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Unique & Glaciators not responding to DMX


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Hi. Hit a brick wall with this one...


I have 2 x streams and a unique 2, which just aren't recognising DMX at all in this venue. Last week all was well, got them out here and just nothing. They all happily work manually, but dont switch to DMX when plugged in.


Here's what I've tried so far:


Separate DMX feed, different places in different chains.

DMX direct from my swisson.

Phase reversed DMX direct from swisson.

Un grounded DMX direct from swisson.

I've checked all internal fuses.


(the swisson definitely works and happily controls other things)


The fact it's 3 units leads me to think its a local power issue or something, but everything else in the rig is fine, I've re run power from various different supplies and no changes.


I also have a dead unique which I can't decide if it's related or not, seems to be getting power etc and all fuses are good.


We're completely stumped.

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Well.... The one constant in this is the Swisson. Have you tried sending DMX from another device? I once had a similarly puzzling problem on a zero88 Sirius 24 with the inverse leg of the DMX transmit broken. In the desk. Worked for some devices, and not for others.


I've also come across problems with some homebuilt DMX devices and a Strand GSX, which output surprisignly long DMX break signals....


This is why something like a Dr. DMX or similar Cheap DMX tester (or even a £10 MagicDMX dongle and a laptop) really is your friend for test purposes.


Even one of those handmade DMX test terminators tends to show up missing DMX legs pretty well.

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...DMX direct from my swisson...leads me to think its a local power issue or something...

It's certainly something but it's not local power. Your Swisson is battery powered so that eliminates any earthing issues.


If you've tested them as simply as...



Swisson -> Known good DMX lead - > Suspect units



..and they still don't work then I'd be looking at them having been borked at the end of the last show.

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Well.... The one constant in this is the Swisson. Have you tried sending DMX from another device?


This is why something like a Dr. DMX or similar Cheap DMX tester (or even a £10 MagicDMX dongle and a laptop) really is your friend for test purposes.


The pretty expensive Swisson DMX tester is my 'other' device, being used to eliminate patch from the Ma2/ broken cables / etc. I tested the swisson on other units too to make sure it is working correctly.


I can't find anything internally wrong with them, and it would be mighty strange for 3 units to have the same problem on the same move, and never happen in the last 6 months of touring.


Thanks for the answers though.

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Silly me, hadn't thought of Swisson the dimmer people- for some reason read swissonic which used to be a cheap china import brand of audio gear....


I assume from what you've stated that these units previously worked OK with the Swisson connected directly? And your desk is a GrandMa2, which also doesn't work with them, now, but previously worked OK, and has been tested in this venue via the existing DMX distribution set-up, correct?


I assume you've used the Swisson to test the output of your DMX distribution to make sure that's OK as well?


I'm also assuming that you've tested each of the glaciators and the unique on an individual one to one DMX connection, not just the chain of all 3 devices. A suffciently defective DMX receiver chip in one device can pull down the whole chain up to whatever DMX splitter/distributor you've got.


I guess it could still bean RFI issue messing up the DMX receivers, but this would be very weird- practically unheard of unless you've got some _serious_ RF power somewhere in the vicinity (like a 50kW AM transmitter in the next room or something).


Or something totally leftfield, like powerline network adapters and inadequately filtered power supplies. That would be pretty weird, too. Especially given identical behaviour with devices from different manufacturers.


Only other power-related thing I can think of, given that you're touring an ice show... dirty power caused by electronic 3-phase motor inverters for chillers?


I guess it could be a local power issue, but a bit unlikely given that the equipment works perfectly on manual operation. I assume you've metered the local voltage and it's not wildly out of spec. What kind of power are you getting in your current venue, given that you're on tour- 240/415v, 230/400V or something weird and American? I'd always be worried about crosspondians giving me something they called 240v given the potential for supply weirdness anything over 120v entails over there- could be anything from 208v to 277v depending.


It's obviously not going to be a transmitter or earthing problem with the battery-operated Swisson, if it works on other stuff _and_ previously worked fine with these devices.


The only other possibility is defective DMX receivers. Static or overvoltage damage?


Multiple devices all not working, even when not connected to each other, points to somebody having managed to jam mains voltage or a few kV of static up a DMX cable at some point. Which is why you hope for socketed DIP DMX receivers and big fat through-hole transils rather than something tiny in SMD.

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So if you're interested, it was indeed the DMX chips on all 3 units that had gone.

Nice to know it was something obvious in the end, though I'd love to know how it happened. Any scrollers in your rig? The only time I've seen damaged DMX chips myself is when somebody managed to short 24v scroller power onto the data pins on the same cable.... didn't damage the receivers in the scrollers but did destroy the receiver chip in the scroller PSU somehow (the PSU has a built-in tee repeater for the scroller chain).

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We're stumped as to what did it, but only when you mentioned static did we realise they were in their own chain last week, so we finally had a common factor. There are no strollers around, but 3 pin comms and also pyro, so it's feasible that something was plugged in during the out. I guess we'll never know.


Cheers all.

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