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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » Puzzling buzzing on 5Star (Page 1)

 
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Author Topic: Puzzling buzzing on 5Star
Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002


 - posted 08-08-2004 11:42 PM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
I have 2 5Star soundheads which produce a low, regular buzzing. It is not electrical (it speeds up and slows down when you switch the motor on and off), and not the perforation or DTS timecode either. I buzztracked and checked the L/R-alignment, and it is on both channels equally anyway. It does not come from the exciter, it is running on DC, and the other other soundhead is equipped with a red LED. I thought about the sound drum bearings or the friction roller coating, but in my experience, wear on these parts makes itself noticed in wowing rather than this low buzzing.
What am I missing here?

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Mike Babb
Expert Film Handler

Posts: 227
From: Norwich UK
Registered: Jul 2002


 - posted 08-09-2004 12:31 AM      Profile for Mike Babb   Author's Homepage   Email Mike Babb   Send New Private Message       Edit/Delete Post 
Can you see it at 100hz or so on your analyzer? I had this and it came from stray light hitting the sprockets and landing on the cell, or at least that's the theory.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002


 - posted 08-09-2004 12:46 AM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
There is no real peak, but it seems to be lower than 100Hz. The buzz covers the audio spectrum broadly up to a little higher than 100Hz. It didn't occur to me when I was a the location to hold the analyzer in front of the monitor to see if I could pick up the frequency I heard most prominently.

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Daryl C. W. O'Shea
Film God

Posts: 3977
From: Midland Ontario Canada (where Panavision & IMAX lenses come from)
Registered: Jun 2002


 - posted 08-09-2004 02:23 AM      Profile for Daryl C. W. O'Shea   Author's Homepage   Email Daryl C. W. O'Shea   Send New Private Message       Edit/Delete Post 
Did you see if it goes away with the xenon lamp shut off? It could be light 'from' the shutter.

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Dominic Espinosa
Phenomenal Film Handler

Posts: 1172
From: Boulder Creek, CA.
Registered: Jan 2004


 - posted 08-09-2004 02:26 AM      Profile for Dominic Espinosa   Email Dominic Espinosa   Send New Private Message       Edit/Delete Post 
If it speeds up and slows down with the motor could it be possible that you're getting some kind of interference from the opperation of the motor itself? Perhaps a loose connection or a wire that comes very close to the motor?

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Stephen Jones
Master Film Handler

Posts: 314
From: Geelong Victoria Australia
Registered: Jun 99


 - posted 08-09-2004 03:10 AM      Profile for Stephen Jones   Email Stephen Jones   Send New Private Message       Edit/Delete Post 
I tend to agree with Dominic on this as the same thing happened to me with a Bauer U3 found that the lead from the cell was rubbing against the stabaliser.This occcured after a service as it wasnt present before.Checked connections found was loose,moved lead from where it was touching retightened and all was well.

Steve

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002


 - posted 08-09-2004 08:51 AM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
No, the xenon lamp was off when I tested it. But it is a good thought. I will remember that when I come across a mystery problem that only occurs when the movie is playing, but not when I am testing it.
I will check the wiring. Though it does sound like something that enters the system by being read by the cell, because it somehow sounds "mechanic" (tak-tak-tak) rather than "electric" (bzzzz). It's not a sine wave, but a rapid buzzy pulse. Is that what your problem sounded like?

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Mitchell Dvoskin
Phenomenal Film Handler

Posts: 1813
From: West Milford, NJ, USA
Registered: Jan 2001


 - posted 08-09-2004 09:00 AM      Profile for Mitchell Dvoskin   Email Mitchell Dvoskin   Send New Private Message       Edit/Delete Post 
Take a business card or a small piece of paper and block all light to the cell while the film is running. If the buzz goes away, you know it is in some way a light problem (alignment or stray reflective light). If the buzz does not go away, you know it is an electrical problem.

/Mitchell

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Darryl Spicer
Film God

Posts: 3250
From: Lexington, KY, USA
Registered: Dec 2000


 - posted 08-09-2004 09:03 AM      Profile for Darryl Spicer     Send New Private Message       Edit/Delete Post 
check two things. One is do the belts have cracks in them. Secondly has the solar cell wireing come into contact with the belt drive causing the belt to rub up against it. I have had this happen do to the wire coming loose from a plastic wire clamp that is screwed into the frame allowing the wire to make contact with the belt and rubbing off the insulation.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002


 - posted 08-09-2004 09:03 AM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
I already did that (business card) to establish whether it really is on both channels. Unfortunately it is!

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Gordon McLeod
Film God

Posts: 9431
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 08-09-2004 11:41 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Connect a scope to the preamp and look at the shape of the wave form
Is it there with the motor not running?
It is possible that it is microphonics of bearing noise on the sprocket shaft bearings

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Brad Miller
Administrator

Posts: 17638
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 08-09-2004 12:28 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Just turn the motor on without film in the soundhead (with exciter/led on) and listen while you turn it off and it coasts to a stop. That will let you know if it's a grounding issue with the motor or other mechanical issues. You can knock 50% of it out right there in 30 seconds.

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Mike Babb
Expert Film Handler

Posts: 227
From: Norwich UK
Registered: Jul 2002


 - posted 08-09-2004 07:57 PM      Profile for Mike Babb   Author's Homepage   Email Mike Babb   Send New Private Message       Edit/Delete Post 
That 100Hz thing is something I'd probably check with pink noise, or maybe Dolby tone on an analyzer. I don't know if you are seeing the problem I ran into but it seemed to be the stray light picking up the edge of the sprocket holes, 4 x 24 puts it right about there. I "solved" mine once with a new LED (SH1000)and once with taking a thin cardboard spacer/gasket out (RCA), but in both cases I think the LED was not lined up properly with the film. When at Dolby school I was talking it over with Dustin and that was the theory, he had also seen something exactly like that.

I have also heard the "machine noise" being amplified through a Kelmar reverse scan, on a particularly loud Christie. This one you can hear by putting the processor in film format, turning on the motor (without film) and listening on the monitor or in the house. You can see it on the scope too.

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Randy Stankey
Film God

Posts: 6392
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 08-09-2004 10:16 PM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
I vote for microphonics.

I once sat in front of a projector (Simplex 5 Star) for HOURS just watching it run and listening to the noise and trying to figure out what the cause was.

I finally found out that the drive belts were cracked and frayed. The little pieces of frayed belt were "flinging" themselves against the sides of the pulley sheaves and causing the noise.

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Tony Bandiera Jr
Film God

Posts: 2931
From: Moreland Idaho
Registered: Apr 2004


 - posted 08-10-2004 01:34 AM      Profile for Tony Bandiera Jr   Email Tony Bandiera Jr   Send New Private Message       Edit/Delete Post 
Check your preamp card out as well. Recently had one go bad and start oscillating at random.

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