What was found
ONCE CLEARED FOR TAKEOFF (8L) ADVANCED POWER LEVERS AND RECEIVED TAKEOFF WARNING HORN. ABORTED TAKEOFF AND ADVISED ATC. ALLOWED AIRCRAFT TO HOLD ON ALPHA TAXIWAY TO TROUBLESHOOT PROBLEM. CREW CONFIRMED FLAPS WERE SET AT 5 DEGREES BUT INDICATOR WAS A HAIRLINE ABOVE 5 DEGRESS. CYCLED FLAPS FROM 5 DEGREES DOWN TO 15 DEGREES THEN BACK UP TO 5 DEGREES. ADVANCED POWER LEVERS FORWARD TO TEST SYSTEM. TESTED OK. REQUEST TO TOWER, FLAPS WERE READING OUT OF 5 DEGREES AND WOULD LIKE ANOTHER TAKEOFF. TAKEOFF WENT WELL WITH NO PROBLEMS.