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Author Topic: CP650 sound "wow" on changeovers running Dolby Digital... Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-23-2011 02:35 PM                     Have a strange problem with the CP650 in UC Irvine's HIB 100 screening room.....has anyone else had this happen? During changeovers, after the incoming projector is started, but before the actual changeover, the sound playing on the outgoing projector goes nuts, acting as if the projector suddenly slowed down and is re-accelerating. It happens going in both directions, i.e. from 1-2 and 2-1. This came on suddenly and after the processor wigged out during a show (it switched itself from Format 10 to 04). My thought is the CAT 773 may be bad.....my thought is that the card is mistakenly clocking the digital data to the incoming machine too early while the outgoing machine is still playing. Yes, I have the proper changeover and motor start commands connected and they are working. At first I thought it was a projector problem as my #2 machine would on occasion hang start at half speed, but it is happening while the machines are running normally, and I never had trouble with the #1 machine. Any thoughts?  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 10-23-2011 06:50 PM                     scanner drums hanging up to pick up speed, since SR-D will 'wow' if data speed isn't correct? There is a little 4plex in this area that has the BACP penthouse reader sitting on top of an XL/5Star setup, but the motor is an induction motor that will run at slightly odd speeds if the electricity demand is high..and they, on occasion, have these 'wow' sounds in digital. I mentioned to them, to cure this, is to get a sync motor on there to eliminate this 'wow' .... oh well, that was 4yrs ago..and they haven't done anything about it yet.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-23-2011 07:02 PM                     Good point Monte, but it is happening on the projector that is still running the last 8 seconds of the reel, not the incoming machine. And it is happening ONLY during the runup time of the incoming machine.... And these are on new BACP DSTR-20 penthouses.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 10-23-2011 07:21 PM                     ..maybe, a small arguement between the two units then, esp when No.2 starts to roll and senses data and does something to cause the arguement..? What would happen if data wasn't sensed by No.2 (like using a blank leader) until changeover?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-24-2011 05:27 PM                     Yeah I agree some sort of conflict is happening in both directions...and I don't know yet what the effect of a blank leader would be yet..probably no change as I had the problem with my Dolby Digital trailers and they are all built on one reel with true blank leaders between. Testing time is a problem now as the room is in use a lot for classes so I may not be able to test it out for a while. I might try swapping the 773 card from the other screening room's processor to see if that solves it. Sam Chavez, what is your thought on all of this?  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 10-24-2011 10:25 PM                     Does the problem sound the same when changing from projector #1 to projector #2 as it sounds when changing from #2 to #1? What if one projector is running at a constant speed but slightly slower or faster than the other? Would the digital processor ramp the sound up or ramp it down in order to blend the incoming and outgoing tracks together? If so, would you hear an increasing pitch when changing over in one direction and a decreasing pitch when changing over in the other direction? Thus, if true, a speed check between projectors might be in order. Also compare the ramp-up time between both projectors. Otherwise, check the impedance drums for drag or slippage. Mostly just spitballing, here but that's all I can think of.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 10-24-2011 10:50 PM                    Wow - this sounds sort of familiar. Good luck.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-25-2011 12:23 AM                     Mark: Thank you for posting that link. I read thru that thread and the problem isn't quite the same...splices aren't in play in this case and I am not running a platter..but there was a lot of great info found there. quote: Randy Stankey Does the problem sound the same when changing from projector #1 to projector #2 as it sounds when changing from #2 to #1? What if one projector is running at a constant speed but slightly slower or faster than the other? Would the digital processor ramp the sound up or ramp it down in order to blend the incoming and outgoing tracks together? If so, would you hear an increasing pitch when changing over in one direction and a decreasing pitch when changing over in the other direction? To answer your questions: Yes it is the same effect going from 1 to 2 and 2 to 1... Both machines are running within 1/10 of a frame of each other (look at the pics I posted in the warehouse and you'll see the rate display.) The problem happens because the incoming machine ramps up to speed (inverter drives) and it ONLY happens when the incoming machine is started. As in my first post, it seems like the processor is clocking to the incoming machine as soon as the motor starts and is not "waiting" for the actual changeover to take place before clocking to the incoming track. (Footnote: I work on several other screening rooms with CP-650s and two projectors, many of which also have inverters with the same ramp-up times and they do NOT have this issue.) My understanding is that in the changeover environment (with the presence of the second Motor Start command,) it should not be blending the transitions at all. The pitch change is an abrupt drop in pitch which ramps back up (at the same rate as the incoming projector's speed) just before the actual changeover. And it happens the same in both directions of reel change. So it appears to be some sort of processor problem.... Or, it could be the ghost of the original installer f**king with me...the #2 half-speed start issue I reported about earlier started right after he died. And the half-speed start has been fixed....so that's not it. Again, to be clear, here's the scenario: Playing the end of reel #1, as soon as the projector for reel #2 is started, the sound playing ON REEL 1, slows in pitch then ramps back up matching the ramp up speed of reel #2 even BEFORE the actual changeover. This happens on ALL reel changes regardless of which machine is the running or incoming one.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-25-2011 07:11 AM                       Tony, Did it always do this and it has just been noticed? Just a wild shot here, but what if the video cables are interchanged? Also, maybe the motor relay wires are transposed but this should be more obvious. Sounds to me like the incoming projector is making a changeover early but since you have a blank leader on the incoming projector it hangs onto to the outgoing audio in the buffer until it sees valid audio on the incoming projector. Norm Cerda at Dolby is very good on this sort of issue.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-25-2011 01:34 PM                     Hi Sam, how's ShoEast? It has just started doing this, it was working fine before, it even ran a test print I have after installation with no issues. The issue is there with standard leaders or with blank leaders. Like I mentioned in my first post, there was an incident a while ago during a screening where, in mid-reel, the processor freaked out (popping noises in the sound) and switched itself from Format 10 to Format 04....very odd. This current problem appeared shortly after. IIRC I ran a screening or two in SR before this latest digital screening but after the freakout and had noticed no issues in analog. I will triple-check the motor start and changeover relays and signals to the processor, but I am pretty sure they are still working ok. I also need to get back and look through the event log to see if that freakout showed up. Is Norm at Dolby LA or San Fran?  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-25-2011 04:18 PM                       Norm is in SF at tech services. 415 645 5205.  |  IP: Logged Kris Verhanneman Expert Film Handler Posts: 182 From: Belgium Registered: Dec 2009 posted 10-26-2011 08:27 AM                     Any way of trying/swaping at the location with another working CP?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-26-2011 01:14 PM                     Thanks Sam. Kris, yeah that is one option I have as the two screening rooms there are CP-650 equipped. I can't leave them swapped though as the University has them asset tagged to each room, and they get touchy about moving things around. I will not be able to do any testing until I get the room scheduled for maintenance time which is another difficult thing there of late.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 10-26-2011 08:42 PM                    Just curious... You're saying that it does this with a blank leader in the incoming projector, meaning no SRD track at all? What happens if you block the exciter's light on the incoming projector's penthouse reader while the projector ramps up to speed? In essence blocking the Dolby processor from "seeing" the film start up at all. Thread the leader through the reader like normal, but block the light from getting to the camera. Stick an index card in front of it or something when your motor is ramping up.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 10-27-2011 12:32 AM                     Well, got a chance to talk to Norm at Dolby today..he feels I'm on the right track with the CAT 773 being bad....or possibly the CAT 774 (control board). As I had suspected, he's never heard of this particular problem, but there have been a few rare issues with the CAT 773's before. (And he's heard of/read the other thread.) I was granted a 4-hour block of time this Saturday to work on it. Hopefully my other room will be down also so I can try swapping the 773 board to see if it fixes the problem. Mark: Good idea, and I have an easier way, I have power switches on the LED's for the penthouses so I can just kill the LED to see if it helps. I will post back on Sunday or Monday with the outcome.  |  IP: Logged

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