Fixtures remain on after board is turned off

[JVV]

Hello,
In our black box we use a Leviton MC 7000 series light board and some fixtures will continue to glow after all the faders are pulled down to zero. Even when we unplug the DMX, the fixtures will remain on.

I'm curious because when turn off the light board in the Main Stage theater (an ETC ION), any lights left on will eventually fade out.

Is there an explanation for this? I can provide Dimmer types if that makes a difference.
Thanks,
JVV

 

[TheTheaterGeek]

Yes, What dimmer types are they?

 

[BillConnerFASTC]

Is there an architectural control system as well? A common cause of this is accidently recording a level for that channel in an architectural preset.

 

[RideTheSquirrel]

Are these LED instruments or are they incadescent? With LED instruments had this experience that some of these fixtures will stay illuminated once they are no longer receiving DMX signal telling them to be at 0, because the onboard programming takes over to whatever preset they were before receiving DMX signal.

 

[FMEng]

If its just a very faint glow, it could be a dimmer designed with filament preheat. The theory is that it reduces lamp failures, although we've debated that. On some dimmers, there is a calibration adjustment for the bottom of the dimming curve. It could be a little off or adjusted deliberately for preheat. Ask the manufacturer.

 

[TJCornish]

Most of the NSI 7000/7500 series boards I've worked with have many miles on them and faders that are worn out and no longer turn off all the way. Do any of the channel LEDs glow a little bit? Have you pulled the master fader down as well as the channel faders?

Many DMX devices - especially the less-sophisticated ones just stay put when they lose signal. Your other room may have a more intelligent controller that gracefully handles loss of DMX.

 

[JVV]

Yes, What dimmer types are they?

Okay, more information...

The MainStage Dimmer Racks are ETC Sensors. The Black Box is Leviton a-2000.

There is no Architectural Control System in the Black Box.

These are all Incandescent Instruments.

It is never a consistent instrument or consistent level that the lights remain on at. I am sure that the faders are not pulled down to absolute zero EVERYTIME the kids unplug the board. And they are instructed to make sure the Master is at zero as well before they put the board away... but of course that doesn't always happen.

I guess the fix to the problem is to be extra diligent in making sure all lights are completely off before packing up for the night, because the Dimmers in that room will not fade out once the board is disconnected.

Thanks everyone for the questions to help me see this problem clearly.
JVV

 

[JD]

Is the rack programed to hold the last value if DMX is lost?

 

[Mac Hosehead]

Is the rack programed to hold the last value if DMX is lost?

I encountered this dimmer panel at a high school once. It seems more like an architectural dimmer panel that can also do DMX. I am not aware of a DMX time-out setting in this panel. It will LTP with wall panels but I don't think there are wall panels. I would recommend putting the console in blackout mode when disconnecting DMX.

 

[SteveB]

Sounds like the rack is holding DMX as the console gets powered off AND not all the faders or master are off.

You can set the racks to not hold last look, but I wouldn't. I have my racks set to hold as long as possible as it's a backup in case the console loses power, etc...

So then it's a matter of operators being trained to really, really drop the grand master before shutdown.

 

[Brandon Paul]

I have had experience with ghosting on house lighting. This is always an obvious, but make sure your students are executing [go to] + [cue] + [0], then zero the master. If they are still ghosting I want to assume it's a dimmer issue.

 

[BobHealey]

I have had experience with ghosting on house lighting. This is always an obvious, but make sure your students are executing [go to] + [cue] + [0], then zero the master. If they are still ghosting I want to assume it's a dimmer issue.

I've had lights come on, even with an Express completely cleared, due to noise on the data line when the console's powered down. Couple that with hold last look forever, and viola, nuisances.

 

[SteveB]

I've had lights come on, even with an Express completely cleared, due to noise on the data line when the console's powered down. Couple that with hold last look forever, and viola, nuisances.

Yeah, that was a known bug, never fixed, on Express/ion line. We learned to unplug DMX with no values, THEN power down.

 

[Mac Hosehead]

Yeah, that was a known bug, never fixed, on Express/ion line. We learned to unplug DMX with no values, THEN power down.

The reason fixtures might "pop on" when turning off the console is because the DMX stream is being interrupted mid-frame and the dimmer rack interprets it as a light level. This should not happen on consoles that have a shut-down procedure.

Time to digress:
I heard a story from the local about a prankster who put a battery lantern in a fresnel and then took it to the foreman saying he had a light fixture that wouldn't turn off. As the story goes, the foreman just said to tag it and put it in repair.

 

[SteveB]

The reason fixtures might "pop on" when turning off the console is because the DMX stream is being interrupted mid-frame and the dimmer rack interprets it as a light level. This should not happen on consoles that have a shut-down procedure.

Well, maybe "bug" is too strong. It was certainly a "feature" that you learned could occur (but not always). I think what drove folks nuts was you could drop the GM, which would - in theory, drive DMX levels to zero, and it would still occur.

 

[JD]

The infamous DMX "Burp" that happens on shutdown, much like the "Thump" of an old power amp being turned on or off. Even if all 0's are set, the burp spits out random values. Had a board that did that, so I made a DMX "mute" switch. simple DPDT that switched 2 & 3 off the board output and shorted them to pin 1.
So, in one position, 2&3 loops from board to stage, in the other the board is disconnected and the stage feed is muted to pin 1.
In my case it worked great. Simply hit the mute switch and shut off the board.

 

[Painterspoon]

Oh my God - I have the same problem in my high school drama room - Leviton and incandescents. I thought we had ghosts! haha.
Glad to read some explanations (even though I will have to re-read them to fully understand what the heck is happening). If the kids unplug the lights without bringing down the master, two of our Lekos (newly wired in with a new dimmer box) stay on. So annoying!

 

[RonHebbard]

Oh my God - I have the same problem in my high school drama room - Leviton and incandescents. I thought we had ghosts! haha.
Glad to read some explanations (even though I will have to re-read them to fully understand what the heck is happening). If the kids unplug the lights without bringing down the master, two of our Lekos (newly wired in with a new dimmer box) stay on. So annoying!

@Painterspoon A couple of possible options for you: You MAY be able to change a setting on your dimmer pack and tell it NOT to hold on to the last DMX values it receives, alternately whip your students to ALWAYS pull the master down to zero before shutting down. Many / most dimmer racks and packs will hang on to the last DMX values they receive (Thinking they're doing you a favor rather than plunging you into black) Often there are selectable hold / delay times varying from zero, no hold, to 30 minutes or more all the way to hold the last value forever.
Toodleoo!
Ron Hebbard.