Flickering Lights

Chaos is Born

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Jun 30, 2006
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Cincinnati, Oh
Ok, So this has been puzzling me for some time now. Our house lights in one section of one of our dimmer racks are flickering every so often. Up until today i thought it was caused by humidity. But today when they flickered i went up to the Racks and there was a RH of 30%, Usually the flickering hadn't happend till twice that amount.

What else could cause flickering in a set of dimmers, Dims and Non-Dims alike?

There are 4 of them in a T pattern in the Rack, the three on one level and the center one on the level below them.
 

jmabray

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Ummm, I have never seen humidity cause flickering. Not saying that it can't - I just have never seen it.

We need some more information before we can help. What rack is it? Can you describe more about this "T" Pattern?
 

avkid

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Ummm, I have never seen humidity cause flickering. Not saying that it can't - I just have never seen it.
It rains inside our building when it rains outside.(through a pipe into a trash can now)
I have never seen that happen either.
 

JD

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North Wales PA
Need a lot of more information!
How many dimmer units are involved?
If more than 1, do they flicker in sync with each other?
Is it an analog or digital control system?
Flickering can be caused by anything from a loose lug in a power distribution panel (bad) to a bad capacitor in a dimmer's ramp generator. On analog systems, noise can occur in the control snake if there is moisture inside. On digital systems, the dimmer interface module could be going bad. Generally, humidity is not a factor unless something else is compromised. (Insulation, mold on a control board, cracked capacitors, etc.)
 

Chaos is Born

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Cincinnati, Oh
How many dimmer units are involved?
4 the most recent time, 2 previously

If more than 1, do they flicker in sync with each other?
in sync with each other

Is it an analog or digital control system?
Strand SLD Rack with Sin wave dimmers


The T pattern:

1, 2, 3
4, 5, 6

That pattern, Dimmers 1, 2, 3, and 5 flashing, all right above the control module.
 
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jmabray

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Chaos is Born

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the two in that pattern that were doing it before was: 2 and 5

Strand doesn't know whats going on, and it hasn't replicated itself when they have been here so they say they can't help us.

Its considered a Regional theatre. It is a city building so someone somewhere along the lines of getting equipment pulled some strings to get one Sin Wave Dimmer rack and two standard SLDs

We do mostly rentals of the space, and we have a local community theatre group that does their shows here that has first priority on dates. We've even done a few weddings in the theatre.
 

avkid

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Call the city electrician and have the power monitored for a period of time.
Voltage and frequency could be fluctuating.

And/or call Duke Energy to see if they have been having been problems(tis peak season)
 
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Jezza

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Jul 18, 2005
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Poughkeepsie, NY
I know in ETC racks, if you have a bad AF card installed, it will knock out a 'group' of dimmers or force them to behave eratically. I'm not quite sure how Sine Wave dimmers work in the Strand rack, but if there is any kind of electronic or computer controlled monitoring or talk back between the two units, then you should check and or swap out the cards. Try puting different dimmer modules in place of the ones that are acting eratically and see if that changes the symptoms.
 

JD

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North Wales PA
In sync with each other makes this real interesting! The dimmers themselves get off the hook. It is either a feed problem into a backplane on the unit, or a signal problem from the control mod in the backplane area. The backplane gets my vote. Assuming this is a 3 phase system, 2 channels would be on each phase leg, so if it had stayed on two modules, I would be looking at a distro problem, but 4! And in sync! That kind of eliminates the power as the source. Even if it was single phase, you would have 3 mods, not 4. Next time they are out to look at the unit, have them pull the rear off of it and look at the backplane (the common thing all the mods wire into.) Almost sounds like something got spilled into it. Sometimes a blown capacitor can splash its contents around and as the juice eats into things, the problem spreads. Also consistent with the humidity thing as the electrolyte will be more conductive (from dissolved copper) when humidity is high.
 

Van

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If those are removable modules, < sorry I'm not familiar with the strand setup> I would pull them and check for evidence of arcing on the power lugs and evidence of corrosion/ oxidation of the control contacts. I sounds similar to an isue I once had on an old rack with removable dimmers. one was arcing and causing the others to "brown-out" in sync with the arcing. he bottom line should be, as I think you know, it shouldn't matter what the realtive humidity it,< as long as it's below 93%> Humidity should have absolutely no bearing what so ever on the performance of a dimmer rack.
I interesting thing, to me, about this problem is that it's 1,2,3 and 5. Typically a power rail problem should be on 1,3,5,7 or 2,4,6,8 or something similar since the dims are normally connected to the rail in an even or odd patern to help balance the load across the feed. Which leads me to wonder if it's not a control issue, but again it should be all the dims connected to that pack, not just a select few.
 

jmabray

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Dallas, Texas
Not really. Power problems coming into the rack would generally affect the whole rack, or more than just the dimmers that he is having problems with.

The dimmers them selves are inherently stupid. What I mean by this is that they only do what they are told to do. The control processor or, what Strand called the "castle cards" (2 different parts in this rack) are both in line to control the dimmers. This sounds like it may be a castle card issue.

I would do some research in to which castle cards are controlling which dimmers and make sure that they are seated properly. It could be something as simple as the Airconditioning unit kicking on and vibrating those cards loose and causing some arcing in the contacts that is causing this.

I would also take those dimmer modules out and move them, swapping them with others. Does the problem follow the dimmers, or do the new dimmers in the same location have the same problem. If it follows the dimmers, then there is your problem, if it stays, then its a problem within the rack.

I know that intermittent problems are the worse to try and solve, but start there and see what happens and let us know...
 

Chaos is Born

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We have previously swapped out the dimmers with spare ones that we have and it does not follow the dimmer. We have also swapped out each Castle Card multiple times and still the same problem. We even moved Castle Cards to other racks seeing if it followed it there... Nope, stayed on the same rack.

I like JD's idea, and will have that checked out today if possible.
 

lightbyfire

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Jul 28, 2005
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Northern Virginia
That is very interesting. we had pretty much the exact same problem in our SLD racks and it was solved by trading the castle cards and the modules with new ones. what is your console? we have also seen some errant data that causes flickering in our house lights when commands are sent to certain channels in our stage racks. (300 series on shownet with AMX house control)
 

Chaos is Born

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Cincinnati, Oh
We have a 300 series, with AMX house control... however none of the lights flicker when we are changing things, its always after its been sitting for a while randomly it will flicker... we can't replicate the problem by doing anything, turning on the board doesn't do it, any commands on the board doesn't do it, it usually happens when the board is off... granted thats 95% of the time since we are in a slow season.
 

icewolf08

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If it happens when the board is off, is it possible that it is something as simple as electrical interference on your data cables? Or even a bad solder connection in one of the connectors? Also, if most of the time your console is off, then you must have some sort of architectural system for dealing with the house lights, so it could be a problem with that.
 

Chaos is Born

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Cincinnati, Oh
it happens when the board is off and when the board is on... and it is also always combined with a high humidity warning in the room...
 

jmabray

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Dallas, Texas
So if it happens when the board is off....

Has this happened since the system was installed? Were there any recent changes to the building that might affect the data line coming into the rack?

It sounds like there might be some interference in the data line somewhere along its path. Are you able to trace the conduit down all the way from the booth to the racks?

Is this rack being driven by DMX? or Network?