Yeah, google
arc-flash and that'll be an education.
Is the
CEM throwing any errors? I've gone through the wars with our racks on a few different types of
CEM faults and on occasion you'll get one that only displays intermittently when the fault is actually occurring. I also
plug the
ETC helpline, I spent many, many hours on the phone with them in this past year and those guys working the helpdesk are total rockstars.
The first thing you really should do is some tear-down troubleshooting. Eliminate everything from your
system except the
console and the rack. Try a difference
console, if it still flickers then it's probably not your
console doing it. Try and find what actually correlates with the flickers to isolate it to a specific component by eliminating everything and adding or replacing one piece at a time. Once you replicate the correct circumstances for the failure to occur, you'll have a good idea of what is causing it.
ETC's helpdesk will walk you through this too!
One thing I've found that's a common failure in lightning heavy areas is the failure of a 75176 transceiver chips. This is the little guy that takes your
DMX data and turns it into the RS-485 compatible differential signal. It's also the first thing in the box that the lightning/static/
ESD tends to zap since it's pretty much the last component before you hit the
DMX cabling. Fortunately, those crazy, wonderful kids at
ETC made this a socketed chip so it's pretty easy to swap.
You have two in your
CEM toward the back, and you also will have two optocouplers (6N137), one for each
DMX input into the
CEM (see the pic). The optos can also get zapped. If you check one of the electronic component supply houses you'll find these for pretty cheap, I picked up a tube of them for less than $10 last time. There's a few different models of the 75176, so your best bet is to just take the whole number off the chip and google it. Check the spec sheet to make sure the pinout is the same and you should be good to go.
In anything connected to your
DMX line there will be some flavor of RS-485 transceiver and usually an optocoupler (including optosplitters!).
ETC likes the TI ones, but there's also a MAXIM version that is virtually identical, but more expensive I think. I'd check your arch controller as well and your
console if swapping these chips don't make much difference.
That all said,
DMX is pretty funky and the RS-485 standard is very robust, but prone to EM interference when not properly installed. I'd go through your
system with a fine-toothed comb. Check
polarity on cabling, check terminations. I threw out the chip replacement since I've had that happen a few times after bad storms and it often fixes bugs here and it's a cheap and easy swap, but we still don't really know what part of your
system is getting the errant data.
@StradivariusBone An excellent read you wrote Sir and, in
return, a dumb little tale of
ESD.
Some decades ago, I'd gone with an
amateur group to spend a long day in a province wide competitive
theatre festival here in Canada. The host group had an
Express, driving a
Unison driving a Sensor rack plus a collection of analogue zero to ten
house and
lobby light dimmers controlled by wall mounted architectural stations in at least three locations. The competing group I was visiting with were carrying their own
Strand MX48. Their
Strand board had all of their LXQ's in it and normally outputted AMX-192 to their dimmers but would readily put out
DMX 512 in this competitive festival situation. The host group's board was in a decent booth at the rear of the balcony and spoke
DMX via a short 5 contact cable into a wall mounted 5 contact input to the
Unison located in the basement below the
stage and adjacent to the Sensor
stage lighting rack. The visiting group who'd competed the previous day / night had used the host's
Express and everything was functioning normally. The group I was visiting with began their day with their MX48 on a production table on the lower
level for the mutual convenience of the director, LD, SM and board op'. They were also travelling with all aspects of their own sound, task lamps and intercom and had no trouble lashing everyone together for an early afternoon tech, followed by a full run for everyone's benefit. The visiting group had routed their own 100'
DMX cable from the booth's
DMX input, out the window, through the balcony, over the
rail and down to their MX48. The host group's technicians had been asked to please remove their
Express from the booth counter over the course of the day so the competing group could place their MX48 in its place during the dinner
break in preparation for the evening's competitive performance with sold out audience.
So far, so good. "Peachy keen!" Everything's going swimmingly.
The set went up in the morning and a
minion ran the MX48's sliders for focusing and then everyone broke for lunch.
After lunch the tech' ran smoothly followed by a full run through with LXQ's being quietly / seamlessly touched up / down on the fly with nary a disruption.
The happy director, cast and SM broke for dinner with the LX and sound crew expecting to join them shortly.
You can probably see this coming.
It didn't happen quite like that.
I'll boringly plod through this step by step.
The sound crew struck their ClearCom and relocated it to the booth and both sides of the
stage.
The LX crew took their MX48 up to the booth and set it up in the host's booth.
The MX48's
DMX512 output was plugged into the host's wall mounted input
receptacle with the host's 15'
DMX cable and the MX48 which had just worked flawlessly all morning and afternoon no longer worked. It looked like it was working but nary a
stage light was responding.
Huh? What the heck? What's going on?
Maybe the host's 15'
DMX cable which had worked the previous day had suddenly failed? Nope!
The host's techs tested their cable with their
Express and now that wouldn't work either.
Downstairs, the
lobby was filling up with anxious patrons.
Upstairs in the booth, fingers were being pointed and tempers flaring.
O.K. Step by step.
The day / night before all of the host's systems had functioned perfectly.
The visiting group had run a 100'
DMX cable,
DMX not mic cable, to the
main floor and all had worked.
The 100' cable was struck and the visiting group's MX48 relocated to the booth and things were no longer talking.
A check with a Goddard Mini
DMX'ter revealed the following.
Both boards', the
Express and the MX, were spitting out workable
DMX.
The host group's 15' five contact cable was functioning on contacts one through three as expected, no problem.
Sending
DMX from the Mini
DMX'ter produced nary a glimmer from the
Unison / Sensor combination. The wall stations controlling the
house and
lobby lights were still functioning normally.
The host
theatre's manager phoned his 'hot
line number' and Chris Mentis [Who was then commisioning and servicing ETC systems across all of eastern Canada responded.] Chris wisely recommended powering down and re-booting the
Unison but the
theatre's manager refused to do it as he had a
lobby and bar full of happy patron's sucking back their favorite beverages.
Next step, the Mini
DMX'ter went to the basement
dimmer room, bypassed the
Unison by unplugging one of its outputs and connecting directly into the Sensor rack which woke up immediately wondering why the work lights were on in the normally dark
dimmer room.
Next the MX48 and the 100'
DMX cable were rushed from the booth to a dark USR corner and the cable routed downstairs to the Sensor rack. LX organized
power for the MX and a task lamp for the board op'. Sound organized ClearCom for the
theatre manager who agreed to operate houselights from a DSR location and a
headset for the board op'. A relieved ASM organized an icy cold (non alcoholic) beverage for the LX board op'. Doors were opened and gleeful patrons were allowed to enter only moments past the half.
After the performance, and public adjudication, once the
house and
lobby had cleared. The
venue manager agreed to reboot the
Unison to ascertain the situation for the next day's group. The
Unison was happy upon its reboot and life went on with tempers somewhat frayed.
Here's my best guess as to where it all went wrong due to the eager impatience of an overly eager willing helpful
hand.
Had I struck the 100'
DMX cable from the
main floor myself, I'd have first unplugged it from the
Unison's input PRIOR to dragging it across the lower
level's carpeted aisle and neatly over and undering it in the booth. The overly eager willing helpful
hand chose to wrap the 100' cable as he would've his garden hose leaving it still connected to his garden tap. I strongly suspect dragging the cable's
jacket the length of the lower
level's dry carpet generated enough static electricity to totally confuse the poor
Unison. It probably was scared enough in its dark room in the basement without someone giving its input the 'cattle fence' treatment.
That's my best suspicion and I'm standing by it.
To this day, I've never regretted purchasing my Goddard Mini
DMX'tr. At the time, Mr. Goddard was the only one marketing such a product.
Toodleoo!
Ron Hebbard.