Dimmer Flicker

[cw4u]

I recently put in a 48 channel dimming rack that is used for larger events at my church. All 48 ETA circuits will flicker about 2-3 times per hour. I don't know if it's the age of the units or what. Power is fed via CamLock to an electrical panel mounted inside the rack and then fed out to the dimmers.

Portable Rack Specs:
DMX Range: 1-56
3 - ETA DMX/Ultraplex (DMX Fed)
2 - Chauvet DMX-4 Packs (Addressed 49-56)
1 - DMX-lator (Addressed to start at 25)
3 - ETA Ultraplex/Analog (Ultraplex Fed)

Generally, our house rack (ETC Sensor) is addressed 1-96 but since some of the ETAs shut off above 100, I moved our DMX range for the house rack to 57-150. After that, I've got about another 100 channels forintelligent fixtures.

DMX Layout:
Console > DMX Iso-Split > Sensor+ Rack
> Moving Heads
> ETA DMX Dimmers > DMX-Lator > Chauvet > on-stage led washes

This problem has happened for years but seems to be worse this year than previous ones.

Any suggestions?

 

[silicsound]

To me it sounds like the Dmx data is dropping out or missing a frame. Which causes the portable system to flicker, while the sensor rack stays on as it uses the last frame it received for a couple minutes when it stops receiving data. Your movers may have a similar feature. It may be the the splitter, cable problem, or it could be a problem with the board. But that is just a guess.

However, put a Dmx terminator on the last piece of your portable setup if you haven't already.

I recommend that you call a professional to take a look at it, they'll know whats is going on.

 

[mstaylor]

I read it originally that the flicker was in the portable system but you said that was recent and the flicker has been there for years. So we need to clear up what is going on. What is new and what is old? What light board are you using? It could be a clock speed problem with the Chauvet dimmers. How to proceed depends on if the whole thing flickers, or just a portion.

 

[cw4u]

Stuff added this year:
4 - Moving Heads
6 - LED Washes
2 - Chauvet Packs (free)
Enttec USB Pro
LightFactory Control Software
DMX Splitter

The flicker does reside in the ETA dimmers in the portable rack. (Not LEDs or Chauvet) It usually is just one circuit flickering but I've seen all 48 ETA circuits flicker. One of our engineers made up a terminator that went into the DMX-lator but I took it off since I had to use the output to go back into our LEDs. Should I attach the terminator to the end of the chain? Also, even with the terminator I still had some random flickers (2 or 3 times a show) throughout the production.

 

[silicsound]

Yes you should put the terminator back on, its not required but it helps avoid signal issues.

I also did some research on ETA, which leads me to believe that is an internal timing error, that is common. The only fixes I can find is that some equipment has a jumper that turns on a 1 Sec data loss fade time. The only other thing could think of is to change the baud rate on the console, but its unlikely that it will help.

I also found this thread which sounds like the same problem. Send a PM to Les he may know something about whats going on.
http://www.controlbooth.com/forums/lighting-electrics/19162-eta-dimmer-pack-issue.html

 

[mstaylor]

Put the terminator in at the last point in the chain. If this doesn't fix it then disconnect all of your dimmer chain, including the splitter. Take the DMX straight to the problem dimmer and take everything else out so you can see if the different type dimmers are not playing nicely. If it turns out that it is a DMX speed problem, I believe Doug Fleener just built something that fixes that problem, but before you spend more money, let's try to isolate the problem.

 

[David Ashton]

flicker is commonly caused by failed snubber capacitors allowing spikes to false trigger other dimmers, especially on older dimmers, it may just be a case of changing out these capacitors.[by a competent person of course]

 

[Les]

I also found this thread which sounds like the same problem. Send a PM to Les he may know something about whats going on.
http://www.controlbooth.com/forums/lighting-electrics/19162-eta-dimmer-pack-issue.html

Unfortunately, I've pretty much abandoned those dimmer packs in my storage unit, but I sure would like to fix the problem in the event that I want to sell or use them! I've actually been following this thread for a possible fix .

I don't remember how I described my problem (haven't opened the link in a long time), but it was like every channel would just blink. Not really within a certain interval, but all channels would do it at the same time. It happened at any intensity. It happened on only the one pack, whether it was in a chain or the only one connected to the console. Funny thing is, it would only do it on a console. Test mode was fine. I connected it to two different consoles -- same issue. David might be on to something with the capacitors. It's a very quick flicker -- almost a mind game making you wonder if it really just did that.

 

[David Ashton]

I mentioned that because on Strand JTMs there was a .1 capacitor across the control transformer, if that blew everthing would continue to work fine except for random flickering

 

[cw4u]

I'll try to look at those capacitors sometime. If that doesn't fix it, I'll probably just request to replace that rack next year. It's served us for a very long time (over 15 years I believe) but with it's addressing and flickering issues, I feel it's time to let it go.

 

[cw4u]

Also, I had one of the ETA packs go into test mode all by itself today during a service. Any reason why that might be?

 

[icewolf08]

Have you considered that the flicker could be cause by voltage inconsistencies in the building? You say it happens a couple times in an hour, could this be when your HVAC system kicks on? It is possible that this particular rack is just more sensitive to spikes/dips in it's feeder than your other racks.

 

[cw4u]

Interesting idea. I'll have that looked at.

 

[tjrobb]

In that vein, every time our LD goes into a 'heavy' cue we can see our index rail lights dim. Something short like a motor start would easily cause more of a flicker.