Hi i discovered the problem was that one of the Phillips tda1543 chips had died affecting both sides of the audio,even though there are 8 of them, 4 on each side .Through a process of elimination eg i removed one at a time until the distortion stopped i then replaced with new from ebay for £4. and its now working fine ,its a bit awkward getting access to the chips because they are underneath the printed circuit board that is separate from the surrounding pcb with some nuts and bolts going through to the chassis ,the chips have some contact adhesive on the top of them the nuts and bolts pull the upside down chips towards the chassis creating a heat sink ,care needs to be taken to pries the chips from the chassis prior to sliding the pcb out , then remove one at a time replace the pcb power up and check the sound ,as you remove each chip the output volume goes down ,you will notice when the faulty one is removed ,if this is the same fault as you have i hope this helps .I also got no reply from Kevin ,but not surprising as there is only about £20. profit in it for him .