What was found
AIRCRAFT GROUNDED. AMBER LE FLAP TRANSIT LIGHT AT FLAPS 15. FLIGHT CREWS ACCOMPLISHED QRH FOR LEADING EDGE FLAPS TRANSIT. REPLACED FLAP/SLAT ELECTRONICS UNIT (FSEU) IAW AMM 27-51-01/401. BITE AND OPS CHECK GOOD. NO DEFECTS NOTED. FURTHER TROUBLESHOOTING REMOVED AND REPLACED LE 1 SLAT INBOARD PROXIMITY SENSOR IAW AMM 27-88-11/401. OPS CHECK FAILED. LE 1 SLAT INDICATOR STILL FAIL INTERMITTENT. COMPLIED WITH FIM 27-81 TASK 803 AND REMOVED AND REPLACED FSEU IAW AMM 27-51-01/401. OPS CHECK FAILED WITH POWER SUPPLY FAULTS. PUT ORIGINAL FSEU BACK ON AIRCRAFT.