What was found
(CAN) PILOT REPORTED SMOKE COMING FROM UNDER COPILOTS SEAT, WITH BATTERY SWITCHED OFF AND MASTER REFUEL PANEL POWERED ON. MASTER REFUEL VALVE WAS OPEN, MAIN FUEL VALVES WERE OPEN. OCCURENCE OCCURED WHILE ACFT WAS PARKED ON GROUND. MX ACTION REMOVED SHORTED DIODES CR9 AND CR10 AND INSTALLED NEW DIODES P/N 132408-8 AT PANEL DA SUBPANEL J. INSTALLED NEW FUSE P/N 5920-99-012-0080 ON ZL PANEL, F23 LOCATION FOR REFUEL PANEL. OPS CHECKED SATISFACTORY IAW MM, CHAPTER 28-22-00.