The Avolites Discussion Forum

So a big oops happened at my venue today. We got some new Leviton truss mount dimmers and I got the New Guy to cable them up. After he finished I turned on the Tiger Touch console to see how they work.
Well, they didn't work along with everything else in that universe. Output A was not outputting dmx at all. I was thinking the problem was in the desk so I tried output B, then C with the same result. No output.
Next I checked the cables. The New Guy Didn't use the dmx in/out, he used the Microplex in/out on the dimmers. When I plugged them in to the dmx in/out and used output D from the desk they worked fine.
Now I can't get any output from output A,B, or C. I reset the Nodes with no success.I pushed the panel reset switch, no success.
Does anyone know what else I can try?
Can anyone explain why microplex would "short out" the output of the desk?

Now I know Again......ALWAYS CHECK THE WORK OF THE NEW GUY!!!

I'd bet you fried the optos on the DMX boards, or the DMX drivers. Both are on sockets, so easily replacable. It's the white (8pin) and black (6pin) bugs located close to the DMX sockets in the desk. They're part of the spare kit, and usually you can even fetch them at some good electronics store. Shouldn't cost a fortune.

As you can see on the photo below, there are always two white chips assigned to each connector (MIDI, DMX1, DMX2). So, as a quick check, you might even swop the white chips between the MIDI section and one of the DMX connectors. Further, per connector there is one chip for output, and one for input. If you're lucky enough, only one direction got fried. Be aware that they need to be turned 180 deg when toggled between In and Out - you'll notice the printing on the board: 'U6' and 'U3' are reversed (and in my case, it seems U6 is inserted wrongly, thanks for asking...)


Click for larger version

Thanks for the reply. I finally found my spare kit and started to swap out items one at a time.
The bad item was the black 8 pin "bug" labeled U1. Only had 1 spare so I will order more. I am not an eletronics guy so what is thing called?
And what is it about the Microplex signal that fried the desk?
thanks again for the quick reply.

The "bug" as we are jokingly calling it is a microchip. in the case of the black one you replaced a DMX driver chip ( I can't remember the exact chip number off my head)

the reason they fried is that microplex sends voltage back thru the XLR to power the microplex board

you can also fry these chips by plugging in clear com to the desk .. ask me how I know ...... ( boy that was a bad day .. thank god for spares!!!! )

That's the xx75176, where xx is either DS (National Semiconductors) or SN (Texas Instruments). Of course, you need the DIP8 version.

Thanks guys. I disabled the Microplex on the dimmers so this will not happen again.
"The day you stop learning is the day you die"