What was found
PHX - AIR TURNBACK, AFTER TAKEOFF THE FLAPS WERE RETRACTED BUT L/E FLAPS TRANSIT LIGHT ON FORWARD PANEL AND NR 1 SLAT INDICATOR ON THE OVERHEAD PANEL REMAINED ILLUMINATED. FLAPS WERE CYCLED BACK TO 1 & THEN UP SEVERAL TIMES. PILOT VISUALLY CONFIRMED THAT NR 1 SLAT WAS STILL EXTENDED APPROX 1.5 INCH; THIS WAS THE CASE ON EACH TRY. THE AIRCRAFT RETURNED TO PHX MAKING AN UNEVENTFUL LANDING. IN PHX MAINTENANCE TROUBLESHOT AND CONFIRMED THE SLAT ACTUATOR WOULDN''''T FULLY RETRACT. THE NR 1 ACTUATOR WAS REPLACED AND ALL FUNCTIONAL CHECKS WERE GOOD.