What was found
AT APPROX 35-40 KIAS, THE T/O WARN HORN SOUNDED. ABORTED THE T/O. THE CONFIGURATION WAS NORMAL AND PROPER. RETURNED TO GATE. CLEANED AND LUBRICATED PARKING BRAKE MICROSWITCH. C/W OPS TEST OF THE TAKEOFF WARNING SYS IAW AMM TASK 31-41-00-710-802. OPS TEST IS GOOD. GROUND RAN A/C IN TAKEOFF CONFIGURATION AT 55 PERCENT TORQUE WITH FLAPS AT 5, 10 , AND 15 DEGREES. NO DEFECTS NOTED. RETURNED TO SERVICE. NO PARTS REPLACED.