Heat lockout sensor in a studio monitor

Discussion in 'Amp Central Station' started by robert donithan2, Apr 13, 2019.

  1. robert donithan2

    robert donithan2 Tele-Meister

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    This may not be the right forum but here goes-where is the heat lockout sensor in a powered studio monitor? My monitors have these and I believe one of them has malfunctioned.It used to engage and then 30 minutes later the monitors' speaker would come back on...then it started doing it more an more until it locked out altogether...any help?
     
  2. W.L.Weller

    W.L.Weller Tele-Holic

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    This is the kind of thing usually addressed by the OEM in a warranty situation. Without more specifics, it's hard to be more specific.

    If you are the kind of person who feels like "it's already broken, it can't work any less than it does now" and there's no warranty option, by all means, crack them open and look for a fuse or some other melted part.

    If you wind up replacing the monitors, take a hard look at the amp you're driving them with before hooking up the new ones.
     
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  3. robert donithan2

    robert donithan2 Tele-Meister

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    I already opened it up and pressed on the circuit board and looked for burned components , tested speaker wires etc.I'm aware that it is bi-amped but it progressively faded out resembling the heat lockout mode.Warranty expired.The woofer "pops" when I shut I'd off so I would think the fuse isn't it.It lights up in front indicator.
     
  4. dogmeat

    dogmeat Tele-Afflicted

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    what are they. if we had a diagram it's a lot easier to take a wag
     
  5. robert donithan2

    robert donithan2 Tele-Meister

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    They're Sterling MX-5.I haven't found a diagram yet.
     
  6. robert donithan2

    robert donithan2 Tele-Meister

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    They're independent of an amp.Powered studio monitors Sterling MX-5.
     
  7. Blrfl

    Blrfl Tele-Holic

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    If it's going into thermal overload, don't expect to find anything visible. The cutoff threshold will be well below the point of physical damage and may happen in stages. Continuing to use it just after the temperature drops below the limit will put it back over in short order.

    You're either running it harder than it was designed to be run or there's a faulty component or some part of the cooling system isn't doing its job (think blocked vent). Temperature sensors do go bad, but I wouldn't put it at the top of the list of suspects.
     
  8. gusfinley

    gusfinley Tele-Holic

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    There may be a thermal fuse inside the power transformer. If this trips, the only fix is to tear apart the transformer and replace or bridge the fuse.

    Something caused the protection device to trip in the first place, so you may have other issues.

    If you can jump across your overload circuit you might be able to find the primary problem.
     
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  9. schmee

    schmee Poster Extraordinaire

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    Hate those things. My bassist had an amp that would suddenly quit, 5 mins later it would start up again. Seems to me it's a band aid to fix a bad design.
     
  10. Blrfl

    Blrfl Tele-Holic

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    They're for safety, same as the mains fuse, because even good designs fail sometimes if the parts go bad.

    Most countries require that electrical gadgets be certified by a nationally-recognized testing agency like Underwriters Laboratories before they can be sold. Anything where thermal runaway could cause a fire (clothes dryer, space heater, powered speaker) won't pass without a cutoff.
     
  11. schmee

    schmee Poster Extraordinaire

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    Of course, one wonders why it's doing it though.
     
  12. robert donithan2

    robert donithan2 Tele-Meister

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    I thought either with or without power to place it in front of an air conditioner would maybe reset it?The refrigerator may be a bad idea...
     
  13. magicfingers99

    magicfingers99 Friend of Leo's

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    try putting a muffin fan in the cabinet. probably need to drill some cooling holes, if its out of warranty. it might be an engineered failure point to provide a consumer upgrade path, ie built in obsolence point.
     
  14. Blrfl

    Blrfl Tele-Holic

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    Blowing cold air on it will help dissipate the heat and will reset the cutoff. The AC would work; I'd avoid the 'fridge. Running an electric fan behind it would probably help, too, but you probably want more quiet than that while you're trying to listen. Might be worth the experiment just to see if it is actually the thermal cutoff and not some component that fails when it gets warm.

    One thing that hasn't come up: How hard are you running these things?
     
  15. robert donithan2

    robert donithan2 Tele-Meister

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    Not at all..I live in an apartment so no loudness...I have two of the same monitors and the other one has never cut off.
     
  16. Blrfl

    Blrfl Tele-Holic

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    So probably something's just had it then.
     
  17. robert donithan2

    robert donithan2 Tele-Meister

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    [​IMG]

    Robert Donithan

    I thought I'd ask someone after running all my tests, ask someone the cost of an average repair shop to look at it? And does, if the factory says they don't have parts ,will a repair shop be able to find parts?(are they pretty much interchangeable)
     
  18. Blrfl

    Blrfl Tele-Holic

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    In something like that, the parts are probably going to be off-the-shelf and easy to find. Really all that's in the box are a power supply and a couple of amplifier, none of which is rocket science.

    However...

    Without starting a discussion on our disposable society, for the $120 price tag on a new one, you'd probably be better off replacing it. Handing the flaky one to a shop with no access to schematics or a service manual means they're going to have to burn more labor to figure out how it works, diagnose it, then source the part(s) and do the repair.

    The down side, of course, is that if you want a matched pair, you'd have to get another MX-5 which could go south on you as well or your surviving good one might go, too. I'm not a big fan of powered speakers because the innards are constantly subjected to vibration and speakers and ventilation aren't always compatible.
     
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