A question for the fx building/modding folks

The jack has three connector tabs in back. One is for - and the other two are for +. The two + are connected by a switch inside the jack, so when you plug a power supply plug into the jack it "breaks" the connection between them. The idea is that the + from the battery normally passes through there, but the connection to the battery is cut off when you plug in the adapter. So solder the - tab to the common ground inside the pedal, and solder one of the + tabs to the battery's + wire, and wire the other + tab to the point on the circuitboard where the battery's + wire used to connect.

I always get confused about which + tab is which, so use a multimeter to figure that part out.

 

Same here.