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Thread: Line 6 MM4

  1. #1
    Supporting Member Jazz P Bass's Avatar
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    Line 6 MM4

    Had a Line 6 MM4 come in.
    Would not power on.

    Checked all of the voltages, which where good.
    3.3Vdc came up when a cord was inserted into the input jack.
    Pressing any key did nothing.
    Tried a master reset at power On (Hold A and D keys down, power On)
    Nothing doing.
    Scoped the crystal. Oscillating fine.
    OK. Now what.

    I used a 10X magiifier a looked at the main microcontroller.
    Some of the solder pads looked iffy at best.
    So I hit it with my Weller 750 degree heat gun and then popped it in the freezer for 10 minutes.

    Lo and behold!
    It works.

    Thought I would pass this on.)

    Here is a voltage measurement schematic.
    And a brief of how the power supply functions from a gentleman in Scandinavia.
    Attached Files Attached Files
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  2. #2
    g1
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    don't forget the joker g1's Avatar
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    Is the freezer part some trick or just so you can handle it?
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    Certified Dotard

  3. #3
    Supporting Member Jazz P Bass's Avatar
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    More than anything, I wanted to make sure the core of the ic was cooled down.
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  4. #4
    Supporting Member Jazz P Bass's Avatar
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    Well, after 3 hours running , it locked up.

    Pulled the Eprom out & gave the pins a quick wipe with DeOxit.

    Now it's working again.

    Stay tuned.

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