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Mesa Boogie Big Block 750 fuses / Service lit

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  • Mesa Boogie Big Block 750 fuses / Service lit

    Hey folks,
    Does anyone know what the value of the HT fuses in this amp? The prev tech put in 15A 32V car fuses. I'd like to get the correct 3AG fuses, but I'm not certain he got the amperage right. 15Amp sounds about right for this amp, but there's no indication in the amp as to the proper value.
    Also a schemo would be nice.
    I tried contacting Mesa, but I'm told they're all out 'surfing' on Friday's (;- )
    Thanx, Glen

  • #2
    If they are HT fuses, 15A sounds kinda big?
    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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    • #3
      Whoops, if that 'HT' is in a solid-state rather than tube context, ignore what I said.
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


      Comment


      • #4
        The owner's manual shows 15A Slow Blow on the back of the unit.

        Click image for larger version

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        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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        • #5
          Hey Dude,
          these HT fuses are internal mounted on the PCB. Since we're now Mesa authorized, I was able to get the serv lit & see that the value of those HT fuses were. As it turns out, they are also 15A SB 3ag fuses!
          tAlso, The amp had 4.5V offset on the pre-relay side of the power amp keeping it in protection. Since this amp had been messed with previously, I was looking for something he did. I found 2ea 390K resistors that were apparently a bias mod at the factory which had been unsoldered. I have no idea what issues the previous tech was having, but I merely resoldered those resistors & the offset was gone & the amp functioned.
          Thanx man....Glen

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