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81 Music Man Repair - 6L6 Installed Wrong

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  • 81 Music Man Repair - 6L6 Installed Wrong

    Hey forum! I recently acquired an 81 Music Man 112 RD (100w) that does not work or turn on. After opening it up, i noticed the large 470 resistor attached to pin 6&4 of the power tube was cooked. That combined with a tube that has a broken key led me to one conclusion - someone installed the tube wrong agter the key broke off.

    My question is, assuming this isnt the first time this ever happened, should i expect this repair will only be confined to the resistor and tube or can i expect something else to have cooked that I dont see (i.e. a transformer or something)?

    Click image for larger version

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    Click image for larger version

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  • #2
    You'll have to fix it and find out.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Originally posted by Jtwusmc View Post
      should i expect this repair will only be confined to the resistor and tube or can i expect something else to have cooked that I dont see (i.e. a transformer or something)?
      Depends whether you are an optimist or a pessimist . Sometimes it's just the resistor and tube, maybe also a hum balance pot or heater circuit resistor. But if someone overfused it after the original fuse blew, all bets are off.
      Like Enzo said, only one way to find out.
      Remove the bad tube, replace the blown fuse and see if it runs. It doesn't need all the power tubes in for testing purposes.
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


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      • #4
        And I don't know about this one, but many Music Man amps are cathode driven, so those cathode transistors may be damaged too.
        Education is what you're left with after you have forgotten what you have learned.

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        • #5
          Thanks for all the inout everyone! Ill start with fixing the resistor and see where ittakes ne. One last question. From the pic above, is that a 2 or 5 watt 470 resistor?

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          • #6
            2w is fine. it is just a screen resistor.
            Education is what you're left with after you have forgotten what you have learned.

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