Two things you did wrong.
12v - while the system handle 12v, its rated for 9 (though can run on as little as 7.8v) meaning its voltage regulator is wasting ~3v as heat
I also strongly suspect you incorrectly fed the SFC the complete wrong polarity. Like the Famicom, the Super Famicom requires 9v DC with a polarity of center pin negative.
Like this:
+ ---C--- -
NOT
- ---C--- +
You blew the 7805 voltage regulator by feeding it the wrong polarity. Open the system and replace that, and then make sure you only ever use the proper power supply.