What was found
AT GATE PRIOR TO PUSHBACK, SMELL OF SMOKE IN FLIGHT DECK. EXTERNAL AIR WAS POWERED OFF. APU BLEED AIR WAS ON. F/A REPORTED NO SMOKE SCENT IN CABIN, ONLY FLIGHT DECK. CORRECTIVE ACTION: T/S R & R STATIC INVERTER, PER AMM A321 25-18. PERFORMED WIRING CHECKS BETWEEN 3NA AND CA/FO ELECTRIC OUTLETS, INTEGRETY CHECKS GOOD.