Control/Dimming Pulses and flickers in High School Theatre lighting

ARGH! I've been reading posts for a few hours trying to logic myself through this a little more. So I am the 'volunteer tech guy' for a local high school, having majored in production in college. This is very handy, since the theatre has 90s era equipment I am familiar with.

This is a large high school, and they spent a fair amount of money when it was new in the 90s. They have power conditioning, ETC dimmer racks, and a ETC Impression with a remote stage manager override. I can get specific model numbers if it would be helpful.

There have been a few isolated moments in the last year - lights will dim for 1/10 of a second, or just randomly pulse a little (like from 95% - 100%). When this happens, they ALL pulse. It is usually over in seconds, and we are left scratching out heads. The kids explain it as the resident theatre ghost, and I'm half tempted to go with that.

Lately seems to be getting worse, to the point we can actually interact with it while it is acting weird. Turning the main board off and using the stage manager console has no effect, and I have looked at the level for that channel on the dimmer rack control panel, and the level stays constant while it is freaking out. Based on those 2 bits of info, I feel comfortable ruling out the board and DMX to the racks. (tell me if I am wrong here)

I also watched the power conditioning readouts during a episode. I can see nothing on their - voltage may very 5 volts, but very slowly over minutes, nothing like the flicker. I also noticed the AC equipment was not on when this was happening - luckily the dimmer room is right past the AC room.

What is my next step? At this point, I am the expert there - they didn't even know they had dimmer racks when I started helping out. I want to help lead them to help, but I don't even know what direction to go.

Thank you all for your wisdom!

-RJ

Uncle Dirtnap said:

ARGH! I've been reading posts for a few hours trying to logic myself through this a little more. So I am the 'volunteer tech guy' for a local high school, having majored in production in college. This is very handy, since the theatre has 90s era equipment I am familiar with.

This is a large high school, and they spent a fair amount of money when it was new in the 90s. They have power conditioning, ETC dimmer racks, and a ETC Impression with a remote stage manager override. I can get specific model numbers if it would be helpful.

There have been a few isolated moments in the last year - lights will dim for 1/10 of a second, or just randomly pulse a little (like from 95% - 100%). When this happens, they ALL pulse. It is usually over in seconds, and we are left scratching out heads. The kids explain it as the resident theatre ghost, and I'm half tempted to go with that.

Lately seems to be getting worse, to the point we can actually interact with it while it is acting weird. Turning the main board off and using the stage manager console has no effect, and I have looked at the level for that channel on the dimmer rack control panel, and the level stays constant while it is freaking out. Based on those 2 bits of info, I feel comfortable ruling out the board and DMX to the racks. (tell me if I am wrong here)

I also watched the power conditioning readouts during a episode. I can see nothing on their - voltage may very 5 volts, but very slowly over minutes, nothing like the flicker. I also noticed the AC equipment was not on when this was happening - luckily the dimmer room is right past the AC room.

What is my next step? At this point, I am the expert there - they didn't even know they had dimmer racks when I started helping out. I want to help lead them to help, but I don't even know what direction to go.

Thank you all for your wisdom!

-RJ

Click to expand...

@Uncle Dirtnap Hello! By any chance, does your school use an IBM, Simplex, Stromberg or similar system which pulses approximately one or two KHz tones on your power lines to operate synchronized bells to signify class change times along with warnings thereof? We had a system which was city wide that coordinated all bells, including for night school and weekend courses, in the private school board in Hamilton, Ontario, Canada. One time I was involved with an amateur production using 10 Kodak Carousel projectors operating across three screens using three separate dissolve sytems; two x two-way Spindler Sauppe and two x three way AVL Coyotes. Our projection would all work flawlessly EXCEPT when the school board's bell system would wind up its motor / generator and use a relay and capacitor bank to superimpose pulses on the school's power. Up here in Canada, we commonly jump from 3 phase 5 wire 120 / 208 VAC to 347 / 600 VAC where the U.S. more commonly jumps from 120 / 208 to 277 / 480 VAC. The Simplex system in Hamilton was using a 3 phase 120 / 208 motor to spin a 347 / 600 VAC generator putting out something like 1.6 KHZ through a pulsating contactor through a bank of capacitors on to the secondary of a 3 phase transformer driving every Simplex clock and bell in the school. We had to get "SPECIAL PERMISSION" to have a custodian unlock a breaker panel for us prior to performances where we were allowed to leave the motor's breaker on so the system wouldn't report a motor failure BUT switch off the 3 pole breaker which fed the output of the 1,600 Hz generator to our local panel powering the theater and music classroom wing of the school. After every performance we had to flag down a custodian again and switch the 3 pole breaker back on. This way none of the remainder of the school was effected with night school bells ringing throughout the school per normal but with no bells and ten happy projectors in the theatre. The next time we rented the auditorium, we built our own 1.6 KHz filter to notch the tones from wall receptacles in the booth. This is somewhat of a variation on what used to be termed "carrier current" broadcasting and was popular for campus wide student broadcasting stations on university and community college campuses. We even had a technical high school in Hamilton with their own carrier current high school radio station in the 1950's. Perhaps @FMEng would care to comment?
I'm NOT saying this is your problem, merely mentioning it as a possibility.
Toodleoo!
Ron Hebbard.

Since it is an ETC system, give them a call when you can be there. They very likely have the system design documents at hand for the installed system.
One other thing, you say they didn't even know they had a dimmer rack, have they ever done any routine maintenance. I'm thinking of cleaning the filters and such. ETC can also help you with routine, SAFE procedures to use (LOTO and such).

My quick diagnosis is the rack is going into thermal protection due to low air flow.

Best solution is to call ETC. When you buy their systems, you pay for their tech support. Please use it as it is easy and very helpful to diagnose issues. On their web page they have lots of useful info. Here is a page from their site dealing with sensor dimmers flickering. https://www.etcconnect.com/Support/Articles/Sensor-Flickering.aspx
For technical support in the Americas,
please call 608-831-4116
or toll-free in the U.S. at 800-688-4116
[email protected]

Other possible problems I have seen:
A bad CM module in the rack. The rack may be 20-25 years old and the control module could be failing. This will require contacting ETC, your dealer, or local company to get a loaner.
Clogged filters. Follow the instructions for safe cleaning the rack. See if the solves the issue.
The control console could be failing as it is getting old. Try a substitute console and see if the problem persists.
See if you can run a secondary DMX line from the console to the rack and see if you got a bad cable working in the system.

I had a similar problem back when I worked in a theatre with the same vintage ETC Sensor racks. It turned out it was an airflow/overheating problem for the dimmer rack's controller. The solution was replacing the air filters.

I would recommend a visit by an ETC service tech, which is what fixed our problem. We pointed a box fan at the controller before we could get a tech out to stay open, but that's obviously a bit of a hack. I wouldn't do that again without asking ETC...

You folka are fantastic! We are right in the last 2 nights of a show, so it will be a week or 2 before I can update everyone. Thanks again for your help-

-rj

I might suggest two things -
1- clean the racks and filters.. could be an airflow issue.
2- our of curiosity, have they added moving lights or LED’s to their rig ? If so.. how are they getting DMX to those devices, and how are they managing the power to them.

I see a lot of schools buying LED’s and not installing data and power per the standards for each.

More system info please

We have had similar issues with our lights dimming to black and back to full repeatedly on their own (ETC Express 48/96, ETC Sensor dimmer rack). ETC tech support was a big help. We ended up having to disconnect all of our wall button stations to reboot them. That fixed the problem. It has reoccurred twice since last summer but luckily on dark days. Good luck.

Update: I took some responsible students and tackled it last weekend. We killed the power and vacummed and blew out a disturbing amount of dust. (probably 2 cubic feet of dust bunnies in the corner of the room we used to do the work, no lie. Since then, no problems at all. Victory! I'm need to come up with a maintenance and procedures manual.

Something I forgot to mention - when I first got involved years ago, I noticed that someone had spiked the master fader to 80%. No one knew why - it just 'didn't work on full'. After talking to some former students, it had been that way for at least 8 years. Before the great cleaning, it would make the flicker problem crazy - goes back to heat issues, I'm sure. We are back at full, and these poor kids are seeing their lights on full for the first time ever. The poor lighting kids are having to rethink all their gel choices, but it's for the best.

As always, thank you all!
-rj