Has "USB drawing to much power" error. Trying to repair my mother board. Can only find service manuals with flow chart diagrams that lead to replace motherboard solution. Far from helpful. Can anyone point me in right direction. Tried resetting SMC and PRAM to no avail. SMC shutting down ports. Neither port working. Having difficulty tracing circuit and IC's difficult to identify. NEED SCHEMATICS. I think this is fairly common failure and will post solution if someone can assist. TIA ---------- Please consider I am electronic tech but know nothing of macbooks until yesterday so go easy.