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Control/Dimming Grand Master fader issue on Strand MX

Discussion in 'Lighting and Electrics' started by stevefox, Oct 13, 2008.

  1. stevefox

    stevefox Member

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    Last Thursday my school held it's first event requiring the tech group. I noticed this late last year, but didn't get the time to really look at it until now. When bringing the Grand Master fader on our Strand MX board up or down, the light's levels will jump around. For example, bringing the fader up from 0, the lights won't come on until 3 or 4, and then pop on, then between 5 and 10 will pretty much jump to any level and produce a flickering effect. It only does this with the Grand Master, and a smooth fade can be accomplished crossfading between the A and B set of faders.

    Basically, I'm asking if this is something we can fix ourselves, or do we have to send it in or get a new board?
     
  2. Sony

    Sony Active Member

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    Sounds like it's almost definitely a bad fader pot to me. I would suggest sending it back to Strand or better yet replacing it completely if possible. It's not really something you can fix yourself because it is soldered onto the board.
     
  3. waynehoskins

    waynehoskins Active Member

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    Sounds like a dirty pot to me. What I'd do:

    First try blowing that pot out. It probably won't do anything, but sometimes you'd be surprised what that will do.

    Failing that, I'd try cleaning the pot, if it were my board, with tuner cleaner -- but in your case, being a school console, I wouldn't. I would either consult the service manual or Strand tech support to see what procedure they recommend for cleaning a dirty pot on that console. I've heard rumors that certain types of cleaning solutions (tuner cleaner, Deoxit, Cramoline, etc.) can damage certain types of pots, so since it's not yours, I'd let the manufacturer tell me what to clean it with. Actually, I'll revise that. I'd let the manufacturer tell me what it shuold be cleaned with, then present that to whoever it needs to be presented to for approval (in case it breaks, you know), and proceed only if I get that okay -- it may well be a good occasion to get a new board.

    If it's beyond cleaning (which is rare), if it were my board, I'd replace the pot. Or convince myself that I really didn't need the GM.
     
  4. FMEng

    FMEng Well-Known Member Fight Leukemia

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    I concur that using electronic cleaners not made specifically for faders and pots is not a good idea. That said, Caig makes a product intended for that use. I have not tried it, but I have had good luck with their other products.

    I know the Strand MX very well. The grand master isn't terribly important on that console, so the safest course of action is to just avoid using it. If it gets to the point of being so flaky that it affects console operation without being touched, then I'd try the cleaning spray. If you wind up sending the console out for repair, having tried cleaning it yourself won't hurt anything.

    As a last resort, I would carefully cut the circuit board trace to disconnect the fader wiper, then jumper the other side of the cut trace to the top leg of the fader resistance, using 24 guage solid wire. That would effectively remove the fader from the circuit. Keep in mind I don't have a schematic, so this is risky. If done carefully it can be reversed.

    Whatever you choose to do, try it when you have a few weeks of down time to resolve it if it makes things worse. Don't do it the day before the big show.
     
  5. EdSavoie

    EdSavoie Well-Known Member

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    I'm cringing as I break my personal code of conduct on necroposting, but it appears to me that given the topics covered on here, nobody is particularly bothered by this.

    I summon this thread back to the world of the living to add that this is also happening to our Strand MX console, though it only occurs from the 80-100% range on the slider, causing the GM to dip anywhere between 50-97%, generally preventing the output level from going above 90% (confirmed using an old serial console!)
    Because of how bad the flickering can get, I'm not sure if it's truly an issue with the pot getting dirty, or if the connection is loose.
     
  6. Cryophallion

    Cryophallion Member

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    A loose connection should show as more flicker than dip I would think, as it would lose connectivity, and usually that means going to 0, not necessarily dimming. I give Strand credit, those boards are still kicking. And usually in spaces with Blue TTI racks interestingly enough...

    I mean, you could take it apart if you dared to check the connection, but if you are not good with a soldering iron (and the proper one), that may not be the best choice.
     
    Last edited: Nov 10, 2016
  7. Cryophallion

    Cryophallion Member

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    Why do you think I said you'd have ot be good with it ;)
    Yes, I meant soldering iron. I was looking at my workbench and saw one sitting out and had a slip of the keyboard... Good call. The person I used to know who was amazing at fixing those boards is no longer available, but there are several good strand repair people out there.
     
  8. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    It was the notion of someone working in an MX, GSX or LBX with a typical Weller single or dual wattage soldering gun with a tip similar to a chunk of coat hanger wire and a hulking big transformer in its handle magnetically coupling into the board's sensitive electronics that caught my eye and prompted my caution. If you haven't already, perhaps you wouldn't mind going back and editing your post to clarify for posterity. If you clarify your post, I'll delete my reply, including your quote, and all traces will be gone like it never happened. Many people would never consider the problems associated with a soldering gun's transformer inducing potentially destructive levels of current into a boards components and thin, narrow, traces. They'd likely consider problems from excessive temperature and overly wide application of heat but few would appreciate the problems of magnetic coupling / radiation.
    Toodleoo!
    Ron Hebbard.
     
  9. MikeJ

    MikeJ Well-Known Member

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    Probably a dirty pot. At the point where it happens, try wiggling the fader, if it jumps around its a dirty pot. Usually Slide pots have the electrical connections AND body of the fader soldered to the board, so a loose connection outside of the fader itself, is unlikely.
    Do, not spray any cleaners into the pot. Usually the way they are constructed, the cleaner won't get into the contact area, it will just wash away the grease that makes the fader slide smoothly. You can clean some faders with success, but means removing it from the board and dissembling it, so you might as just replace it at that point anyway.

    If you are decent at soldering, and have a solder sucker, this can be done. Its really pretty easy, but If you have not done a lot of PCB soldering, you may want to practice or hire a professional. Electronics repair probably bills around $100/hr, and a fader is probably <$20, if its commonly available. If you are confident in the diagnosis of a bad fader, and can disassemble the console, you could just bring just the PCB to an electronics repair shop, and have them change out the one fader. They would probably only bill you for 15 minutes.
     
    RonHebbard likes this.

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