Flickering Lights on ETC L-86

[LesWilson]

Everything has been fine since we renovated our venue last March. Out of the blue, specific dimmer circuits flickered when used. Others flickered even when not used. Hours later, everything would be fine. Been chasing this for a week. I read this 10 year old CB thread: https://www.controlbooth.com/threads/flickering-fluttering-lights.6422/#post-72085

In my case the 18 flickering circuits are all in Bank 3 of the 96 channel rack. All of the EM64 control module jumpers are set to 1 so the statements about each one being set for different addresses is confusing. The EM64 manual indicates values of 1, 49 or 97. Our unit is 96 channels in 3 banks. [Head scratching here]

Swapping a dimmer tray with a non-flickering circuit in another bank did not resolve the problem. Swapping in a spare controller did not resolve the problem. The 3 legs metered at 118v, 120v and 120v but at the time it was metered, the problem was not manifesting itself. We're running out of ideas of what to try next to isolate the problem.

Could this be a power problem? Interference from something else? What am I getting wrong with the EM64 addressing?

TIA

 

[RonHebbard]

Everything has been fine since we renovated our venue last March. Out of the blue, specific dimmer circuits flickered when used. Others flickered even when not used. Hours later, everything would be fine. Been chasing this for a week. I read this 10 year old CB thread: https://www.controlbooth.com/threads/flickering-fluttering-lights.6422/#post-72085

In my case the 18 flickering circuits are all in Bank 3 of the 96 channel rack. All of the EM64 control module jumpers are set to 1 so the statements about each one being set for different addresses is confusing. The EM64 manual indicates values of 1, 49 or 97. Our unit is 96 channels in 3 banks. [Head scratching here]

Swapping a dimmer tray with a non-flickering circuit in another bank did not resolve the problem. Swapping in a spare controller did not resolve the problem. The 3 legs metered at 118v, 120v and 120v but at the time it was metered, the problem was not manifesting itself. We're running out of ideas of what to try next to isolate the problem.

Could this be a power problem? Interference from something else? What am I getting wrong with the EM64 addressing?

TIA

View attachment 17460

@LesWilson Are there any heavy loads, such as decent sized Variable Frequency Speed Drives for Cyclovac's and / or air handlers, possibly spewing harmonics intermittently onto your venue's incoming power?
As for addressing; I'm far too tired to make sense of a rack I'm not familiar with at the moment. Scoping the incoming power would be useful even if only a dual trace oscilloscope is the best you can muster.
Toodleoo!
Ron Hebbard

 

[JonCarter]

Don't know how power to your "banks" is supplied, but can you get to the feeders to the banks or buss bars feeding the banks? If so, get out your IR camaera & look at supply connections. Anything hot? In particular, anything on the suspect bank warmer than anything else? Maybe just shut down the power to the board and re-torque all the supply connections and buss bars -- everything on that bank.

 

[Mac Hosehead]

I have seen problems with the opto-isolation module, LMI-EMI3M, cause flickering on the dimmer output. This module splits and isolates the DMX input to the three banks. A failing capacitor can cause the problem to come and go. There is a way to bypass the module but it also defeats the isolation. I think a call to ETC tech support would be worthwhile in this situation.

 

[LesWilson]

Thanks for the fast response. The good news is that it's contained to one bank. I'll be onsite for a couple hours today and hopefully it will happen and I can do more PD. In the chance it's a bad power cube (SSR), I'm going to flip breakers on flickering circuits until it stops or pull trays to see if one or more might be the culprit.

 

[derekleffew]

...I'm going to flip breakers on flickering circuits until it stops or pull trays to see if one or more might be the culprit.

Call Tech Services at 1-800-688-4116 while at the rack before doing anything. Before pulling trays, you must either LOTO the rack, or wear appropriate PPE.

All fans running and filters clean?

 

[LesWilson]

Flipping breakers and pulling trays had no effect other than to stop the flickering on those circuits. I removed all trays with malfunctioning circuits. I could insert any given tray and the bad circuit(s) would flicker. Our TD says to call ETC.

 

[starksk]

I second your TD's suggestion to call us at 800-688-4116 when you can power off the rack. Based on the symptoms that you've described and having swapped dimming modules and control modules and the issue staying in the same column, I'd say that it is more likely the issue is with the I3M module.
This description is spot on:

I have seen problems with the opto-isolation module, LMI-EMI3M, cause flickering on the dimmer output. This module splits and isolates the DMX input to the three banks. A failing capacitor can cause the problem to come and go. There is a way to bypass the module but it also defeats the isolation. I think a call to ETC tech support would be worthwhile in this situation.

 

[Ancient Engineer]

Or... plausibly you have a wonky DMX data path/termination/DA/signal weirdness.

I had a flickery set of dimmers and discovered that somebody had generously replaced a DMX cable for us with a tragically miswired (how'd that happen??) mic cable..

Swap-a-voused the cable and it returned to happiness, well... maybe contentment.

Just a 'nuther thing to try...

 

[LesWilson]

EPILOG: ETC support is fantastic. They suggested swapping the I3M module with a backup. I did the swap and ran the lights for two hours with no problems. Support indicated there's a capacitor for each bank and one capacitor could be in the beginning stages of failing. I couldn't see one that looked swollen or discolored but... anyway, that was it.

 

[FMEng]

Capacitors don't swell all that often, and they don't discolor. It's almost always the electrolytics that fail, and those located near heatsinks and voltage regulators are frequently the culprits. For just a few $ and 30 minutes of time, replace C1, C3, C5, and C7. Be sure to note the polarity before removing the dead ones. Chances are good that you'll have a working, spare board to have at the ready again.

 

[LesWilson]

I have decent soldering skills. The board looks straight forward with surface mounted capacitors. Easily replaced. I might just do that.

 

[Ancient Engineer]

One of my favorite cap-splosions... This is almost exactly how it looked when I extracted it from some Crown amp or other... I soldered it to a fender washer for a mini-trophy...

We vaporized (really) some very large caps in crossovers in 300W-RMS subwoofers that accidentally got 4000W-RMS for a few hours. The technician in-question thought that we had "mistakenly turned down those amplifiers"...

 

[FMEng]

Electrolytics are good at exploding if they get installed with the polarity reversed, or if the voltage applied far exceeds their rating. I've never seen one explode that was adequately rated for the application and installed correctly.

 

[LesWilson]

Well, 8 months later, the spare started exhibited a flicker problem in one bank so I bit the bullet, got some caps from mouser.com and replaced all 4 caps in the module that went bad back in February. The repair resolved the problem. This is the part I used: 710-860160474017
Here's the datasheet: https://www.mouser.com/datasheet/2/445/860160474017-1078637.pdf