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Strand dimmer rack weirdness

Discussion in 'Lighting and Electrics' started by gabe, Dec 6, 2007.

  1. gabe

    gabe Member

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    So today I walked into sixth period and my director told me the general contractor had called and I needed to go up and "show him how to turn off the red strip lights." I quickly assumed I had left a sub up from working in there and it would be a simple matter, I was mistaken.

    It turns out that the board (subPallete) wasn't even on, and when I turned it on and tryed to turn the light off nothing happened. So that was odd, I went into the electrical room and tryed setting the level of the dimmer from the C21 rack, nada, light still on. The only way I could get it to turn off was either flipping the breaker on the dimmer or physcially removing it from the rack.

    Phone calls to strand are already being made but I was wondering if anyone else has had a similar experience.

    I dunno what is relevant but here is some basic info about the space:

    Strand subPallete board.
    2 96 dimmer C21 racks.
    2 universes of DMX throughout the building.
    strand 301 console in stage managers pannel backstage.
    Not sure what else is important...

    Thanks,
     
  2. icewolf08

    icewolf08 CBMod CB Mods

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    Probably a blown dimmer cube (SCR), they like to blow closed so the lights would stay on. It can be a relatively simple fix if you know what you are doing, if not, just take the dimmer module to your local Strand Dealer and they can take care of it.
     
  3. Footer

    Footer Senior Team Senior Team Premium Member

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    Strands are usually very easy to do yourself, and if you order a new part odds are you can figure out how to do it very easily, just be sure to also order some thermal paste with it. Take the dimmer out and swap it for another in the same rack, see if the problem moves or not. If it moves, you have a bad SCR, if it stays the same, its in the control module, do a full reset of the system and see if that takes care of it.
     
  4. jmabray

    jmabray Active Member

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    if it is a C21 that should still be under warranty. Most of those racks are under 2 years old.....
     
  5. Grog12

    Grog12 CBMod CB Mods Premium Member

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    Point of anat retentive saftey....don't remove the dimmer if you haven't flipped the breaker.

    Do the C21's have a signal light?

    I agree with Footer though swap out dimmer packs and see if the problem shifts with the dimmer or not.
     
  6. gabe

    gabe Member

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    The rack is about two months old, the building isn't even done yet. I really hope this isn't a pattern to expect as we move into our new home...
     
  7. JD

    JD Well-Known Member

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    Although we generally think of blown SCRs being the victims of over-current, they can also be blown by over-voltage. (Voltage surge) This can happen even when the equipment is off as long as the breaker is on and there is a load attached. As this is a new building you may want to look into having them install a MOV panel mount surge suppressor on the panel that feeds the packs.

    SCRs have a PIV rating. (Peak Inverse Voltage) Usually 400 to 600 volts. If this voltage is exceeded, pop, its gone, even if it was only feeding a 100w light bulb. (In other words, almost no load is needed.) MOVs kick in at about 330 volts, and clamp at that point. These may all sound like voltages that would never be found on a 120v loop, but high voltage transients exceeding this are very common, especially when big inductive motor loads are on the same distribution. A 10ms spike will go unnoticed by most equipment, but its enough to pop an SCR.

    Sample Device:
    http://www.levitonproducts.com/cata...sid=F6DC264F0C282ABAD240D1A4A308D63E&pid=1208
     
    Last edited: Dec 9, 2007
  8. Footer

    Footer Senior Team Senior Team Premium Member

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    Ya... get the lighting company that installed it back in there... They should be at your call for about the next year.
     
  9. cutlunch

    cutlunch Active Member

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    As older members we need to remember not to suggest people do things that they don't have the experience for. Maybe swapping modules to find a faulty one can be safe on some dimmers on others it would expose untrained people to risk of hurting themseleves or damaging the equipment .

    Replacing parts on modules should be left to qualified technicians if you don't have a trained person standing right next to you. Also you void all sorts of warranties.

    In this case if the units are only two months old Gabe you should leave them alone and tell the installer. If you start mucking around with them they might come back at the school and say they were working when they put them in but some kid's been playing with them.

    Also I am curious if the building is not finished how come you are using the dimmers?
    I ask this because someone else mentioned spikes killing the SCR's, TRIAC's. If the dimmer packs are being turned on while they are still doing the building you may be getting spikes from building equipment. Also is all the wiring finished?
     
  10. Lightingguy32

    Lightingguy32 Active Member

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    We have similar problem with dimmers (not SCR related). When ever the power goes out or if our houselight (ETC unison DR6) hits an error. Resetting will throw our Strand Premier (panick system) hay wire. By now we have figured out our school administration was trying to cut corners and save money, but it led to compatability issues between the Strand Premier system and our ETC Unison DR6 houselight rack which has its own arch/theatrical command module. The lesson learned is ETC Unison dimmer racks and Strand premier panick systems do not get along with each other.
     
  11. fredthe

    fredthe Active Member

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    On a Strand C21 (what he likely has), the "training" for removing modules is:
    1. Turn off breaker on face of module.
    2. Grab handle and pull.
    Reverse above to install.
    That said, certanly call the delaer who installed it... even if you have already found the fault, so they can permanently correct any issues.
     
  12. cutlunch

    cutlunch Active Member

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    Hi. Taking what you say at face value you have proved my point.

    From what you have written you have not mentioned turning the main power to the dimmers off. You talk about the circuit breaker on the module itself . To me this means that you will be un/plugging a module that still has power at its connectors. Even registered electrical contractors don't work on live equipment unless they have to.

    It may be fine in this case but is it good practice and is it what we should be teaching students?

    Surely the safer steps would be take all channels to zero using the control board or controls on the dimmer.
    Turn off the main circuit breaker that suppiles power to the dimmer rack we are working on.
    Then carry out your steps.
    Then after the module is re-installed turn on the main circuit breaker.
     
  13. jmabray

    jmabray Active Member

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    Most dimmer racks these days are designed to have this procedure done every day with out turning off main power. This is how I tell everyone I have ever trained on either a Strand or ETC system to replace a dimmer module (or move it to another location.) I do also mention not to stick your hands in the rack as their is live voltage in there that can kill you. But what he has described above is a perfectly good practice.

    This is different from working on a live circuit. What you are doing here is not really "Working" on live electricity, especially in the way that an electrician would "work" on a live circuit.

    You're (espeically with Strand) in relatively little danger of shocking anything.

    Are you going to be safer turning off the main breaker? Probably. But I would trust student to change out a dimmer module before I would trust them to throw a 400 amp disconnect.
     
    Last edited: Dec 10, 2007
  14. icewolf08

    icewolf08 CBMod CB Mods

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    The addressing is done by slot in the CEM or Castle Card, or whatever the dimmer control module is. I believe in the Sensor+ racks you can change the channel order of the dimmers using the web interface, but I haven't tried. So the short answer to your question is yes, you can pull every dimmer card out and rearrange them and put them back and the oder will remain the same.

    The only time this isn't true is if you have specialty dimmers. A 6kW dimmer usually takes up the same space in the rack, but is a single dimmer on a card instead of two dimmers, so you can't put a 6kW dimmer in the slot for a dual 2.4kW dimmer.
     
  15. JD

    JD Well-Known Member

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    In theory at least, it might help a bit. Probably not practical. If overcurrent or overvoltage doesn't blow the SCR first, the eventual failure comes from thermal cycling. The silicon subtract eventually fractures from the case. The question is; will it be in our lifetime? If so, then the more current a dimmer sees, the more thermal cycling it goes through, and rotating heavy use and light use dimmers will increase lifespan. I suspect the equipment will have outlived its usefulness before this happens.
     
  16. icewolf08

    icewolf08 CBMod CB Mods

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    Yes, the wiring is different. A 6kW dimmer requires wiring and connectors that are rated for 50A. Also, the rack is wired differently because the standard dimmers are two per card where the 6kW dimmer is one dimmer per card. This, however does not mean that the 6kW dimmer won't fit in any slot, so you have to pay attention.
     
  17. fredthe

    fredthe Active Member

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    You read what I wrote exactly the way I intended:). There is no reason to turn off the main power on a C21 rack before swapping modules. After all, what do you do if a module blows during a show...
    The C21 (and, I believe ETC's comparable dimmers) are designed specifically for this. Yes, you can touch live AC if you really want to, while the module is removed, but you would have to reach through the module opening, and all the way to tbe back of the rack to do so. If someone is stupid enough to do that, then they just don't belong in the dimmer room.
    We should be teaching students how to use the equipment appropriatly, not to be deathly afraid of it. Respectful, yes. Afraid, no.
     
    Last edited: Dec 10, 2007
  18. jmabray

    jmabray Active Member

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    A 6KW dimmer will not fit in the same space as a 2.4kw. I believe that code prohibits this. Irregardless of that though, manufacturers will not let it happen. In Strand racks, the pins won't line up. In ETC racks, the dimmer modules are keyed differently so as not to be able to fit one into the slot for another. (I guess I shouldn't say that all manufacturers won't let it happen, but the ones that I am familiar with, won't)

    50 amp dimmers drive all sorts of loads. In larger theatres and TV studios and the like, 5K fixtures (fresnels, typically) were not that uncommon a few years ago. However, with the advent of better cameras and the like, those are becoming less and less common.

    And as was said before, dimmer modules are inherently stupid. The are told what to do by the control modules. They have no on board addressing electronics. (again mostly talking about ETC and Strand here) They are made to be quickly swapped in an emergency situation.
     
  19. icewolf08

    icewolf08 CBMod CB Mods

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    Hmmm, I was told by an ETC rep that it was a simple matter of rewiring the backplane of the rack to convert a 6kW dimmer slot to a dual 2.4kW slot. I haven't looked at it yet, nor have I ever tried to put a 6kW card into any other slot. Now I have to go look for myself.
     
  20. jmabray

    jmabray Active Member

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    I believe that is true. My point was that you couldn't just swap them around. i.e. pull a 6k module and put it in a 2.4k slot. The wiring you are speaking of is not something that you really want to try and do...
     

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