thank you, are they replaceable? is it easy? any idea on cost? Many thanks and happy Christmas

I have three questions if anyone can help me please.... One of my Penta Lab Ones 6602 serial number 05207700 (- the tall hexagon ones with built in active power amps at the bottom) has started humming all the time that it is playing music, it also thumps on start up and has to be put to sleep manually with the switch on the front...what has gone wrong