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Wacky DMX issue

Discussion in 'Lighting and Electrics' started by icewolf08, Feb 14, 2009.

  1. icewolf08

    icewolf08 CBMod CB Mods

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    Here is an interesting one. So, for the first time in 2 weeks of operation of the rig for the current show I started to have a wacky DMX issue. All of the DMX gear on one of my electrics just started to twitch. The electric is fed from one DMX line from an Opto-Splitter. There are two ETC Revolutions, an ICue on a SmartPower PSU, and 4 Chroma-Q Mk.II Scrollers on a Chroma-Q PSU. The chain goes: Opto>SmartPower (ICue)>Chroma-Q PSU>Rev>Rev. I didn't put a terminator in the last Rev as I have the ones with built in termination.

    The odd thing is that the "twitch" only shows up after everything is powered up for a while. Also, it goes away when I hard reset the Chroma-Q PSU. However, I noticed that when I powered down the PSU the "twitch" got worse until I powered it back up.

    More odd things. So last night, as I said, we had the same issue. I did a hard reset on the gear and it all worked fine for the show, we never saw the "twitch" again. So far today, after a reset it all seems to be working fine. I do a channel check before every show, and everything has always been working fine at channel check. After Channel Check, before the stage warmer, we have a cue for fight call, but we haven't noticed the twitch until we get into the stage warmer cue (though no one has been paying much attention to the lights during fight call).

    I don't know if I will have much time to troubleshoot today as it is a double header day and the show is 3 hours long. I probably won't be able to work on it in earnest until Monday. If you have any thoughts, let me know.
     
  2. Footer

    Footer Senior Team Senior Team Premium Member

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    Swap the port on the opto, I have had ports on optos get flaky after awhile. After that, sounds like a cable game. When you get the twitch, is everything wigging out at once, or is it device by device. Usually when I get "flashes" in the line, its a cable or opto issue. When you get random things in the line, its more of a termination thing.
     
  3. icewolf08

    icewolf08 CBMod CB Mods

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    The twitch consists of: Scrollers and Icue literally twitching, the lamps in the Revs flicker, and it looked like the lenses were twitching.

    As I mentioned before, it goes away after a hard reset of the Chroma-Q PSU, and doesn't return during the show. I can try a different port on the Opto. I wonder if it could be a corrupt data set in the cues, though it seems odd that it would only effect gear on one position that is addressed all over the place.
     
  4. mrb

    mrb Active Member

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    I have had this happen due to ground loop problems. Check your data cables and make sure you dont have one where pin 1 is connected to the shell, or the shield is touching the shell.
     
  5. icewolf08

    icewolf08 CBMod CB Mods

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    I will look into this.

    Here is an update. Second show is about to start, no fight call before this performance. Powered everything up and skipped the fight call cue, and everything seems to be working fine. So, I can't explain how a possibly corrupt cue would cause an issue like this that was isolated to one position.
     
  6. McCready00

    McCready00 Active Member

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    are you using 120ohms xlr5 cables?
     
  7. soundlight

    soundlight Well-Known Member

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    I've had issues with the DMX buffer card in a Chroma Q power supply screwing with a DMX signal before. When the issue started, it was similar to what you are describing. Switch out the buffer card with a new one from AC lighting. If that isn't the issue, it's always good to have a new buffer card around.
     
  8. icewolf08

    icewolf08 CBMod CB Mods

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    Thanks helpie. Actually I run my DMX on barbed wire insulated by garden hose. :rolleyes:

    This is interesting, do you think it would make a difference if I put the CQ PSU at the end of the daisy chain? I could get a new card, but if that is the case, i may as well just replace the PSU with an Apollo SmartPower 150, they are much better units (though slightly less wattage).
     
  9. soundlight

    soundlight Well-Known Member

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    In our case it didn't matter where in the chain it was. It was like it was passing dirt through as well as reflecting dirt back. It got so bad that nothing on that run worked.
     
  10. icewolf08

    icewolf08 CBMod CB Mods

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    This is good to know as my CQ PSUs are pretty old and have seen better days. Did you experience any other symptoms? Do you happen to know what the buffer cards run? Maybe I will call my local vendor on Monday.
     
  11. soundlight

    soundlight Well-Known Member

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    Just a slow deterioration to complete destruction of the signal chain. We think it may have also fried a channel or two of our opto-iso. We actually have a very strong suspicion of this - we think it blew a few capacitors in our ETC I10M Response DMX Splitter which distributes data for the whole venue.
     
  12. icewolf08

    icewolf08 CBMod CB Mods

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    That being the case i probably ought to pull the unit in question and replace it ASAP. The interesting thing is, they have changed the design of the PSU a couple times, I know that I have at least two different models of the PS08, will I be able to get the right parts to fix it, or should I just replace it?
     
  13. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Forgive a noise boy for interrupting, but if we have a strong suspicion that it's the Chroma playing up, then would it be feasible to home run that back to the opto? Terminate the Chroma on it's own to keep up to spec but maybe that might at least settle the rest of the rig...

    Now see that's the problem. Try some plain fencing wire instead, the barbs are making for variable impedance, less separation at the barbs and so lower impedance.:mrgreen:

    Oh wait, it's audio you could get away with running on wet string, your newfangled digital signal gets fussy about that sorta thing...:twisted:
     
    Last edited: Feb 15, 2009
  14. SteveB

    SteveB Well-Known Member

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    Are you using 120ohms xlr5 cables?
    Thanks helpie. Actually I run my DMX on barbed wire insulated by garden hose."

    I don't care what you use as long as you don't stick a set of 3 pin XLR connectors on it and call it "DMX Cable".

    SB
     
  15. soundlight

    soundlight Well-Known Member

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    We have an older unit, and AC lighting was able to get us the right buffer card, and now it works fine and we use it for all of our major shows. So just get the buffer card and see if it's the issue.
     
  16. Esoteric

    Esoteric Well-Known Member

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    I just stick my fingers between units. I am a better conductor than any wire ever made.

    Mike
     
  17. Malabaristo

    Malabaristo Active Member

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    The CQ PSU could potentially have damaged the DMX transceivers in your opto, but the capacitors failed for a different reason. They're part of the power supply circuit and due to the heat inside the device can dry out and fail after extensive use (typically 8-10 years or more). One could perhaps consider it a design flaw with the Response opto's, but a cheap & easy repair every ten years or so isn't bad for an electronic device.

    It's also possible that the signal degradation you were seeing was actually the result of those capacitors starting to fail. It's something that happens gradually and can cause intermittent operation for a long time before they fail completely.
     
  18. Kelite

    Kelite Apollo Staff Premium Member

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    No wonder I like to play in this park! :dance:


    Alex, we have updated and refreshed the SmartPower line to include 200W, 400W, and 600W power supplies for color scrollers. The circuitry has been designed here at Apollo and are assembled here in our building. The destruction testing for the 600W PSU ran hundreds of hours with hourly direct voltage shorts to test it's 'self-healing' abilities. If any range of power supplies would be considered bulletproof- this would be it.

    Please let us know if/when you get the problem resolved within the circuit!
     
  19. icewolf08

    icewolf08 CBMod CB Mods

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    Couple things, so, has the SmartPower 150 been dropped in favor of the 200? I didn't see the 150s on your website the other day.

    Secondly, the issue has not cropped up again and all I have changed is my power up sequence and fight call cue. It doesn't make sense because that would be very odd data corruption from the console. So, quite the intriguing situation.
     
  20. Kelite

    Kelite Apollo Staff Premium Member

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    That would be correct, Alex. The new 200W PSU supports 6x Smart Color scrollers, 400W supports 12 Smart Color scrollers, and the 600W supports 18 Smart Color scrollers.
     

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