Marshall 9005 blowing fuses one side.

Discussion in 'The Workbench' started by Neale Dunham, Jan 22, 2021.

  1. Neale Dunham

    Neale Dunham New Member

    Apr 22, 2018
    Likes Received:
    Hi guys anyone got any ideas on this one?

    So, I got a Marshall 9005 the blackface 3u monster.

    Its a dual bloc amp

    The right hand side works fine but the left takes out the T5 fuse every time.

    I swapped the valves from the left to the right and all works well so I guess I can eliminate valve failure at least.

    Ive also checked the circuit board underneath and can see nothing obvious like dry solder or burnt resistors etc.

    What does that leave me with?

    O/T failure or capacitors perhaps?

    I'm not sure which way to take it?

    If anyone has had similar issues with this amp or maybe knows a thing or two please shout up.

    Many Thanks.
  2. johan.b

    johan.b Well-Known Member

    Feb 21, 2015
    Likes Received:
    Södertälje, Sweden
    Here is a link to the schematic

    Sounds like a diode failure more than a cap or tranny to me

    tell us more how the failure happened... any symptoms before failure? Does it blow the fuse without tubes installed too?
    Last edited: Jan 23, 2021
    Gunner64 and neikeel like this.

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