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TOPIC: Sound warble

Sound warble 19 Nov 2004 01:33 #22001

  • BurneyFalls
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My analog began sounding like crap a few days ago. DTS is fine. I noticed it when the trailer ROBOTS played and it wasn't on the dts trailer disk I was using.

I have an Component Engineering ASR-40, that is about six months old. If I got a manual or trouble-shooting guide with it, it got destroyed in the fire. Is there any routine maintenance that is supposed to be done to these? Do the heads require cleaning?

I think I liked my old exciter lamp better.
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Re: Sound warble 19 Nov 2004 10:17 #22002

  • Ken Layton
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Sound warble is usually caused by bad sound drum shaft bearings, worn sound drum shaft, or both. The ASR-40 has no moving parts, but if you want the manual you can get it at www.componentengineering.com and www.film-tech.com

You didn't mention the make/model of soundhead.

Don't forget to do a buzz track & Dolby tone adjustment too.

[This message has been edited by Ken Layton (edited November 19, 2004).]
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Re: Sound warble 19 Nov 2004 14:41 #22003

  • John Pytlak
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Watch the sound drum after the film runs out through the projector. Its inertia (large flywheel) should allow it to continue to rotate for many seconds after the film runs out. Rotate it by hand and see if there is any sticking. Be sure you are threading the film over the sound drum with the correct tension.

"Warble" is sometimes called "Wow and Flutter", and is especially noticeable in sustained musical notes, especially piano or violin. It is caused by minute variations in the film speed as it travels through the sound reader. Warble would not be related to "white light" or red LED reader differences.

John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
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Website: http://www.kodak.com/go/motion
John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Fax: +1 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion
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Re: Sound warble 20 Nov 2004 01:49 #22004

  • BurneyFalls
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It's an RCA 9030. We changed out the bearings today and that didn't fix it. My projectionist did discover that the film is loose when it passes the sound drum. He is going to change the spring tomorrow and see if that fixes the problem.
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Re: Sound warble 20 Nov 2004 02:55 #22005

  • rodeojack
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The film is supposed to have slack when threading that soundhead. It should have about 2 sprockets worth of slack after closing the lateral guide. If you pull it tight, it will sound awful.

It would be helpful if you'd describe exactly what "sounds like crap" means.
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Re: Sound warble 20 Nov 2004 09:37 #22006

  • Ken Layton
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Could the nut and tension spring on the back of the flywheel have come loose/fallen off?

Also check the lateral guide roller assembly for dirt/wear/flat spots/binding. Jack's right about the threading of this soundhead. It needs two sprocket hole slack when threading.
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Re: Sound warble 20 Nov 2004 12:16 #22007

  • BurneyFalls
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Thanks for the responses guys. We do leave the proper amount of slack in that loop. The sound is a definite warble. We will check the nut and tension spring on the back of the flywheel and the lateral guide roller assembly today.
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Re: Sound warble 20 Nov 2004 13:36 #22008

  • outaframe
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The sound drum is essentially a flywheel which serves to keep the film running through the light beam at constant speed and smoothly, so anything which interferes with that can cause your warble... Ken's suggestion to check the lateral guide roller for problems seems the most likely spot to suspect... Even minor flat spotting will make the film jumpy...
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Re: Sound warble 21 Nov 2004 01:56 #22009

  • BurneyFalls
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It was the tension spring and it is fixed. Thank you everyone.
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Re: Sound warble 21 Nov 2004 13:19 #22010

  • Mike
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2 days from problem to solution. That was beautiful!

Michael Hurley
Impresario
Michael Hurley
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Re: Sound warble 22 Nov 2004 20:17 #22011

One other issue with older simplex and RCA soundhead that luckily wasn't the issue here
but worth noting
they have a flywheel that is actually a flywheel inside a shell that has a viscus oil solution that couples the two togather and then to the shaft
If they get dinted then mechanical coupling occurs and then they can just go in the dumpster also if any foreign dirt or grit gets in them since there is onlya few thousanths of an inch clearnace between the outer casing and the actual drum will cause flutter as well
treat them with lots of respect
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