Although the main caps (purple) on these amps can blow very spectacularly, they also go dead short with no other signs of failure.
Check Q703 and Q702 which are thyristors that are mounted to the heatsinks at the bottom left of your second picture. If a cap is short then one of them is likely to have blown its top off.
Also, as itchy said, check underneath for blown printed circuit track.
Cheers. (at least 1 or 2 good answers in here )
I have sent it off for repair earlier but will check the back of the board when its returned to check for brown burn marks and Q703 & Q702.