What was found
CREW PERFORMED "PRIOR TO TAXI" CHECKLIST AND DISCOVERED FLAPS WERE STUCK BETWEEN 15 - 20 DEGREES. SHUTDOWN ACFT. MAINTENANCE TROUBLESHOT DISCREPANCY TO A DEFECTIVE LT FLAP CONTROL POSITION RESOLVER. ABLE TO DRIVE THE FLAPS ALL THE WAY UP TO 0 DEGREES USING THE "BREAKOUT BOX" THAT WAS USED IN TROUBLESHOOTING. CREW FLEW ACFT BACK TO HOME BASE USING THE "LANDING WITH FLAPS UP OR AT 7 DEGREE POSITION" PROCEDURES. ON ARRIVAL, LT FLAP CONTROL POSITION RESOLVER REPLACED, OPS CHECK OF FLAP SYSTEM WAS GOOD, AND ACFT RELEASED BACK TO SERVICE.