DMX Cable Repair Woes

[GHSStageManager]

First, some background. The wall plug for my school's DMX line into the dimmers actually fell out of the wall years ago, so what we have started doing is to simply pick up the wall plug, place it near the board, and then connect the board to the plug. Lazy, yes. Irresponsible, yes - but it worked for the while it had to. Recently, the board no longer controls the lighting system - and what do you know, the red wire was disconnected from the wall plug and the black wire was on its way out.

So, thinking I found the problem, I set about to re-solder the data wires to the wall plug. Well, easier said than done. When testing the connections (with no input from the board), all I did was touch the red wire to its pin, and the lights would come to up to full. I would break the connection, and the lights would stay on for another second. Then, I made a quick physical connection with the red and black wires to their pins, and attempted to control the lights from the board. While the lights did come up, the board had absolutely no say on their intensity or the like.

What could this be? For reference, the board is a NSI MC 7524 with mostly ETC S4 jrs for fixtures.

Any help is greatly appreciated!

 

[epimetheus]

First, some background. The wall plug for my school's DMX line into the dimmers actually fell out of the wall years ago, so what we have started doing is to simply pick up the wall plug, place it near the board, and then connect the board to the plug. Lazy, yes. Irresponsible, yes - but it worked for the while it had to. Recently, the board no longer controls the lighting system - and what do you know, the red wire was disconnected from the wall plug and the black wire was on its way out.

So, thinking I found the problem, I set about to re-solder the data wires to the wall plug. Well, easier said than done. When testing the connections (with no input from the board), all I did was touch the red wire to its pin, and the lights would come to up to full. I would break the connection, and the lights would stay on for another second. Then, I made a quick physical connection with the red and black wires to their pins, and attempted to control the lights from the board. While the lights did come up, the board had absolutely no say on their intensity or the like.

What could this be? For reference, the board is a NSI MC 7524 with mostly ETC S4 jrs for fixtures.

Any help is greatly appreciated!

DMX or Microplex? Microplex has +15V of one of the pins for powering the board. The NSI microplex dimmer I had at my previous church would go to full with no input. This may not be a definitive test, but is the wall connector 3-pin XLR or 5-pin XLR?

Ninja Edit: What model are the dimmers?

 

[SHARYNF]

The NSI7500 series has both DMX out and MPX out, they are pretty clearly labeled on the back of the board, are you connecting to the DMX out (5 pin) or the 3 pin mpx out?

As asked by others what are you dimmers? do they give an indication of a signal?

Sharyn

 

[GHSStageManager]

That's a good question, actually. Because I am reasonably sure that we are using DMX here, but the board was set to use MDX before I began the repairs. The cable we are using is 5-pin XLR.

Dimmers are NSI 2408CD (three of them)

Edit - And also because the board needs to be plugged into the wall

Edit 2 - The only indication of a signal that I get is that they go to full on all channels

 

[SHARYNF]

The 2408Cd has a few oddities

http://www.allprosound.com/catalog/pdf/ownersman/NSI/2408op.pdf

These packs If I recall either go to the last setting which it holds for 10 minutes in case it looses DMX control OR goes to full on. If you then connect a dmx signal to it after the pack is up it then does a gradual fade back to the level the console is sending.

In addition, on the MPX side of things and I am NOT sure if this is also present on the DMX side IF there is a 0-10 volt signal present on the line that will override the console sent level

There are some leds' that Red shows power, Steady Green shows control signal and FLASHING GREEN shows it is executing a command on each channel there is a yellow led which indicates if that channel is active and also at what level


I am assuming that no one changed any of the internal setting on the dimmer, There is an option to send voltage over the DMX line (YES WITH DMX) but this uses 4th different wire.
Is it possible that you have missed one of the wires that is DMX that has broken off and that you are connecting a power wire up?


Standard DMX uses three wires but NSI in their infinite wisdom based on some of their consoles not having a power supply (NOT YOUR 7500) in their infinite wisdom ;-( decided to allow for power to be send on a 4th wire. This usually assumes that the common and this 4 th wire are 18 awg.

I'd check and see if you are getting any voltage FROM the dimmer pack on the connection without the console being connected.

I'd check to make sure that one of the 3 dmx wires is not connected and that perhaps you are connecting the 4 wire that supplies 15 volts thinking it is dmx

Because NSI 2408 uses Dmx/ MPx and Analog there are all sorts of oddities with these packs

Sharyn

 

[BillESC]

How old is your system? When was it installed?

 

[Studio]

Have you tried connecting directly to the dimmers (if possible) to be sure that it is that wall plate. I know some venues have more than 1 dmx input (wall plate) check FOH, the front of the stage, onstage, etc...
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[n1ist]

You may want to shut the system down (or unplug the cable from the dimmers) before soldering. Most soldering irons have grounded tips.
/mike

 

[GHSStageManager]

@n1ist - I always shut off the circuit breakers from the packs before soldering, if I need to do more, please let me know! =)

@Studio - The wall plug I am referring to is THE place in the auditorium to connect to.

@Bill - System is new within the decade, installed maybe 2005? No one is quite sure

I have been connecting Data + to pin 3 and Data - to pin 2, however I just noticed today that there is a short green wire (in addition to the shield, data + and data -) in the dmx cable from the wall. The green wire is too short and not stripped so it was obviously never used, but could that be a source of the trouble?

Thanks