Rc-300 power schematic

[Locrian]

Hello,

I was hoping someone here may have some information on this.  I have a boss rc-300 looper that is not powering on.  I have gone through with a multimeter and can see that power is getting to the switch the back to pins.  When the switch is pushed these go to 0v, it appears the middle pins are ground on the switch as there is continuity between them and pin 4 on the 4580 ic's on the board.    I suspect someone plugged the wrong power supply in and toasted a diode or something.  But without a schematic I'm worried this is going to be beyond my ability to find in this mess of smd components.  I have a new switch coming, while I'm waiting for that to arrive I was hoping someone here might have some suggestions on places to look (know where the polarity protection diode on the board is etc).  Any help would be greatly appreciated.  Thank you.