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HELP Peavey XR684 XLR x5 mic i/ps dead! Precedented fault?

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  • #1

    HELP Peavey XR684 XLR x5 mic i/ps dead! Precedented fault?

    Hi,
    I have seen a lot of pa gear but never this degree of i/p failur.
    It must be a design flaw/weakness.
    A quick look at the schematic makes me think one of the 2 pre amp 1N1485s has blown.
    I noticed a post to which a guy knowledgable on these responded and maybe he or others know of this weak point and its solution.
    Chrs.
    Tags: None
  • #2
    This is a common design, I really doubt there is a design flaw behind one channel failure. This is a basic differential input into an op amp.

    What is wrong with the mixer, you didn;t tell us?

    Your diodes in the input circuit are 1N4148, not 1N1485. There is a letter "S" at the end that looks like a 5. so 1N4148S. But any common 1N4148 will do fine.

    Unless you removed the diode for testing, since it is in parallel with a transistor, it would be difficult to determine which part was bad if one of them was shorted.


    Most common problem with these mixers is people breaking off the XLR connectors.

    What is wrong? XLR not working, 1/4" jack not working? Both not working?
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Hi Enzo,
      Sorry I forgot your name.
      I did say....HELP Peavey XR684 XLR x5 mic i/ps dead! Precedented fault?

      Hi,
      I have seen a lot of pa gear but never this degree of i/p failure.

      Line in fine.
      Strange that 1/3/5 are okay.

      i/p trs seem okak.
      I am looking at electrolytics in line from XLR to tr. bases.

      I nneded to repair speedily and first thing I did was resolder LR pins.
      Crisis past now, but still not fixed.
      Thanks for any help.
      chrs.

      Comment

      • #4
        Hi again,
        Sorry, I have been giving this my divided attention. I meant the 2SD1484K trs, not the diodes.
        I somehow missed some of your post.
        I tried A-B comparison disturbance tests around the pre-amps. looking for disparities.
        I really need to knock up a signal injector.
        All line inputs ok but XLRs chans 1-3-5 dead.
        I suppose they must have been overloaded by the previous owner.
        I hope it's not the m. surface mounts at fault.
        Why is there an electrolytic in series with signal path?
        chrs.

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        • #5
          Hi,
          Fixed it.
          Sorted.

          Comment

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