I'll guess you mean S-Master Pro, which was a Sony digital amplifier technology from many years ago. I think the actual model number of the receiver doesn't matter in this case, we know we are dealing with a digital amp (unless you got this completely wrong).

In every owner's manual (and just common sense) you NEVER hook things up while it is on. You make all your connections, then check everything, then turn on.
Obviously someone screwed up and touched a wire somewhere or together. Although there are protection circuits, they don't always work.

The only thing you can do is pull the power cord from the Sony. Leave it unplugging for at least 10 minutes, then plug it back in and see if it reset.
If not, then whoever did this blew the amp and it now needs repair or replacement.
Hard lesson learned.