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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 02-09-2010 10:59 PM                        So here's an update. Its the weirdest thing. Checked all connections, checked to see if cell was hitting the drum. Then I found on the gear side that the cell wire was hitting the casting of the sound drum and when I pulled out the pre amp the cell wire rubbed against the balance drum and it made the sound even worst. So evidently the cell wire is picking up all different kinds of noises and introducing it into the pickup. So the question is, what is the best way to sheild the wire from the cell? Is there a better place to put the preamp instead of the soundhead casting? Should the power for the preamp come off of the exciter lamp or should it be a separate power supply? Strange little thing, these Jax lites. What's the best wiring for wiring the pick up? Can it be two independent wires for left and right input of the cell?  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-10-2010 12:28 AM                       Is the cell wiring shielded or just 3 wires running loose to the Jaxlight? It should be 3 wire plus shield starting as close to the cell itself as practical. The shield needs to be connected at the preamp end. The wiring should be secured so it does not move physically as this will induce noise when the signal is so low as it is with a Jaxlight. The light output from the Jaxlight is much lower than what you had with the old exciter lamp so it's more sensitive to noise.  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 02-10-2010 06:40 AM                        Its just the 3 colored wires coming out of the cell. There is no shield nor is there rubber insulation. That would explain things a bit. Any suggestions on the best way to shield those wires? Thanks Bernie  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-10-2010 08:33 AM                     Almost any sheath will do. Including heat shrink tube but don't apply the heat...let the tube remain at full size to space the wires off. Note you could even use the stripped off jacket from another cable...it really doesn't matter. Steve  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 02-10-2010 10:11 AM                        Thanks Steve, I'll give that a try. So I still have 2 questions then: Should the preamp be at the projector end or processor end? What kind of wire is best to connect the cell? I have a feeling that all of this will clear up my popping sound. I'm still getting a pop (similar to when a splice goes through) when any electric contact happen, example, when the C/O opens, when the curtain/masking opens and closes. You hear a pop. I'm assuming this would case that too. Thanks Bernie  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 02-10-2010 02:21 PM                        I know you have a $$$$ issue, but the sure cure for a Jax Lite making noise is anything else and the Jax Lite in the trash barrel. You not only won't be sorry, but you will have to do it eventually anyway. Louis  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-10-2010 02:45 PM                     I definitely with Louis on this one...part of your problem is the JaxLight. We will need to know more about your sound system to help with the other electrical pops. Those that use unbalanced or ground referenced inputs tend to be more prone to them. Also, the quality of the ground on the sound system and just what else is on that ground will affect it. Steve  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 02-10-2010 03:52 PM                        Hi Steve, The system is 2 projector setup with RCA 9050 Sound heads. The cell goes to the jaxlite preamp. The preamp is powered by a tap off the exciter lamp which is powered by a kniesley exciter supply. Then a leg of the exciter lamp goes to the projector casting, like the jaxlite manual says. From there the sound cables go though a seperate conduit to the back of the soundrack about 10 feet away. The conduit is about a foot below the high voltage trough. The shield is connect at the preamp but not at the cell input on the back of the processor. The processor is then a CP45. The CP 45 outputs to a consumer Yamaha 6 channel input amplifier (I use this so I can also run DVD and Cable TV through it). The rest of the setup has Simplex Supers and the lamps are ORC 1000. I'm using Eprad Co-operators for automation. (I know, it's a grave yard but it works) Unfortunately, since its a house, I'm using the same ground, so I'm sure there is something going on there. Everything is grounded back to the breaker box. It doesn't matter if I ground the processor or not. I get no hum in the sound, unless I connect the cell's shield to the processor, then it hums like a bitch. I was curious and thought because the left machine (the one that is problematic with the jaxlite) came on line after the right machine, I thought maybe it had something to do with that. It didn't. I removed the left machine's input wire. The pops went away for about a min or two as I was testing the equipment. The pop came back even when only one machine was hooked up. The pop is more predominate on the closing opening of the curtain and masking, C/O's, Automation impulses (any relay pulse, cues, starts, etc.) I do not get a pop, though on the soundchange over relay (latching relay), any light switches in the booth or even the 110v framing light switch. (frankly those are the only things that aren't grounded, they're all two wire). Obviously, it has something to do with the ground.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-10-2010 06:16 PM                       How long are the cell wires going to the jaxlight preamp? Any more than a few inches and you should put them on a terminal strip and make a transition to a shieled cable. As to where the best place for the Jaxlight, the closer to the cell the better. There were a couple of different models of the preamp, unbalanced out and later, balanced out. I don't disagree with Steve or Louis about the need to upgrade, just trying to make it better. From the sound of it, you have more than one problem with pops. Best way to troubleshoot them is, disconnect the cell wires from the Jaxlight input and see what pops remain. If still there, disconnect the output from the Jaxlight. Also, do the pops show up in any other formats, non sync, etc? That's enough for me today. You have your homework assignment  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-10-2010 06:59 PM                     First off...the CP45 should be grounded...period...get a good bond on its chassis. The shield of the cell wire should then be connected there...if you get a hum...move on down to the JaxLight preamp...it is on the same reference as the CP45? If not, bond it...preferably not with the shield but with a dedicated wire of 18awg or larger...however, while troubleshooting, the shield will do. Lets start with that. Steve  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 02-10-2010 07:16 PM                        Steve, What exactly do you mean by "same reference"? Sam, No pops anywhere else. I removed the cell inputs and with it in any of the optical formats I get no pops what so ever. So its definitely being picked up in the cell wires. The cell wires are short and were extended about 4 inches to reach the preamp Thanks Bernie  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-11-2010 12:36 AM                     You might try braiding the short cell leads  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-11-2010 05:22 AM                     Same reference = same ground potential. Using an 18awg wire will do that for you...tying the shield at both ends will do it too but compromise the electrostatic shielding and due to its smaller gauge, may not bring the potential close enough (have a bit of a ground loop of its own). You don't want ANY current flow on the shield...just the noise to have somewhere to drain. Steve  |  IP: Logged Bernie Anderson Jr Master Film Handler Posts: 435 From: Woodbridge, New Jersey Registered: Apr 2000 posted 02-11-2010 01:26 PM                        I think I'm gonna just start over and rewire this machine using everyone's suggestion, because its all wrong based off your answers. I started on this machine years ago and just within the last year got it running. Steve, you're just saying attach the shield (or 18 awg wire) to the processor (body of the connector) and if it continues to hum connect it to the shield connection at the jax lite preamp, but either way, it must be connected to the processor. Basically, there no where for crap interference to go except into the cells input and that's what's causing the popping. The cell wires are not braided and are hanging loose to the preamp. And then I used crappy Radio Shack w\2 conductor with shield wire too. Is it okay to use (2) 2 conductor and shielded wire as long as the shields are connected? It doesn't need to be all in a 4 conductor single cable, right?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-11-2010 02:57 PM                     Yes, more or less. A shield must drain to ground...that is how they shield. In a perfect world they can connect at both ends of the cable if both ground potentials are the same. It is safer by only terminating at one end. At the cell end, you don't have a good ground reference and you do at the processor end, typically. To minimize ground loops, it is best to bond the devices to the same ground...the bigger the wire gauge, the better the bond and the closer the potential. What you don't want to do is then bond that to the projector case. You want the JAXLight preamp to be an extension of the sound processor..as well as the cell itself. While you are doing this...seriously ...price out the cost of a basement reader system...and save up...they just are not that expensive. Steve  |  IP: Logged

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