How fast is the standby light flashing? Slow, around once a second, usually means power supply is broken. Check and replace broken fuse(s). If all fuses are OK then also check small value resistor that sets/isolates the analog ground path to earth. Fast, 3 times a second, usually means power supply is ok but the amps are drawing too much current due to short(s).
Answers & Comments
How fast is the standby light flashing?
Slow, around once a second, usually means power supply is broken. Check and replace broken fuse(s). If all fuses are OK then also check small value resistor that sets/isolates the analog ground path to earth.
Fast, 3 times a second, usually means power supply is ok but the amps are drawing too much current due to short(s).
That is what Id check first.
Or faulty amp circuit.