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  • What are these?

    I'm in the middle of a QSC MX2000a which I'm hoping I can get the parts I need for it.
    In the event that they aren't I've been reversing this board that has 1 blown SOT-23 transistor on it. I have most all the parts figured out but there are 3 clearish what looks like a SOT-23 transistor that has no part numbers.
    Any guess guys?
    Click image for larger version

Name:	U901-MX200a-QSC-sm.jpg
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    Possible schematic
    IC-00008-00_RevC-Schematic.pdf
    Last edited by Techknowman; 09-16-2010, 03:47 AM.

  • #2
    NO idea. Got a good one from the other channel? If you can identify PNP vs NPN, then make an educated guess. My suspicion is none of them are darlingtons, so basic bipolars, and consider the voltages they face. SO my first reaction would be SOT versions of MPSA42/92 or MPSA43/93.

    Are all three terminals used? Or are two terminals shorted? WOndering if they could be LEDs, the three leg package being for stability. LEDs for their voltage drops, not as indicators. ANything lighting up on the good channel one?

    The amp schematic doesn't delineate those things. The little boards are replaced as a component. Fixing them is so very old school. I'll look and see if any of my documentation covers the innards of those.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Some of those are diodes in a SOT package. the clear parts have 2 of the pins on one side tied togeather, so they may be leds im going to check

      Comment


      • #4
        LIB MR LEDS
        Red LEDs to be exact! Well 2 of them are.
        The middle one reads like a diode /led but doesn't iluminate.

        On the original post I included the reversed schematic i have at this point
        Last edited by Techknowman; 09-16-2010, 03:48 AM.

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