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GK MB Fusion tubes change

Discussion in 'Amps [BG]' started by Gorriot, Dec 11, 2013.

  1. Gorriot

    Gorriot

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    Hi everyone,

    Hope I post in the right section.

    I am about to change the tubes of my MB Fusion but, before put my hands in it I know I have to discharge capacitors. I found on the web some technics to do that and I think I understood it but the problem to me right now is on which part of the capacitor I put my little tool going to earth to discharge ?

    I saw videos where things are clear but do you guys already opened a MB Fusion ? And if so how did you discharge, and did you discharge all the capacitors or which one is the one to discharge in priority.

    I am not even thinking of how will I pull the tubes for now, one problem after one !

    Thanks for reading and eventually replying.
  2. B-string

    B-string Supporting Member

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    The MB Fusion uses a SMPS not a line frequency power supply. Just don't touch the board with the big caps if you can avoid it.
  3. BawanaRik

    BawanaRik Supporting Member

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    On older amps leaving the speakers plugged in and removing the power cord with the amp all on will usually drain the caps.

    This new stuff who knows.

    Check pin 1 or 6 if it's a 12ax7 for voltage to be safe.

    Use a meter.
  4. Gorriot

    Gorriot

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    Thanks for your quick reply B-String, tubes are on the left and the big capacitors are on a board on the right, I think I will be safe.

    And I will use BwanaRik technic too... will be more than safe !

    Great community here, helped me choose my amp more than one year ago, now help with tubes... thanks.
  5. Bassmec

    Bassmec

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    Disclosures:
    Proprietor Springvale Studios
    These are very, very, very good tubes, if you can get them off eBay for reasonable money get them:
    [​IMG]

    They are not made anymore but old ones will last ages and sound fabulous just as good as telefunken but Mullards :hyper: they are built to the same military spec as RCA JAN 12ax7.:bassist:
    "Don't be a Dullard! Fit a Mullard!"
  6. Gorriot

    Gorriot

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    I did some research about tubes past weeks... discovered a world ! Was not really suspecting how important a tube could be.

    I saw old Mullards but expensive and I had to make a choice between lots of pieces !

    So,

    I bought a Tungsram from 1974. A Philips branded Miniwatt from Holland, 1960 and a Ei branded RSD (smooth long plates) from 1970.

    Will have to try different combinations I think... good time is coming !
  7. B-string

    B-string Supporting Member

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    Your most noteable difference will come from the tube in V1 position. I would not "waste" an old world production tube in V2 or V3. Just my opinion.
  8. Bassmec

    Bassmec

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    Disclosures:
    Proprietor Springvale Studios
    Have fun I bet you will end up with the Philips branded tube in V1.:bassist:

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