Corrupted DMX

[Richard CSL]

Ok this ones got me beat. I have 8 Queen spot Moving Heads and 16 showtec par 36 leds on a line from a showtec DMX splitter. on another line from the same splitter I have 10 soundlab scanners G017S a fusion 6ch dimmer pack and 10 showtec par56 leds.

on another line from the splitter I have 3 ART 3200 lasers.

 

So thats the set up. I have had trouble recently with flickering mainly the MH and par36 but also the other line, oh and the last laser no controll at all.

 

So yesterday put a line terminator on the MH & par 36 line, seemed to solve the MH and par 36 problem or so I thought. still no lazer control at this point, so last night removed the last lazer took it up to the DVC2 box and it worked fine. I then started to eliminate one head at a time on the MH & par36 line, discovered one of the Queenspot MH causing the flicker, now when the DMX leads plugged back into the MH with no power on I get flickering again. (so only works with complete bypass)

Did I mention amazingly this flickering goes back through the splitter and affects all the other lights on the rig.

 

Plan to strip down the MH today and I suspect some kind of static on the DMX chip must be causing the problem, but never heard of interference on a unit with no power connected. Wierd.

 

I will keep you all posted of my findings. from memory the DMX chip in these is the DS 8.... something that is like an op amp, in that the DMX in an out are isolated, but with power off I think a relay bypasses the chip ....not sure.

[David Duffy]

Is this a real DMX splitter or just some cables bodged together?

 

You should have a terminator on the end of each and every line from the DMX splitter.

[boatman]

The first step is to terminate all the lines, including the line into the splitter. Then you can start looking for your problem. Also, get yourself one of these and it will pay for itself in time alone on the first job.

[tvi675]

Is the DMX splitter opto-isolated, and if so is it isolated on the input or the outputs? If it's only isolated on the input then anything dodgy on one of the outputs will spread across to the others. I'd echo what's been said about terminating all of the outputs and the thru from the input and see if this makes a difference.

 

Matt

[KevinE]

Please tell us what type of DMX splitter you're using.

 

Check that the DMX leads are proper leads and not microphone leads with earthed XLR xhells.

[boatman]

The OP did say that he had a Showtec splitter and described a setup using three outputs so I assume its the second one on this page. I don't know whether or not that model is opto-isolated, but I suspect the problem is down to either a damaged cable, or simply using microphone cable instead of DMX cable. However, until the OP comes back to give us more information, there's no more to say.

[Kazeja]

Have you tried connecting DMX in (source) to each output chain in turn? (i.e. bypass the splitter). Does each line behave itself?

 

Could be looking at PSU problems (caps) within the splitter depending on its age or useage.

[soundo26]

are you using proper DMX cable or mic cable?

 

Don't know that splitter but some have an output which changes the polarity, if yours has, don't use it with the others!