Urgent DMX Help!

[Vin Trouble]

Hi everyone, Newbie here needing your expertise please! I've been using a program called Alien Apparatus to run my backing tracks, MIDI, DMX and lyrics for live performance. Lights wise I have used an LEDJ DMX backdrop and a pair of generic 36x1Watt LED cans up until recently, when I sold the cans and purchased a single LEDJ Slimline 9Q8. The problem I have is really freaking me out, and is probably very dangerous too! When I'm running my editing software with the backdrop controller and 9Q8 DMX'd together (in any order), when I raise the velocity for any of the 4 colours on the 9Q8 smoke starts to come out of the backdrop controller! I have two of these controllers, and two of the backdrops - same result - I opened up the controller, and there is a resistor that glows orange when this happens, melting the PCB in the process! This stops when I pull back the velocity fader. When used in isolation, no problem. Please help me!

Best wishes, Vin.

[musht]

As far as can gather its the power supply for the LED startcloth thats doing the unitended smoke machine impression?

 

What size is the backdrop as a matter if interest, seems to be a variety of sizes?

 

Smoke would seem to indicate PSU unsable to supply enough current to power all the LEDs at once.

 

The controller should suppress that trying to happen but for some reason dosnet appear to, have you tried the backdrop on its own and been able to replicate the symptom?

 

EDIT sorry just saw in isolation no problem...

 

Velocity is a midi term what effect is intended to have on the DMX channels?

[timmeh2]

Hi

 

Dare I say that the 9Q8 is broken? Meter out the DMX line voltage by measuring across pins 2 and 3. Anything more than +5v and you've got a problem.

 

All the best

Timmeh

[Vin Trouble]

Hi musht cheers for replying. It's a 3m x 2m backdrop. Worked fine in conjunction with my old 36 x 1W pars. Velocity - sorry I mean brightness - pushing up the faders for the 9Q8's RGBW colours results in meltdown on the controller for the backdrop. I'm thinking a voltage is coming from the 9Q8 and frying the backdrop controller? It must be the 9Q8, as previously no problem? Each in isolation works fine.

 

 

[musht]

Going with Tim, sounds as if something nasty coming from 9Q8 but usually just expect DMX I/O to be paralelled so would affect controller as well.

[timmeh2]

Going with Tim, sounds as if something nasty coming from 9Q8 but usually just expect DMX I/O to be paralelled so would affect controller as well.

 

Usually true, although I'd expect the controller be fully opto-isolated whereas the starcloth boxes will be anything but.

[Vin Trouble]

Hi Timmeh, Thanks for replying. At idle ie all faders down, I'm reading 0.33 at the 20(V) setting on my multimeter. This is with the red +ve probe in pin 2, and black in pin 3. Is this about right? The manual says pin 2 is cold and pin 3 is hot. It's been around 20 years since college!

[timmeh2]

Hi Timmeh, Thanks for replying. At idle ie all faders down, I'm reading 0.33 at the 20(V) setting on my multimeter. This is with the red +ve probe in pin 2, and black in pin 3. Is this about right? The manual says pin 2 is cold and pin 3 is hot. It's been around 20 years since college!

 

Hi Vin

 

Disconnect your starcloths and put on of the faders up. What reading do you get now?

 

All the best

Tim

[Vin Trouble]

Hi Tim,

Crazy stuff.

Idle 0.33

Red @ 255 0.27

In fact, this is the score for any colour in isolation.

2 colours 0.19

3 colours 0.12

 

Sounds like polarity's wrong, so:

Red to pin 3, black to pin 2 and:

Idle - 0.33

one colour -0.27 etc......

[KevinE]

Are you sure everything is set to slave mode in the DMX mode? I wonder if there is a data clash on the DMX line that is causing excessive current in the DMX tranceiver circuits. LEDJ stuff (being disco grade, generally) is often meant to work master-slave only with other LEDJ stuff and without a seperate overall DMX controller. Maybe the Starcloth controller is trying to act as master and generating DMX that is conflicting with something else. The resistor might be a supply buffer for the tranceiver that is having a hard time trying to stop the chips from blowing.

[Vin Trouble]

KevinE thanks for replying. Excessive current is a big possibility - I'm still eyeing the 9Q8 suspiciously as he was the last guy to arrive, and everything was fine before. I should also mention that the original semi-fried backdrop controller works on it's own DMX'd, but if I stick the 9Q8 in the circuit the backdrop no longer responds to DMX, although the 9Q8 does. This applies when using either fixture either first or second in the chain.

 

 

[DrV]

I think you have a short between either the output of the backdrop controller and ground or the output of the LED drivers and ground (I mean the actual power output which drives the LEDs etc, not the DMX output if it has one). When you increase the output it tries to push logic ground below frame ground. If these are tied together you get the excessive current. To find out where the fault is connect up each unit separately and put your meter between a DMX pin and mains earth. You should get a small voltage, certainly less than 5v. Then as you increase the level you should see the voltage increase to something large (whatever the internal drive voltage of the unit is). You can do this on each unit in isolation so that you don't start any fires! The real clincher will be that you will see the DMX voltage go negative with respect to earth.

 

It's a lot easier with a scope but you should see it with a meter.

 

Hope this helps

Dave

[Vin Trouble]

Hi Dave, I'll have a go at that shortly - a bit ubove my grade, but your excellent explaination should talk me through. Just to reiterate, I've 2 backdrop controllers, identical, and they've both fried, so logic would dictate the problem emanates from the 9Q8, so hopefully I'll find the fault there.

I think you have a short between either the output of the backdrop controller and ground or the output of the LED drivers and ground (I mean the actual power output which drives the LEDs etc, not the DMX output if it has one). When you increase the output it tries to push logic ground below frame ground. If these are tied together you get the excessive current. To find out where the fault is connect up each unit separately and put your meter between a DMX pin and mains earth. You should get a small voltage, certainly less than 5v. Then as you increase the level you should see the voltage increase to something large (whatever the internal drive voltage of the unit is). You can do this on each unit in isolation so that you don't start any fires! The real clincher will be that you will see the DMX voltage go negative with respect to earth.

 

It's a lot easier with a scope but you should see it with a meter.

 

Hope this helps

Dave

[Vin Trouble]

Just a wee update. I returned the 9Q8 and on receiving a replacement tried that with the backdrops - same result! Tested with both a laptop and PC. Not sure what's next - anyone near the West End in Glasgow able to let me try these lights with your lighting controller? Will pay you for your time.

[pmiller056]

Sounds like something is seriously faulty. Any quick 'n' dirty bodge repairs in the past to any equipment? Are the power

leads correctly wired? When did you last have your kit PAT tested? A proper PAT test will point to the faulty equipment

very quickly. Ask the person doing the testing to make a point of checking that all DMX connectors are not hazardous.

 

Past experience is that it's the older equipment in use (particularly if it has been on the road) that is causing problems.

Just because it is working correctly does not mean that it is safe to use. The signal specs for DMX512/RS485 take

account of inadvertent signal shorts/opens and they will not cause a hazard if everything connected is operating

correctly.

 

Regards, Peter