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

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