DMX/Dimmer Problem

[JonM]

Hi.

 

I have recently bought a lighting setup and all is well apart from the Dimmers which don't seem to respond to DMX signals. No matter what channel I set the dimmer to use it just doesn't do anything. The dimmer itself must be ok because I can put it onto a 'random' mode and the lights flash and dim fine.

 

The desk I am using: Behringer Eurolight, LC2414

Dimmer: Soundlab G018VA

 

I have some LED lights which work fine in the same DMX system so I don't see how it could be cabling or controller and I have a terminator at the end.

 

Any suggestiong would be really appreaciated as this is driving me crazy.

 

p.s. I know this probably doesn't make much sence so let me know if I need to make anything clearer.

 

Jon

[3guk]

Quite possibly one of the pieces of equipment is using the reverse DMX standard.

 

Just swap pins 2 and 3 around in one end of the DMX cable and try using it that way, this problem all comes about because Chinese / Cheap manufacturers are not fans of following standards.....

[JonM]

Thanks, Will have a go and let you know how I get on.

 

Jon

[Andrew C]

If you do need to swap pins on the dimmers, don't forget to swap them back on the outputs; something like --

 

=====X= Dimmer=X======DMX LED=====DMX LED===Terminator

[maeterlinck]

Don't forget the unit itself could be faulty. No swapping of leads etc will fix that. Whoever supplied it to you should be able to offer some first line fault finding before you RMA it...

 

Edit: 'cause I can't spell...

[bruce]

That soundlab unit definitely has reversed DMX polarity.

Well, the one that I've got did...

[michael6388]

Mine also had reversed pins - shown on the pinout marked on the side panel. I fixed it by unplugging and turnung the jumper socket from the XLR connector to the PCB through 180 degrees.

[jfboss]

hi mate

its probs becuase you are using behringer ** laughs out loud **

a friend of mine once used that desk and he couldnt get the DMX to register eather

whatever he tryed he couldnt get it working he just gave up and got a propa desk ** laughs out loud **

x

 

Moderation: Quality Control: The quality of this post falls well below the standards expected on the Blue Room. There is no punctuation, no capital letters, and 7 "typos". On top of that, the Behringer desk can be made to work without trouble if used properly. See topics all over the place on the need for useful and intelligable posts.

[matt c]

hi mate

its probs becuase you are using behringer ** laughs out loud ** :** laughs out loud **:

a friend of mine once used that desk and he couldnt get the DMX to register eather

whatever he tryed he couldnt get it working he just gave up and got a propa desk ** laughs out loud **

x

 

As others have said, it sounds more like your comms polarity is inverted on the dimmer.

 

I don't know much about DMX, but it is based on RS485, which is in my field of work. Oh the joy of educating service technicians not to use a voltmeter on the A and B lines to determine whether the system is faulty.

 

Some of these equipment manufactuers really should take the time to conform to standards. It just makes them look silly.

 

Matt

[JonM]

I resoldered a couple of cables the other way around and it works fine now. Is there a way of changing something inside the dimmer itself? I don't fancy opening it to look in case I void warantee.

 

Thanks

 

Jon

 

p.s. No problems with the desk itself. Perfectly happy with it so far.

[matt c]

If the XLRs on the dimmer are not directly mounted onto the PCB, you could switch the wires inside, just as you have done for the cables. Usual rules (switch off and unplug, wear an anti-static wrist strap, if you're not sure, don't etc..) apply.

 

If they are directly mounted, you could make up a couple of short crossover leads, and fix them to the dimmer with a cable tie or some such.

 

If you're lucky, you may find that there is a connector between the XLR jack and the PCB, which will flip around, and make the polarity correct.

 

Matt

[bruce]

we've been here before - do a search.

 

The XLRs are directly soldered to the PCB - at least, they are on the ones that I own. However, if you follow the tracks, you'll find that the 2 XLRs are directly connected together, as expected, and the + and - lines are connected to the rest of the circuitry by 2 resistors. these are actually "crossed over", even though the screen printing on the PCBs suggest that they should be "straight across".

 

Simple job to fix - just resolder 2 resistors, though you have to dismantle the whole thing to get at the solder side of the PCB. And it'll invalidate any warranty.

 

It looks to me like they have actually designed the PCB correctly, but screwed up the printing on the outside of the box, and have decided it's cheaper and easier to change the electronics rather than re-do the artwork!

[JonM]

Ok, thanks for everyones help. I opened it up and found there were wires attached to the DMX sockets and managed to unsolder then resolder them back the 'correct' way and everything works perfectly now.

 

Jon