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Problems with DMX T-bar

Discussion in 'Lighting and Electrics' started by stradivarius, Aug 5, 2004.

  1. stradivarius

    stradivarius Member

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    Location:
    Stockholm, Sweden
    Hi,

    I have some serious problems with a Showtec 4 channel DMX T-bar. Some of the channels goes to full on as soon as I power up the unit, even when my lighting desk is off.

    Does anyone know how I can reset the unit or tell me how I can access the dimmer menu?

    It seems like the same unit is made by Botex (T-4) and Lite-Puter. Botex had a users guide for download, but the 3 pages didn't help me very much.
     
  2. DMXtools

    DMXtools Active Member

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    Location:
    Elgin, IL, USA
    If some channels are stuck full-on but the rest work normally, it usually means the triacs (one per channel) or SCRs (two per channel) are blown on the stuck channels. Triacs and SCRs are basically solid-state switches that dim the channel by turning it on and then back off again so fast you're eye can't see it (100 to 120 times a second). Brightness is controlled by changing the ratio of on-time to off-time.

    The normal mode of failure for a triac or SCR is a short circuit, i.e. - it turns on and stays that way, usually because it overheated and the guts all melted together. I think your best bet would probably be to send it in for repairs. It's not something you can "reset" for yourself (unless you have replacement triacs/SCRs and really know what you're doing).

    John
     
  3. stradivarius

    stradivarius Member

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    Location:
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    Thank you for your answer

    After some research on the internet I managed to figure out a way of reseting the unit, and I will test it today. I did read in the users guide that you can set the dimmer levels direct from the dimmer, and I think that someone before me did use this feature.
     
  4. DMXtools

    DMXtools Active Member

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    I hope it works. I'm not really familiar with the particular bar you're talking about, but it seems to me that the dimmers I've seen with this facility are set up so the direct setting is only active in the absence of a DMX signal - in case your controller goes out you can have a preset "scene" giving you some light on the stage.

    John
     
  5. ship

    ship Senior Team Emeritus Premium Member

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    Location:
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    I agree with DMX Tools, never heard of the equipment, but I would assume someone overloaded it, or with use it wore out and it than is acting characteristically of equipment that did not blow a fuse but is still functioning in at least some way with SCR or Triac. Link us to the site you found and let us know how the re-start worked out.
     
  6. stradivarius

    stradivarius Member

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    Location:
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    Hi,

    I haven't had the time to go to the theatre to test the reset procedure yet, but will do it on monday.

    It seems like the same unit is manufactured by Showtec (couldn't find a URL, but product name is "Showbar") and Botex: www.botex.com, product name: T-4.

    I'll be back on monday to tell you the results.


    Edit: just found a link to the Showtec site: http://www.highlite.nl/specials/T-bar_special.html
     
  7. stradivarius

    stradivarius Member

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    Location:
    Stockholm, Sweden
    Hi,

    It seems like you guys were right about the dimmer. I had another technician over at the theatre yesterday and he couldn't fix it either. So it was replaced by a dimmer rack.
     
  8. zac850

    zac850 Well-Known Member

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    Location:
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    Its good that you got it repaired so quickly. My school had that same problem on 2 of its 36 dimmers. I tried EVERYTHING I could think of to get it to work, checked the "test" modes to make sure that the dimmers weren't in any profile. Eventually it turned out that it was a faulty dimmer, and when ever I get a chance to get back in to school i'm going to have to replace it.

    I was very surprised that it was a faulty dimmer because we bought the dimmers new from ETC and they were broken. However, they did send us replacement parts that I just need to install into the dimmer, so it all worked out.
     

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