GK MB Fusion tubes change

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


  1. Gorriot

    Gorriot

    Joined:
    Nov 26, 2013
    Messages:
    4
    Location:
    Lille (France)
    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 Gold Supporting Member

    Joined:
    Nov 21, 2008
    Messages:
    16,885
    Location:
    Lake Havasu City, Az USA
    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

    Joined:
    Mar 6, 2012
    Messages:
    2,617
    Location:
    New Jersey
    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

    Joined:
    Nov 26, 2013
    Messages:
    4
    Location:
    Lille (France)
    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. Register to disable this ad
  6. Bassmec

    Bassmec

    Joined:
    May 9, 2008
    Messages:
    3,187
    Location:
    Ipswich UK
    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!"
     
  7. Gorriot

    Gorriot

    Joined:
    Nov 26, 2013
    Messages:
    4
    Location:
    Lille (France)
    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 !
     
  8. B-string

    B-string Gold Supporting Member

    Joined:
    Nov 21, 2008
    Messages:
    16,885
    Location:
    Lake Havasu City, Az USA
    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.
     
  9. Bassmec

    Bassmec

    Joined:
    May 9, 2008
    Messages:
    3,187
    Location:
    Ipswich UK
    Disclosures:
    Proprietor Springvale Studios
    Have fun I bet you will end up with the Philips branded tube in V1.:bassist:
     

Share This Page