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    LightGuy145
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Sensor CEM3 D20 Coupled Dimmers and Swapped Circuits

I have a standard 96 dimmer rack of all D20 modules with a new (within the past year) CEM3 controller running 1.6.1. This is a fixed dimmer-per-circuit rack in a auditorium.

Note: For both these problems I have tried swapping dimmer modules around and powering down the separate architectural control system. I've also reset the CEM. No change whatsoever. The problems exist no matter what controller is sending DMX to the rack (architectural controller, Express 48/96, PC controller, etc). This leads me to believe it must be an issue with the dimmer rack itself.

Problem 1 - Coupled Dimmers

Two sequential dimmers 75 and 76 (in the same module) will not turn on unless they are both on together. They aren't configured for dimmer doubling. In fact, I don't see any difference between their dimmer settings and any of the other properly functioning dimmers. Does anyone have any idea what might cause this behavior? I thought maybe the module was going bad but it happens even after I swap it out with another properly functioning module.

Problem 2 - Swapped Circuits

DMX address 58 turns on circuit 70 and DMX address 70 turns on circuit 58. I've double checked that both the circuit assignment and the patching are as they should be... DMX address 58 is assigned to circuit 58 and circuit 58 is assigned to the correct lug. Same goes for circuit 70. How could the swapped behavior therefore be possible unless the circuit wires going into the modules were at some point swapped? It seems unlikely this would have happened as part of the installation of the CEM3. It seems even less likely that anyone has been inside the raceway for any reason. I know I can "solve" this problem by reassigning DMX address 58 to circuit 70 and vice versa, but that doesn't offer any explanation as to why this problem began after the CEM3 was installed. I need answers! I need the universe to make sense!

  • Hi LightGuy,

    Hm - those are some interesting ones. The first thing I would say is that if the CEM3 is new within the year, obviously your system is covered by warranty so feel free to contact ETC to get a tech out after some troubleshooting!

    Problem 1 : Are you just noticing this on the outputs, or if you go to the rack and turn on one of those via the set levels menu, does it still not work until they're both on? Does the behavior of the signal LEDs on the front of the module match that - so that neither signal LED comes on until they're both on? That might point to a hardware fault, although an unusual one. I'd also check that the CEM3 is receiving levels as expected - go to [About] -> [Source Info] and check that levels show up as you would expect for those dimmers.

    Problem 2 : I'd also check this by looking at the [About] -> [Source Info] screen, and see what happens when you bring up DMX58 - does the source info screen show it as 58, or 70? It'd be pretty strange for a hardware fault to swap entirely random dimmers, so I definitely suspect configuration for that one.

    Incidentally if you have a PC or ETC console on the network and you install Net3 Concert, you can configure your racks from the PC/Console, which will make this easier to see than from the small screen on the front of the CEM3 - you get a table view of the dimmers in your rack including DMX addressing which may help figure out what's going on.

    Good luck and hope the [DMX] universe makes sense soon.
  • I agree with Tom on get with the factory to get this checked by a tech if under warranty, but a couple of things do come to mind that could have happened with just a CEM upgrade. This assumes that no high-voltage wiring was touched during the upgrade. There could be an issue with the ribbon cables not properly seated, or a bent pin on the terminal of the backplane, though with the 75/76 issue I would expect that to manifest as a "either turns both on" rather than the described "both must be on for either to work". However if this is a phase-balanced rack I would point out that all four of these circuits noted are in the same phase and what looks to be the same ribbon cable, so that'd be where I'd be looking.

    75/76 issue: Possible this could be some kind of weird hot/neutral swap or open neutral if these circuits are in the same piece of distro, but I would have expected that to have been noticed long before this upgrade if the rack hasn't been changed (unless something got jostled while wrangling new cables or the backplane in to place), and usually that shows up on "sequential" circuits in different phases. Probably worth putting a GamChek on the circuits to check that the wiring is all as intended.

    If Tom didn't mention it, if you choose to look into this yourself, make sure to fully power down the rack before poking around with any of these items as you're going to be removing modules to do so. But again, if a factory-authorized tech did the upgrade, I'd have them come back out on warranty to check into it if you've got to go deeper than what Tom suggests.

  • Thank you for your replies. I was able to download the Net3 Concert software and use it to more easily assess the dimmer rack configuration. I was also able to send the configuration to tech support and do some troubleshooting with them. Review of the rack configuration showed that the patching was as it should be. Cycling power to the whole rack made no difference. Refreshing the rack configuration with the quick setup made no difference. I believe that using the "Set Levels" in the CEM resulted in the same behavior for 75/76 as an external controller. I believe that the behavior of the signal lights matched what I described; neither light turned on until they were both on.

    Given all the factors and when they manifested we are pretty certain it is an issue with a ribbon cable or bent pins on the back plane, not an open neutral issue with any of the high voltage circuits. It is apparently possible that the issue could be with the new back plane hardware installed as part of the CEM upgrade -OR- the original hardware beyond that which remained in place during the upgrade. We won't know for sure until a tech looks at the rack.

    We were able to get through the shows we were doing by just keeping 75/76 assigned to the same channel in our console and treating them as twofered together. We also flipped the 58 and 70 in the dimmer rack patch so the numbers at least correspond to the proper circuits until the problem is fixed.

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