my profile | my password | search | faq & rules | forum home

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

This topic comprises 2 pages: 1  2

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                        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?  |  IP: Logged Mike Babb Master Film Handler Posts: 250 From: Norwich UK Registered: Jul 2002 posted 08-09-2004 12:31 AM                        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.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 08-09-2004 12:46 AM                        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.  |  IP: Logged 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                        Did you see if it goes away with the xenon lamp shut off? It could be light 'from' the shutter.  |  IP: Logged Dominic Espinosa Phenomenal Film Handler Posts: 1172 From: Boulder Creek, CA. Registered: Jan 2004 posted 08-09-2004 02:26 AM                     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?  |  IP: Logged Stephen Jones Master Film Handler Posts: 314 From: Geelong Victoria Australia Registered: Jun 99 posted 08-09-2004 03:10 AM                     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  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 08-09-2004 08:51 AM                        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?  |  IP: Logged Mitchell Dvoskin Phenomenal Film Handler Posts: 1869 From: West Milford, NJ, USA Registered: Jan 2001 posted 08-09-2004 09:00 AM                     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  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 08-09-2004 09:03 AM                    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.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 08-09-2004 09:03 AM                        I already did that (business card) to establish whether it really is on both channels. Unfortunately it is!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 08-09-2004 11:41 AM                     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  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 08-09-2004 12:28 PM                     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.  |  IP: Logged Mike Babb Master Film Handler Posts: 250 From: Norwich UK Registered: Jul 2002 posted 08-09-2004 07:57 PM                        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.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 08-09-2004 10:16 PM                     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.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 08-10-2004 01:34 AM                     Check your preamp card out as well. Recently had one go bad and start oscillating at random.  |  IP: Logged

All times are Central (GMT -6:00)

This topic comprises 2 pages: 1  2

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.