm, crackly static...Century projector with a motor that is not grounded? Rumble/thumps...I've seen this happen and forget what John Pytlak said it was, but it was a printing defect.

Posted by Josh Jones (Member # 447) on 06-24-2002, 10:23 PM:

The thumping would be caused by a print where the silver redeveloper was not distributed evenly during processing, leaving some parts of the soundtrack, "raw" or not properly developed. in a case like that, request a new print.

Josh

Posted by Gordon McLeod (Member # 33) on 06-24-2002, 10:34 PM:

Well it isn't the printing issue or dirt if it does it in digital mode
Most likely bad grounding or dirty mains power
Also the bypass relays on the processor can create that effect
If it was analogue system then it is probably reading the DTS timecode and the static is often static electricity dischargeing to the solar cell

Posted by John Pytlak (Member # 331) on 06-25-2002, 09:13 AM:

"Crackly static" can come from many sources. Was it only present when the film was running? Or was it there in the pre-show music or when there was no input to the sound system? Was it in all channels, or just one?

A "thumping" or "whooshing" sound with an analog soundtrack could be due to a soundtrack application (silver redevelopment) problem. A motorboating or "putt-putt-putt" sound could be due to misalignment of the analog sound reader, or sprocket runoff damage to the print.

Do the sound problems remain constant through the trailers and feature? If so, it it more likely the equipment/alignment than the film itself.

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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 Scott Manley (Member # 867) on 06-25-2002, 10:33 AM:

Years ago I had one house that would have a rumbling sound....I found that it had it even without film running....the fix I used back then was putting a "insulation" behind the cell mount.
So maybe see if the sound is present without film.

Posted by Randy Stankey (Member # 64) on 06-25-2002, 12:13 PM:

Yes, Scott! This is where I was going with solution #2.

When I was working on a problem that sounded similar to this I found that the drive belts (Simplex PR-1050+5 Star) had become worn out and they were transmitting vibration through to the cell.

Replacing the belts and cleaning out all the gunk solved the problem. Realigning the pulleys made sure it didn't happen again.

Posted by Scott Manley (Member # 867) on 06-25-2002, 02:31 PM:

AH HAH.......ok Randy...

Mine happened when I had been only working as a projectionist for about a year....so I just stopped after I added the thing behind the cell.

Posted by Randy Stankey (Member # 64) on 06-25-2002, 03:02 PM:

I'd say that's an admirable fix, even if only temporary. (Or "permanently temporary"

)

Another one that has bitten me in the ass a couple of times is worn out bearings on the impedance drum shaft. When this happens you'll get either a grinding noise like an old washing machine or a warble caused by uneven rotation of the drum. Again, replacing the worn/damaged parts and making sure the alignment of parts is correct will make sure it doesn't happen again.

The "trick" is getting somebody to believe you!
My boss (who was a corporate manager, not a technician) didn't believe me when I told him that this was a problem. I had to get him into the theatre and demonstrate it to him in person. The machine had been repaired so there was no extraneous sound coming though the system. When I took a screwdriver and tapped on one of the pulleys it made a ringing sound, clear as a bell. Even with the sound turned on but the projector turned off you could still hear it!

If your projector has the CCD/LED reader this will be a lot less of a problem. However if you still have a solar cell/exciter you will always have this problem to some degree. If you have a JaxLight in your projector you will get it REALLY bad! The preamp they make you install in the solar cell line has so much gain that it picks up every little vibration in the system. It's so bad that if your drive belts are frayed even a little bit you'll hear this little "Ping-ity Ping-Ping!" sound caused by the little frayed strands as they hit the flanges of the pulley as they fly by. It sounds like a mixture of static ("Frying eggs" sound) and a ringing sound.

I sat in front of that projector for 3 or 4 hours just staring at it as it ran trying to figure that one out! I had been there all damn night long since at least midnite. I didn't get it completely solved till about 7 or 8 in the morning.

Thus, the reason I said change your belts, clean out all the gunk and make sure your pulleys are perfectly aligned, lest the edges of the belts get frayed again in a short time.

Posted by Joseph D. Olson (Member # 1340) on 06-25-2002, 05:46 PM:

One of the things you failed to mention is whether this noise is coming through the sound system or from the projector head\platter\etc. If it's coming through the sound system for ya\ya sisterhood, before any actions are taken I would check to see if this is happening in the auditorium or just on the booth monitor. If it is happening on the sound system, is it happening in the trailers and tags too? Or is it always present no matter what print is running? If it were me, I would check all of these things before you try to convince any of the higher ups that there's a problem.

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So if old projectionists don't die, what happens when new projectionists get old?