Question for the amp pro's (need help w/ question)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Mooncusser, Jul 27, 2006.

  1. Mooncusser

    Mooncusser Member

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    Hi Guys/Gals,

    I was wondering if I could ask a quick question.
    I have a Marshall 1959 SLP RI.
    If I were to buy the applicable model Weber Bias- rite, how would that work out for me in aiding the bias procedure?.
    If I understand correctly, you insert the testers into the tube sockets, and you will have a reading on the display box that is included in the kit, BUT,
    wouldn't you still have to pull the amp out of the head cab to then access the bias adjustment componet?

    In other words, you can't adjust the bias just by using the Weber kit, right? The Weber kit is just a way to view the tubes current readings?
    Please correct me if I am wrong.
    Thanks so much for the help with this question,
    Mass
     
  2. Blue Strat

    Blue Strat Member

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    Yes, the "bias adjustment pot", if like most other Marshall amps, is accessible only from inside the cabinet. It's mounted on the circuit board.

    In some amps, Fenders mainly, the bias pot is located under the chassis and is accessible from both inside and outside of the amp.

    In any case, the amp must have a bias pot and you must physically adjust it.
     
  3. Mooncusser

    Mooncusser Member

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    Would you happen to know where on a 1959 SLP RI the bias pot adjustment is? on the top or bottom?
    Thanks for your time once again,
    Mass
     
  4. Blue Strat

    Blue Strat Member

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    It's inside. In every Marshall I've looked at, it's mounted to the circuit board near the power tube end of the board. It's a small "trim pot".
     
  5. Mooncusser

    Mooncusser Member

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    So in my case with the 1959 SLP, I would have to remove the amp housing from the chasis (head cab) and then turn the actual metal housing upside down to access it the trim pot?
    you guys are a great help and thank you.
    Take care,
    Mass
     

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