DMX Signal Problems


I have a Zero 88 BetaPack with built in DMX controller, and a Horizon 24 Channel hard wired dimmer rack, again with a built in DMX controller, but with a different connector.

I have managed to connect a standard 5 pin XLR connecter to the Horizon so that I can use it with the BetaPack and have control of all 30 channels from one desk.

Currently I have my Strand MX desk, which has been tested on a fully working rig and works faultlessly, and a cheapo lighting desk at the school where the Horizon is.

Now for the problem.....

When I plug in the cheapo desk into the Horizon and run a cable to the BetaPack I get a signal all the way down, and can control the lights on the BetaPack if I set the start address to under 24. This is fine, and works, but the desk is not software patchable and does not include any effects programming features, (which would be useful as I am running a dance show).

However, if I plug the MX into the same line, all goes downhill and the signal drops.

If the MX is plugged straight into the BetaPack though, lo and behold the betapack works, but as soon as the cable between the BetaPack and the Horizon is plugged in the signal is dropped.

Also if the MX is plugged straight into the Horizon, there is no signal to the Horizon board. :?

If anyone has any bizarre, random or even sensible ideas on how to make it work it would be most appreciated, as I havent got enough hands to control two desks at once so that I have control of both desks!!!
Check the pinouts for each stage. Make sure the DMX Pinouts for the Cheapo board output, and Horizon dimmer input, Strand Mx output, are all the same. If the horizon dimmer has a terminator have you removed it. There should only be one terminator in the line. Is the beta pack 's terminator connected.

If you connect the Beta pack to the cheapo board then to the Horizon Pack do they all still work?. If not then you probably have crossed wires in the Horizon pack. Just a thought.
Have checked all of the outputs from all of the bits of equipment and they all work fine. Have only placed one terminator in the line at any one time, as I only have one terminator to plug in.

Unfortunatley I have found out today that the resistor has died :-( in my terminator. Just going to find another resistor and all should work fine.

Will post back soon wil the results, thanks for the advice cutlunch.
Further to my last post, I have been, made and tested a new terminator, but unfortunately to no avail. Back to square one if anyone else has any ideas.

I have managed to test both of the lighting desks on another fully working system and have found that they both work flawlessly.

Haven't yet been able to test the Betapack with another system but that should come sometime early this week.

What else might be the problem with the setup?
Can you post the links to the manual for the Horizon Pack, including the DMX interface, and El Cheapo board here.

Something else to look at is, the cables you are using . Make sure that the cables do not have the metal cases connected to ground - pin 1 at the ends. This can cause ground loops which may cause problems. You could even try disconnecting pin 1 from one of the cables when connecting the MX only to the Horizon dimmer.

Also what version of DMX512 is the Horizon running? Sometimes there can be timing conflicts between different standards. The MX is running DMX512 (1990).

You may have a DMX tester but if you don't, the link below shows you a simple one made from a XLR , two resistors, a Bi-LED. By following the test instructions you could use it to see, if when the MX is plugged into the Horizon dimmer, if a short circuit is being created. NB the tester acts as a terminator so you don't need your other one. I would even do a test with the MX and the horizon where you don't use a terminator and see what happens.

I don't know how your cables are wired but if your are using Pins 4 &5, disconnect them. I hope this gives you some ideas.
I have yet to find a website or manual for the Horizon rack or the cheapo board on the Internet. It seems to be a standard fit rack and board for schools but I think that the company has gone bust.

However, when I have done the same thing with other Horizon boards in other schools in the local area all has worked fine.

I'm beginning to think that after 20 years in service this Horizon rack may finally be heading for the scrapheap.....

I will try disconnecting the ground off the cables and see what happens then. Unfortunately again, I am having to use two cables, as the old cheap board uses pins 4 and 5 to recieve 20V+ and - from the Horizon Rack.

No short circuit is being created between the Horizon and the MX. Have tested this. Was quite amazing taking out the trips for the entire building for the school, as the load was a bit high when DMX+ and DMX- crossed and turned everything on.

Not sure about the timings between the different devices. May be something to look into.

P.S Thanks for the link about the DMX Tester. I can build one of my own now instead of stealing my mates every other week!!

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