ghosting DMX

dmx

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I'm doing a contract gig which is being produced at a small local theatre. Funny thing is, when the lighting console is disconnected/turned off, the dimmers will randomly strobe. There is a stand-alone architectural control system installed, which is incorporated with the stage lighting, but as I'd mentioned, the problem is not when both controllers are on, but rather when the light console is off.

Anyone seen or had this before? It's an all DMX system (no protocol converters), 2 universes, with an 8-way Gray Opto-Splitter. The splitter is normally powered down, but has no apparent effect on the problem (problem exists with splitter both on and off). Never have any problems with the board on, but that results in the console being left on 24/7.

Is there maybe a line not terminated? I'm stumped.

Thanks for looking.

--Matt
 
yes i have see this before what type of dimmers???
we have 4 SD6 dimmer packs from strand and dasey chained toghether they can have some fun not kool
 
Dimmers are ETC Sensor, 2 racks. Meanwhile, I'll start looking through schematics for a bad connection. Thanks!
 
Try unplugging your DMX connection from the console, and then power off your console and once down plug it back in--does the situation repeat then? Also--what is the console? That info may help folks help you...



-w
 
What do you mean by "strobe" exactly? Is there a light that pops on, or a quick, pulsing frequency type strobe? Does changing the preset on the unison system help or hurt the situation?

Depending on the wiring, you could have a faulty DMX transceiver chip in the Unison processor. Since it doesn't flicker from the console, I would concentrate on the Unison system. Try some different presets if you have that option and see if it still happens. Could be an odd programming thing at the processor.
 
What do you mean by "strobe" exactly? Is there a light that pops on, or a quick, pulsing frequency type strobe? Does changing the preset on the unison system help or hurt the situation?

Depending on the wiring, you could have a faulty DMX transceiver chip in the Unison processor. Since it doesn't flicker from the console, I would concentrate on the Unison system. Try some different presets if you have that option and see if it still happens. Could be an odd programming thing at the processor.

I remember someone talking about this issue before. Do the lights just pulse when you turn the console off or do the lights constantly strobe while the board is off. The DMX512 protocol doesn't have a way to communicate the end of the stream so it's not exactly pretty when the stream is ended which might result in some lights getting bumped to full or other combinations when certain consoles are turned off, especially if the rack is set to hold last look for X amount of time.

Or maybe this isn't the problem that you're having at all.
 
First, thanks to everyone for their replies and advice. Last night I shut the board down, disconnected DMX, and later re-connected with the board powered off.

With the console powered off or DMX disconnected, the stage lights will fade in and out (maybe strobe was the wrong word). This occurs at varied intervals and channels.

Then Unisom system runs 24/7 and is still functional with/without the board on. I will try disconnecting the Unisom system tonight to further troubleshoot.

Adding another wrench into the mix, I should probably have mentioned that there are DMX connections throughout the grid, 1 in the booth, 1 in the house, 1 on the SM's console. There are 2 universes run, but the dimmers are all configured on universe1, with universe2 being reserved for the movers.

Thanks! --Matt
 
Hmmmm.... not sure but you may have a Unison or CEM problem....something in the chain when the console is not taking precedent for signal is looking for or randomly getting some kind data. Do you perhaps have an IR-RFU or similar connected into the system? Have you recently replaced any of your DMX lines or added in ANY new components?


-w
 
I know exactally how u feel. We have almost the same setup that u do. I have seen this happen before and I can't explain it either. But with ours it's just one light that turns on... We call it the ghost light... My only question is why are u un-pluging the universe?
 
I've had a similar problem with units/dimmers ghosting on after our Ion shuts down. We typically resolve it by resetting the CEM and walking away. Others have solved it by clearing the faders, unplugging DMX and shutting down.

However this isn't with any Unison control in the mix, which from my experience on another stage I know can make things interesting...

I know on our main stage you can reset the sensor racks that control the theatrical units separately from the Unison rack that's controlling our house lights (that and the Unison has no reset). If you're able to do something similar I would say try that and see what happens.
 
I realize this is an old thread, but it doesn't appear the problem was ever resolved. See the wiki entry DMX death gasp, and follow the links, but that usually doesn't contribute to dimmers strobing, or fading up and down.
 

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