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Thread: Fender Stage 100 DSP **** P R O B L E M ****

  1. #1
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    Fender Stage 100 DSP **** P R O B L E M ****

    I need help!

    My amp is broken.

    The electronics I know something so I can to finish the job alone,
    but I need instructions about what can be a defect and how to fix it.

    Symptoms:
    - Very noise in the speaker
    - Mechanical damage to the parts you see in the photo
    Attached Thumbnails Attached Thumbnails 44.jpg   33.jpg   22.jpg  

  2. #2
    Noodle of Reality Steve Conner's Avatar
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    Looks like your output stage had a meltdown!

    Do you know what a transistor is, and how to test one?
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

  3. #3
    Supporting Member Jazz P Bass's Avatar
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    Yeah, the circuit that you indicate is the "protect" circuit.
    If that is bad, there are most assuredly other issues.

  4. #4
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    I know a lot about electronics.
    I did never repaired amplifiers, But before I made ​​some other devices so that I know the basics.

    I suppose that the amplifier is turned on without speakers and that is the reason for this failure.????

    First I need to replace the two transistors what are damaged?

    So I should check the output transistors?

    Stage100_Stage100H_Stage160_schematic.pdf

    This is the original scheme of the amplifier

    Thanks

  5. #5
    Old Timer
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    Those visibly burnt transistors are a symptom but not the original cause.
    Check Q10 to Q19 for shorts, all 0.47 ohm ballast resistors, and any diode you find there, just for starters.
    Google "lamp bulb limiter" and build one.
    Good luck.

  6. #6
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    Ok.
    One question.
    These parts, which you listed how to check in?

    Do I have to remove the parts and check in (I know to do it)
    or
    Is there a way to be checked without removing?


    P.S.
    I have a lot of measuring instruments and tools

  7. #7
    Supporting Member Jazz P Bass's Avatar
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    It will not "hurt" the amplifier to operate it without a load (speaker).
    Keep in mind that the output section uses a grounded emitter.
    The current to drive the speaker comes "from" the power transformer windings.
    "This is not your dad's Oldsmobile"

  8. #8
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    Hahaha ...
    I know that.
    I bought this amp broken.
    The seller said that it is a input jack and that noise comes from broken input jack.

    I got a good price and it is the reason why I bought this amplifier

  9. #9
    Supporting Member Jazz P Bass's Avatar
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    Quote Originally Posted by colmax View Post
    Ok.
    One question.
    These parts, which you listed how to check in?

    Do I have to remove the parts and check in (I know to do it)
    or
    Is there a way to be checked without removing?


    P.S.
    I have a lot of measuring instruments and tools
    You can have all of the test equipment & measurement tools in the world but they will not help you repair this amplifier.
    What you need, in this case, is a familiarity with solid state output sections.
    If you do not have that, the repair will rely on a hit or miss approach.
    I would not recommend that to anyone.
    Sounds to me as if you really should take the equipment to a tech.

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