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Author Topic: Jax Lite cracking sound. Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 01-25-2010 09:42 PM                        I probably know the answer to this question, but I just want to bounce it off you guys to see if I'm right. Booth: (2) RCA 9050 sound heads with Super Simplex and ORC 1000 lamps. CP45 with Jax Lite and kneisley exciter supply. Right machine is fine. Sound is good (for a jaxlite), decodes fine, no hum, pops or cracking noise. Left machine... has a popping/snapping noise, seems to be mostly in the left speaker (bleeding over into center), right channel has it, but faint. Very little buzz, not noticable in playback. Noise is only there when film is playing. If machine is on (lamp, motor, etc.) but has NO FILM in it, there is no popping/snapping sound. Only when film is present. I think it's static build up from the running of the film in the projector (especially since its winter and dry) and its discarging on the cell and is being picked up in the cell. I just don't know how to isolate it. The wiring is set up as normal except the sheild is not hooked up at either end (projector or processor). When it is, I do get a buzz in the sound. If I try, grounding the cell to the casting, nothing seems to happen. The manual says that you can tap off of one of the LED power leads to the casting but only if there is a buzz or hum. That is not the problem. I did swap the projector inputs and its present on both Projector 1 and 2 inputs, so its definitely from the cell wiring back to the projector. Any suggestions? Thanks Bernie  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 01-25-2010 09:51 PM                     Sounds like left machine needs an "A" chain alignment .. optics picking up a bit of the edge of the DTS timecode track if the noise is left/center.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-25-2010 10:01 PM                     It is static probably the sounddrum bearings I usually add a piece of copper wire hammered flat on the top surface above cell and ground to the soundhead  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 01-25-2010 10:01 PM                        On a 1050, the sub frame is insulated on rubber standoffs. Be sure grounding cable connects the sub frame to the case of the soundhead. A good place to start. Louis  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 01-25-2010 10:50 PM                    You may have tried this but run the the reel on the good projector and make sure the soundtrack is not scratched. Change any belts that are being used. DTS soundtrack being read will make a high pitched blurrr sound or at least that is the sound I heard when this happens. Make sure all solar cell wiring connections are tight.  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 01-25-2010 10:56 PM                        Its not the DTS track (print I ran was pre DTS LLP 1993 stock). I know what that sounds like. This is more electrical interference instead of optical. Gordon: do you have a picture of how you mount the wire? I get the concept, the static is discharged through the wire instead of the cell. How close to the tip of the cell should the wire be? What gauge wire? I'm assuming this has more to do with static and not grounding, right? Louis: I tried that, didn't do a thing. I can say this, the snapping noise seamed consistent as if its sometimes more of a pulse, although it can be random at times.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-26-2010 01:37 AM                     I take a piece of 12awg solid and hammer it flat then laminate it to the top of the cell so that the lip of the copper is just slightly forward of the cell so it is just slightly closer to the film than the cell face  |  IP: Logged Gavin Lewarne Master Film Handler Posts: 278 From: Plymouth, UK Registered: Aug 2009 posted 01-26-2010 04:24 AM                     we had this exact issue on our pair of westars with jaxlites and a cp45. This to checl: The preamp on the offending machine, is it an XLA-650 A or B? We had 2 B units (difference being they supposedly have balanced outputs) and one machine developed crackles. I eliminated everything except the preamp, so i swapped it for a A varient i had spare (unbalanced version). Then changed the jumper in the CP45 to Proj 2 Unbalanced, did A-Chain and cracking gone for good. I have swapped out the other B preamp for an A now as well, and i have to say our sound is excellent now compared to what it was before.  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 01-26-2010 03:48 PM                        Gordon: how did you laminate the wire to the cell? Thanks Bernie  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-26-2010 06:41 PM                     I'd get rid of the Jax Lights... Don't try running BACP scanners off that Kneisley supply either...  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 01-26-2010 06:48 PM                        getting rid of the jax lite really isnt an option. Too much money to replace for 2 projectors.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 01-26-2010 11:41 PM                     I used some epoxy to glue the shield down LAP associates used to make nice split cells that had a shroud and even vernier adjustment  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 02-06-2010 11:29 PM                        Okay, so get this one. I did everything that everyone suggested. I even ran a leg off the power supply to the chassis of the soundhead. The popping/clicking sound has subsided, but it shows up every now and them. BUT, tonight I ran a hour reel of a film and I was getting this pulsating wooshing sound. When the projector is running with out film, its not present. I spun the sound drum by hand to where it was turning by itself, the sound was recreated. Now what is that about? Seems like I'm picking up the bearings on the drum in the sound. Why? Is it static electricty being cause by friction in the bearing and now that's being discharged? Its strange its only the left machine. Right machine, same set up, is fine.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-07-2010 12:20 AM                       Are you sure the solar cell or its bracket is not touching the sound drum? Try temporarily unscrewing the bracket baseplate from soundhead. See if the sound goes away. You could also have a solar cell with an internal short on one of the 3 wires.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-07-2010 03:11 AM                     some bearings have caused issues as well  |  IP: Logged

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