Latest amp in the workshop is this Plinius 8150. If you look at the photos you can see that there has been quite a severe short circuit in the amp, leaving a charred section of the circuit board, and a black mark on the top of the case. The amp was also oscillating badly. On disconnecting the pre section the oscillation stops so it looks like the cause is the damaged preamp section. Damaged resistors and capacitors will be replaced and everything else checked over.