Pioneer SX-1250 weak left channel any suggestion on where to fix?

[PooPoo]

Got a pioneer SX 1250 that has a weak left channel that I really want to fix I've cleaned the switches and buttons with de oxit really well no scratchy noise so it's not dirty switch issue? Maybe a transistor somewhere? Need some Help please?

 

[markthefixer]

get a pair of cables, pull the pre-out and amp in jumpers and cross wire (L>R, R>L) the pre-out and amp in plugs with them, if that channel stays weak it's the power amp