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My marshall b30 bass amp switches on but doesn't produce any sound?

it produces a quiet crackling noise from inside near the input socket. It has had this problem before and for no apparent reason has manged to work again weeks or months after assuming it was completly broken. It can still function through the headphones jack but nothing come out of the speaker.
Max Tarneberg, November 2005
headfone socket switch is probably dirty if headfone plug disconects the speaker. look at plug and see if a leaf spring switch is being used - apply some switch cleaning fluid to fix.

headfone is probably conected across speaker with resistor in series - ie, the amp still works. check speaker resistance (approx 8 ohms) and wiring.

fiddles, November 2005