Control/Dimming Flickering Lights

[thelatinist]

First of all, thanks to all of you for your suggestions. I'm sorry my first post has to be such a head-scratcher. You guys have been great, though.

It also would not hurt to reboot the dimmer rack. Even the most stable, microprocessor based system can get a snit and need its head cleared. Always try the simple, easy stuff first.

Rebooted three times, plus was off and completely pulled from the rack for an hour yesterday, dusted and contacts cleaned, then reinserted.

Since you have an active splitter, that eliminates the movers and their cabling. It narrows the search to the console, the splitter, the dimming rack, and the DMX cabling between the three.

Is the DMX cable from the splitter terminated at the dimmer rack? There should be resistor across the DMX line at the terminal strip inside the rack. I would also check that the switch for termination is turned on for the splitter input.

I will check for a resistor on the DMX line in the rack tomorrow. There are two 4-output Pathway 1002 Octo-Splitter modules in the enclosure. One has its its termination switch on, the other off. Is that a problem? But then, yesterday was the first time that enclosure has been opened in the four years I've been here, and we've not experienced this problem in the past.

It could also be a power problem. Are all of the lights that cause it to act up powered from dimmers on the same phase? Assuming this is a three-phase rack, phases are bussed to columns of dimmer modules, in the pattern left to right A, B, C, A, B, C. If the culprits are all on the same phase, then consider having a qualified electrician inspect the feeders to the rack and the circuit breaker for it.

The rack is three-phase capable, but three-phase is not available in our area so it was configured for single phase. The affected channels are scattered across all of the bus bars.

You could try re-patching the board / trying a different board? If the same channel in the board is doing it it might be the board, but if it does the same instruments / circuits its outside of the board... Idk if that makes sense...

We've got a previously-ordered DMX-over-Ethernet box on its way, and will use it to cut the console out of the chain when it arrives. Meanwhile we have tried opening a couple of old show files but have had the same issue. If it does turn out to be in the console I will start fresh and re-patch everything.

I logged this earlier, now disappeared, the most obvious, common problem causing flickering is a bad neutral connection in the dimmer and this could cause load related flickering, another vaguely possible fault is an earth neutral swap on a light, sending current down the earth and lifting it.

If we can narrow it down to a single fixture/dimmer or set of fixtures/dimmers we will certainly check that. Thanks!

 

[DPickering]

I have a couple of questions concerning your flicker problem.
Is it just the Coemar fixtures that flicker or other load types?

If it is the Coemar fixtures that flicker, if so which dimmer rack do you have? Depending on the dimmer panel or rack, are the Coemar fixtures connected to non dim module, SCR or IGBT dimmer module or a constant circuit breaker? The Coemar fixtures should be connected to a constant or switched power source and I wouldn't recommend that the Coemar fixtures receive its power from a dimmed circuit even if you configured the dimmer to operate as a non dim output. It takes about three cycles to reach the full AC output on a dimmer module. Some switching power supplies in automated fixtures don't know how to handle this and this may be what is causing the flicker.

We can be reached at 1-800-4-Strand (787263) if you would like to call us.
Thanks
Doug Pickering
Strand tech support

 

[thelatinist]

I have a couple of questions concerning your flicker problem.
Is it just the Coemar fixtures that flicker or other load types?

If it is the Coemar fixtures that flicker, if so which dimmer rack do you have? Depending on the dimmer panel or rack, are the Coemar fixtures connected to non dim module, SCR or IGBT dimmer module or a constant circuit breaker? The Coemar fixtures should be connected to a constant or switched power source and I wouldn't recommend that the Coemar fixtures receive its power from a dimmed circuit even if you configured the dimmer to operate as a non dim output. It takes about three cycles to reach the full AC output on a dimmer module. Some switching power supplies in automated fixtures don't know how to handle this and this may be what is causing the flicker.

We can be reached at 1-800-4-Strand (787263) if you would like to call us.
Thanks
Doug Pickering
Strand tech support

The Coemar fixtures are not on dimmed outlets or even on the same utility feed. They are also isolated with an opto-switch and have been completely unplugged from DMX since Friday so that we could eliminate them as a possibility. It seems to only happen when our SkyCyc fixtures are on -- twelve channels in all. I'm about to load those circuits with StarPar fixtures to see if we can recreate the problem without the SkyCyc fixtures. If it is still happening then I will definitely contact customer support.

 

[thelatinist]

So I removed the SkyCycs from six of the channels I thought were the source of the problem and replaced them with fresnels and StarPars. I was able to duplicate the problem with those six channels set to full and my other SkyCycs off. Moreover I was able with lots of effort to get the flicker without any of those channels on at all but with nearly everything else we've got hung at full. It was much less consistent, but it was there. So it seems that the issue is not those particular channels, but is merely aggravated by the heavier load -- and the SkyCycs are 18 kW all by themselves. Since it appears to be load-related, I don't think it can be the console.

So where does that leave me? I think I'm going to have to call for service after all.

 

[DavidNorth]

So I removed the SkyCycs from six of the channels I thought were the source of the problem and replaced them with fresnels and StarPars. I was able to duplicate the problem with those six channels set to full and my other SkyCycs off. Moreover I was able with lots of effort to get the flicker without any of those channels on at all but with nearly everything else we've got hung at full. It was much less consistent, but it was there. So it seems that the issue is not those particular channels, but is merely aggravated by the heavier load -- and the SkyCycs are 18 kW all by themselves. Since it appears to be load-related, I don't think it can be the console.

So where does that leave me? I think I'm going to have to call for service after all.

At this point, based solely on your descriptions, it's more than likely going to be one of a couple of things......although I might miss something.

- Console issue or DMX timing issue. Get another console in there and try it [preferably not the same make/model]. If everything works ok, then your console is the issue.
- DMX wiring. You've modding the wiring in the facility, it sounds like, and possibly something didn't go quite right. Maybe there is a shield touching ground [heatshrink is your friend], or data wires are open/touching, etc. Not leaning towards this since the problem sort of sounds like it changes under load.
- Have an electrician tighten all the feed and load lugs in the rack and all the feed lugs in the panels that lead up to the rack. This fixed an issue up in Canada recently. Aluminum wire does tend to cold flow over time, especially with heat and vibration cycling, and even though copper doesn't cold flow as readily, it is still susceptible to the same issues. Not sure which you have but an occasional check of lug torques is never bad.
- Lastly that probably leaves the C21 processor. And that's where you would want to calling Strand.

Let us know how you do,

David

 

[thelatinist]

Had an electrician in today. All connections are solid, but he discovered that we've got anywhere from .2 to 2.1 amps running down the ground wire from the rack (load dependent -- higher the load, higher the leak). Since all our instruments are grounded to our grid and there's nothing running back through ground from our undimmed outlets, that leaves the rack/processor itself. Guess we'll have to contact Strand after all.

 

[Kelite]

Had an electrician in today. All connections are solid, but he discovered that we've got anywhere from .2 to 2.1 amps running down the ground wire from the rack (load dependent -- higher the load, higher the leak). Since all our instruments are grounded to our grid and there's nothing running back through ground from our undimmed outlets, that leaves the rack/processor itself. Guess we'll have to contact Strand after all.

SO- we're getting near the answer!

The .2 to 2.1 amps running down the ground reminds me of an issue at the The Klipsch Music Center (formerly Verizon Wireless Music Center and originally known as Deer Creek Music Center). This outdoor amphitheater, owned by Live Nation, is located in Noblesville, Indiana. A few years ago a barefoot concert-goer was electrocuted on the grandstand stairs when damp feet found some type of voltage leak... (Tried to find a news link, but this event appears to have been 'scrubbed' from history.)

 

[DavidNorth]

Had an electrician in today. All connections are solid, but he discovered that we've got anywhere from .2 to 2.1 amps running down the ground wire from the rack (load dependent -- higher the load, higher the leak). Since all our instruments are grounded to our grid and there's nothing running back through ground from our undimmed outlets, that leaves the rack/processor itself. Guess we'll have to contact Strand after all.

Excessive ground current may or may not be a rack problem. The issue could easily be elsewhere such as some fixtures having a ground and neutral swap in their connectors [seen it many times], wire breakdown in fixtures or cables, or more than likely, induction picked up in wiring in adjacent circuits that is expected.

Devices plugged into the dimmer rack that are CE compliant and have Y caps can easily create this. Normally this would be found in LED fixtures and Movers. However, if you have only tungsten fixtures, this will not be the case. It is possible that the dimmer rack [modules] has Y caps in it, if it was originally designed for the CE market, but I highly doubt this.

I would still like to see you try another console to make sure there is no problem there or with the DMX wiring, but then that really does leave the C21 processor.

David

 

[thelatinist]

SO- we're getting near the answer!

Yeah. Thank you all for your help. I'm glad I found ControlBooth; you all have been great, and the pros here are very helpful. When I called Strand the phone was answered by none other than the same Doug Pickering who responded above. We talked for half an hour and he's now contacting the subcontractor who did the install to see if they can figure out the issue.

 

[DPickering]

Thanks for calling me this morning about your system and the problem there. I was able to reach the original start-up tech. He is on his way back to his office and will pull his records of this project and contact you later today.
I agree with Keith and am also concerned that you may have a grounding problem to the C21 dimmer rack.
Thanks
Doug Pickering
Strand tech support

 

[thelatinist]

However, if you have only tungsten fixtures, this will not be the case.

Yeah, all tungsten.

I would still like to see you try another console to make sure there is no problem there or with the DMX wiring, but then that really does leave the C21 processor.

Yeah, we're going to try another DMX output as soon as we can arrange one. Meanwhile we're talking to Strand and they're reviewing our installation to see if they can think of anything short of the processor that could be the issue.

 

[thelatinist]

I agree with Keith and am also concerned that you may have a grounding problem to the C21 dimmer rack.

Yep, this is why we've turned the main off. Don't want to mess with stray voltage, especially in a school!

 

[thelatinist]

So after six hours with the electrician it appears that the current in our ground line is probably not due to a short but to induction in the conduit with the mains. There is no voltage across ground and neutral, and the amperage in the ground seems to vary proportionally with load. At this point it's looking more and more like the processor is the source of the problem and the ground issue we thought we were having is unrelated.

We're going to try another DMX source to rule out the console definitively, but we were still having the flickering when we had the channels powered up through local control on the C21 front panel and the DMX switch turned off, so that seems pretty unlikely.

Thanks again to everyone for your help. I'll keep you posted.

 

[thelatinist]

So after digging out from under three feet of snow we finally received the loaner C21 processor the folks at Century Lighting in New Jersey had shipped to us. Popped it in, tried with with two DMX sources and local control and...

the same problem.

Thankfully Joel from Century Lighting, who installed our system six years ago, will be able to come up some time this week to get this sorted out once and for all. Thanks to Doug and to everyone else here who offered advice here. I'll let you know how things turn out!

 

[hobbsies]

Thanks for the updates, looking forward to hearing what the problem is.

 

[thelatinist]

So Joel made it up on Thursday of last week -- Valentine's day, no less -- and we spent six and half hours together trying to figure out our issue. The problem with trying to diagnose it was that we neither we nor he could find a way to reliably reproduce the problem. It happened, and frequently, while he was there...but there seemed to be very little or no pattern to when it happened. Sometimes we would think we'd identified a pattern, only to have it disappear or change on us. Ultimately he swapped out all of the electronics in the rack with his own, eliminated all our control wiring, and ran the rack from his DMXter using the internal connectors, and after a lot of pulling, swapping, and reinserting of dimmers, we concluded the following:

1. Only one leg of the rack (the left) is affected.
2. When dimming up, we consistently got a flash at between 14 and 19%.
3. When the lights flashed, there was a brief spike of voltage across ground and neutral.
4. As far as he can tell, there is nothing wrong with our dimmer rack.
5. He's never seen anything like our problem in his 40 years on the job.

At this point there's nothing we can do before our show this Friday and Saturday. Joel (and Doug from Strand) suspect that it is a transformer issue and are recommending a recording line monitor between our transformer and the rack...but that will take time to arrange. Meanwhile, since we were able to determine that the right side of our rack is working well, we spend Friday-Sunday moving outlet boxes, running extensions and otherwise rearranging our lighting so that we could light the show using only one leg. Fortunately this show is not particularly demanding and we are able to do without some of of our fixtures. As it is, we're using all 48 channels on the right leg of our rack.

Once the show is over we will get our electrical contractor in to inspect our transformer, and also to swap the left and right legs of the feed to see if the problem moves with it, as Joel and Doug recommended. Then we will see if we can get a line monitor. And ultimately, if we can rule out everything on our end, we may have to do battle with CL&P over what appears to be a dirty feed.

Thanks again to everyone for their support. I don't feel so bad about not being able to figure this out, since it has ultimately stumped even the folks from Century Lighting Service and from Strand. I just want my lights back!

 

[Brandofhawk]

So Joel made it up on Thursday of last week -- Valentine's day, no less -- and we spent six and half hours together trying to figure out our issue.

Sounds like a romantic date with the dimmer rack.

 

[Lazerlight]

This is just a suggestion since a similar problem happened to our facility yesterday. We have the c21 processor as well. Our facility runs five universes, It turned out to be another light board in our facility was patched to the same universe as the board we were using at the time and the channels that overlapped on the boards were fighting for control hence the flickering.

This is just a suggestion however.

 

[thelatinist]

Thank you for the suggestion. We have only one universe, however, and we're only running one console. We also physically disconnected all control inputs from the C21 while trouble-shooting and duplicated the problem both while controlling the lights locally from the C21's and via a DMXter plugged directly into the board.

The show is now over, and came off quite well. We ran 310 amps all on our right leg -- we even had to twofer some fixtures to cover everything -- without a hitch or any sign of a flicker.

Monday we start trying to get our power situation fixed before the spring show in May.

 

[David Ashton]

I used to get this problem on Strand jtm dimmers when the .1mf snubber capacitors had blown open circuit this would cause random flickering. worth a look,
correction, it was the snubber capacitor across the transformer feeding the dimmer module.