Backstage lighting control system on the fritz

I recently came into managing a high school theater that is used frequently for community events.  As typical, the school district has no interest in expenditures for maintaining the facility.  While it's a nicely designed and equipped theater, the joke in the community is how half the gear in it doesn't work.

The ETC Express 24/48 controller and stage lighting system work just fine.  What doesn't work right is what appears to be a custom ETC backstage/orchestra pit/catwalk lighting system as seen in one of the attached pictures.  When energized, at least some of the zones turn on and off on their own accord.  Everyone says "all" of the zones do this, but I have not yet confirmed that to be the case.  The district electrician says he doesn't know what the problem is and can't be bothered with additional request for fixing this.

I have also noticed that some of the multi-button wall switches work correctly and others don't.  That is, the ones that work correctly appear to toggle correctly since the indicator lamp turns on or off when the button is pressed.  Ones that don't work correctly don't change indication when the buttons are pressed, or when one button is pressed, a different or even multiple other  indicators go on or off on the wall plate.  Our wall plates vary from 2-button on up to 5-button models.

My question for anyone familiar with this system and repairing it is, does this random light switching happen because of faulty wall switches?  Or are the wall switches faulty because the controller module they are connected to is faulty and the random switching switching also happens because of the faulty controller module?

Any tips that can help pinpoint the issue will go a long way in getting repair parts and our electrician to get things fixed.


  • I have seen many systems that look very similar, but the core gear varies as with the age of the installation. You need to dig a bit further into the parts to know how to trace the issues. The upper slider and buttons, as well as the 2 button station shown are part of the Unison Legacy system, if they are at least 10 years old. They are computerized remotes that tell a central processor what to do. Replacing them might take a service call from an ETC trained technician.

    The worklight buttons are simple switches that may feed into the ETC Unison system or be completely isolated and go to something else by GE, Green Gate or a dozen other brands. These buttons can be replaced individually if you can find the parts. Knowing what relays they connect to is critical. 

    The good news is that ETC may have complete drawings of the system. Call tech support to request whatever they have. If you have some kind of label or sticker on your dimmer racks, that info might help them find your project. They can help with parts, diagnostics and finding a local technician. Much of this stuff is far beyond a maintenance tech. 

    Seeing a Unison button station half covering a 2 gang box tells me the installation was not perfect. Whether this was a minor contractor issue or if the whole project was a retrofit would be good to know. Most school districts keep copies of the construction drawings for the original buildings and major remodels. See if you can get a look at them as well. Note the dates! 

  • Thanks for the prompt reply. Please understand that I’m flying solo on this. No one seems to think it important enough to do anything about. Yes, I know there would be prints somewhere but again no one cares. My position as the community event theater manager is lower than the custodial staff. They won’t even give me a key to the handicapped elevator.

    The building is about 25 years old. I don’t know if this ETC system goes back that far, but it looks original to the building. I have not found any sort of programmable user interface. There’s no other visual sign other that the hinky wall plates of this possibly being a retrofit. 

    Attached is another picture of just the section on the wall controller that’s having the problem. Behind this switch panel are a number of circuit boards that these switches are wired to. I intuited that the unison wall switches also came to this box and tied to these cards but now that I think about it, I didn’t actually confirm the wiring paths.

    The low voltage output from these cards enters a conduit that goes up two floors to a large panel containing a large barrier strip and twenty or so relays with contacts wired to the neighboring breaker panel.  So power from the breakers goes through the contacts and on to the actual lighting fixtures or outlets and the coils are energized via the low voltage from the boards in the controller below.  The unison wall switches have no special programmed functions other than simply toggling the zone it’s wired to on and off. 

    Im pretty confident I can persuade the electrician with a case of beer to come over and solve this problem if I have a good hint at where to point him. So again, if anyone has any experience with a system of this vintage and what usually causes a zone to turn on or off randomly of its own accord, it would be immensely appreciated if you were willing to share that knowledge. 

  • Not seeing another photo.

    Do you have a really short dimmer rack? Or a small box painted the same tan as the main dimmers? Some of this stuff

  • It is going to be hard to get to the bottom of much without looking at the ETC job prints which will have the wiring schematics for the stage management panel. Calls to ETC support cost you nothing and we will likely be able to figure out your job number based on city, state and name of facility.


    NOTE: if you do not have access to a lot of areas, it will be hard to troubleshoot. You will need to find the dimmer room which will most likely also have the architectural processor.

  • In what city are you located?

    ETC: (800)-688-4116, ask for lighting technical support.  They are in Wisconsin and on Central Time.

  • Thanks for all of the replies.  I'll have to come up with some time to reach out to ETC, but even without prints there have to be ways to troubleshoot to nail down the issues.  The problem is not with any of the house dimmers or controls.  The problems are with this section of the controller.

    As I've pieced together, it appears that the yellow buttons are momentary and they toggle the state of the switching logic on the circuit boards to which they are attached which then energizes the appropriate relay upstairs.  Toggling the state of the switching logic is also what the unison wall buttons do.  If you sit and watch these yellow buttons, you'll see some light up or go dark all by themselves and of course the circuit they control also turns on/off.  Specific areas I know of that switch randomly are at least two of the three orchestra pit circuits and one or more up in the catwalks.

    Take the orchestra pit.  My gut says to disconnect the malfunctioning Unison wall switch and see if the random switching continues.  If it does, then I would try swapping the logic board with an identical one that I haven't seen the issue occur and see if the random switching now moved to other zones.  But, of course I was hoping someone here had experience with this sort of problem and could offer a suggestion that would target us to the solution because any other scenario requires enough labor to make getting help difficult.

    Thanks for everyone's suggestions again.  Yes, I do see the value in getting schematics and will make an effort to obtain them.  It's just frustrating to have great equipment in the facility that is broken and no one seems to care enough to make it right.

  • Possibly but the section of the controller I'm referring to does not involve dimmers, and the more I ponder it, the more certain I am that the section I'm talking about is completely discreet and doesn't involve a programmable controller.

    Sorry, I thought the picture posted with my previous post but obviously it didn't.  It's the picture down below.

  • IM me the name and address of the facility and I see if I can find the prints.

    You seem to indicate that the stage management panel switches output wires that go up though a conduit to a relay panel for direct control. Maybe they do but that would not be the norm for and ETC system based on what I’m seeing on the panel. ‘Normally’ the local switches would be wired to a local Unison contact interface station with a local power supply. The switch closures on the interface station would be translated into the Unison control protocol and get sent to the Unison processer. From there the data would control Sensor dimming racks, Unison dimming racks, and/or a DMX control relay rack.

    Undo the screws on the front of the stage management rack and pull the panel out (or the rack might fully swing open to see the backside of everything). Look to see where the wires from the switches go. I’m guessing they go to a terminal strip and that the terminal strip is wired to a Unison contact interface station.

    Once again, IM me the name of the facility and the address and I’d likely be able to tell you exactly how it is all wired.

    Mike Meskill

    Global Technical Service Manager


  • Mmeskill below has it right - most likely you’re seeing those small wires go into the pipe, and the same wires come out of your pipe in the GE/Wattstopper relay cabinet, but there are likely a ton of wires in there and it can be a real pain to sort through all of them to figure out which goes where. It is possible that those analog wires/switches do in fact directly trigger the relays, but there is also a contact interface triggering those relays, possibly in parallel. Unfortunately, where I’ve maintained this exact type of system in the past, the fail point over time is the Unison Contact Interface card(s) Or (UCI). If that is the case, taking he Unison Legacy wall stations WILL NOT alleviate your random switching issue since they are jus digital connection back to the processor, and the UCI is just another node on that system. If you can find the UCI (probably in a standard equipment rack in a 2-3RU tray or in a black wall-mounted box with white lettering Unison Contact Interface) you could pull off the green connectors with all the analog wires or pull the white/black LON connector off and shut down that board which probably will make your random issue go away, but will also eliminate wall switch operation of your relay circuits from any of the Unison stations. 

    The bad news... I’ve got two systems of this type and vintage that I originally retrofitted (THE ETC IS RELATIVELY NEW, prob 10-15yrs, the relay system is original to the building) so I really know the guys of them, with the exact problem, and it has taken me multiple trips and many hours each trip to get this far in the troubleshooting. This is a bear. In those systems we have determined how we coils cobble it together for now so it doesn’t misbehave much, but the best answer for the ones I’m working on is to replace the relay panel with a DMX controlled relay panel (probably not an easy ask in your situation). Replacing the UCI may solve it, but the last UCI I sent in from one of those systems, came back as “no issue found”...

  • So for those keeping track:

    I’m in contact with the user directly. Found the prints and the system wiring is that the SMP (house and works) are on Unison (contact interface stations) and feed to a DR6 rack. DMX flows from there to 2 @ SR48 racks and then to an ILC relay panel with Quanta Elite Programming (the relay has DMX in and has 20 Work light Circuits out. So the issue could be in a few different places.

  • Glad to hear it! 

    Part of why we rave about ETC support.