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Author Topic: Trailers causing a BUZZ in Sound System Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 04-14-2005 04:06 AM                     Seem to be having a problem with a couple of trailers.They are causing a Buzz in the sound system but only in one auditorium.Most trailers and all features do not cause any problems on this screen. Move the trailers to another screen and the problem does not happen. Equipment: SH-7300 (first 5 star) sound head Component Engineering reader Ultra Stereo processor  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 04-14-2005 04:08 AM                     A-chain in the soundhead is off in the auditorium with the buzz. Have your tech realign it and you will be fine.  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 04-14-2005 06:36 AM                     Thanks Brad but why is it only a couple of trailers causing the Buzz and not everything we run on this machine? In fact I just ran the trailer and feature again and the buzz in the trailer was not there.It appears to be intermittent only on a couple of the trailers we are running.Haven't had the Buzz on any features we have run on this machine as I'm sure we would have got complaints.I am sure you are right about the A-chain as I can't get the full Dolby level. Would a quick fix be to run the offending trailer and if it does cause the Buzz to adjust the horizontal position of the lay-back roller on the sound drum until the Buzz dissappears?  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-14-2005 07:35 AM                        I'm betting that your A-chain is sufficiently bad that a slightly misprinted DTS timecode track is getting scanned and picked up by the solar cell. I suspect that you will find that the trailers that buzz have DTS tracks. If you have a white-light exciter, you could try replacing the bulb and try to set Dolby levels again. If the bulb is old, the filament might be sagging.  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 04-14-2005 07:59 AM                     Scott it is a Red light(Component Eng,) reader and I think you are right.I just need to maybe try a quick fix untill i can get a Tech to do a proper alignment. Actually it was "aligned" by a tech not that long ago. I only get techs passing my way on rare occassions.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 04-14-2005 09:47 AM                    if you have a buzz track loop run it and adjust your lateral in just slightly. Run dolby tone, if you have it, to check levels. If you don't have a buzz track use a piece of green band trailer that has nothing on the sound track audible. That way you can hear if you adjusted to much. You shouldn't have to adjust it very much. If possable use the green band from the trailer that is giving the problems. I have had to do this before as a temporary adjustment until our tech could get in to do the probper A-chain.  |  IP: Logged Dominic Espinosa Phenomenal Film Handler Posts: 1172 From: Boulder Creek, CA. Registered: Jan 2004 posted 04-14-2005 11:39 AM                     Agree with Daryl. I used the green band technique several times on an old R3 that had a faulty latteral guide and the owner was too cheap to fix it.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 04-14-2005 02:39 PM                     Course, we know that we hate the 5-star heads due to them using that solid flywheel instead of the dampened flywheel that the 4 star (SH-1000) had. We also notice when the machine is ramping up to speed, the scanner drum isn't catching up speed due to that solid flywheel. Thus, we see the film, as it leaves the middle constant speed sprocket loop forward due to the idler damper roller moving forward because of the turning resistance of the scanner drum with that solid flywheel. The film actually is travelling all over that scanner/lateral roller assembly until the flywheel catches up to speed. If the sound/dowser opens up while this film wander is happening, then that buzz can be apparent with the film not being completely settled over the scanner drum. I found out this the hard way with customers complaining of a buzz at the start of the show. I was having my threading leads way too early when dowser/sound opened and picking up the DTS track through the optical before the wander had settled. Course, this example above was just during startup. Ian's problem was with machine already fully running in which the answers to his problem from other members are valid suggestions. Wonder if Ian's problem is bearing related? Would he have bad scanner bearings causing the scanner drum shaft to not rotate smoothly? thx-Monte  |  IP: Logged Stephen Frazza Expert Film Handler Posts: 161 From: Nutley, NJ, USA Registered: Mar 2004 posted 04-14-2005 02:46 PM                        Just want to ask while we're on this subject - Dolby tone cat 69T should be run in mono,is that correct? Also should you run buzz track in format 03 stereo without surrounds or in 04 stereo with surrounds. Thanks  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-14-2005 02:58 PM                     69T should be run in mono (01) on all processors except the CP45 The Buzz track or cat 97 doesn't matter since one is looking at the signal on your scope on the preamp out point If a buzz track is being used by the "by the ear"method then mono is also fine since one wants no tones present idealy when listening on the monitor  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-14-2005 03:44 PM                        Special mention must be made: "first 5 star" These did not have the usual lateral guide assembly. Some had a "slider" instead. These were impossible to align (or install) Dolby in due to unusual mounts and extreme weave. (We did it anyway, however, at a theatre near D.C. in Georgetown.) In addition, now that we have to dance around the dts time code, I find that Buzz track is just not accurate enough. Try Dolby c/n 566 instead if you have access to an analyzer.  |  IP: Logged Joop de Gruiter Film Handler Posts: 33 From: Lund, Sweden Registered: Jul 99 posted 04-14-2005 04:29 PM                     Gordon, In the users manual for the cp45 it says to adjust dolby levels with the cp45 set to mono. Why should the cp45 differ from the cp55? I've been taught to do it in mono but if it works better in an other sound format i would like to know. On an Ultra Stereo i've been taught to do it set to stereo... Joop  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-14-2005 04:43 PM                     On some versions of the mother board mono summed the preamp output before the meters and the two trim pots will interact  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 04-15-2005 02:28 AM                     Thanks for the tips guys. Monte-the first thing I checked was the bearings and they feel fine. Louis was correct in saying we have the POS lateral guide assembly which does have way too much weave. The other thing that I have just learnt is to run the Dolby test loop in MONO-I've always done it in stereo. So am I correct in saying that a quick fix is to run the Buzz track in MONO and adjust the lateral guide until NO TONES are heard? Then do a Dolby level check-in MONO!! The other thing I don't understand is why the BUZZ is not apparent when I run a DTS feature on this machine!!  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 04-15-2005 02:58 AM                     quote: The other thing I don't understand is why the BUZZ is not apparent when I run a DTS feature on this machine!! ..when DTS is engaged, the processor have switched over to the digital information coming from the DTS player and not needing the optical pickup-if that helps any.... I had to service a theatre of our with the same sort of problem-buzz in the trailers, but when feature kicked in playing DTS, all was good. Turned out that a loose wire was apparent in the camera connections down in the optical section of the 5-star...that was an easy fix. So, maybe check line connections coming from your camera to the preamp section of the processor. Might have an open ground or something. Yes, buzz track and the dolby tone play in mono. Buzz track is where you don't want to hear anything. Dolby tone sets the output levels. -thx Monte  |  IP: Logged

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