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Author Topic: Mysterious Sound Dropout Martin McCaffery Film God Posts: 2481 From: Montgomery, AL Registered: Jun 99 posted 10-05-2010 08:32 PM                        Dolby 650, Kelmar basement readers. Film has a damaged digital track, so reverted to SR About 10 mins into the film the sound looses most of the volume and most of the depth. Sounds like it is running through the Center horn only. All amps are lit and indicating on. The sound was bad in the monitor, so not a speaker problem. 650 meter shows all channels are working, and we are getting faint sound out of the LR on the monitor, though had to boost the volume to 9+. After about 10 mins, sound pops back on and all is well (so far). We've been running the print since Saturday and haven't had this problem. Any suggestions as to where to look for a cause, and possible tests to replicate it?  |  IP: Logged Geena Phillips Expert Film Handler Posts: 198 From: Norcross, GA / USA Registered: Apr 2006 posted 10-05-2010 09:15 PM                        What kind of damage does the film have? If it's sprocket damage, it's possible that the film was thrown slightly off the path. That could also explain why it's not happening every time.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 10-05-2010 09:27 PM                       I would guess the LED current is dropping from a bad power supply perhaps so your Dolby Level is no longer anywhere near correct. This would cause the Noise reduction to mistrack severely and explain the weird sound. I would run a loop before the show and set the level and again at the next opportunity after the show without switching off the reader LED. Just a guess though.  |  IP: Logged Martin McCaffery Film God Posts: 2481 From: Montgomery, AL Registered: Jun 99 posted 10-05-2010 10:06 PM                        Not sprocket damage, just scratching and worn Dolby track. Would the bad power supply just go out suddenly then come back on?  |  IP: Logged Marty Carr Film Handler Posts: 8 From: Greenfield, IN, USA Registered: May 2009 posted 10-05-2010 11:11 PM                     Earlier Kelmar power supplies have a problem of over heating at the plug connection. This will cause the problem your are having. i have changed out a lot of these boards over the years. Open up the power supply and you can see the darkness around the plug.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-06-2010 01:09 AM                     I have had that issue with all the kelmar supply's  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 10-06-2010 09:34 AM                     So have I. The soldering came undone where the connector is attached to the board.  |  IP: Logged Martin McCaffery Film God Posts: 2481 From: Montgomery, AL Registered: Jun 99 posted 10-06-2010 01:14 PM                        No visible signs of burning anywhere I can see without removing the unit. I'll keep an eye on it and see if it happens again.  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 10-06-2010 01:27 PM                     They didn't "look" burnt, but the soldered connection became intermittent and the levels were way off. Here's a blast from the past: Blast from the Past  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-06-2010 06:20 PM                        They are right. The power supply that goes intermittent supplies the preamp board on the basement reader. You won't know you have this problem if the digital is running. Likewisr both LEDs look OK. Louis  |  IP: Logged

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