What was found
NO TAKEOFF LIGHT AND HORN CAME ON AT TAKEOFF POWER AND TAKEOFF ROLL INITIATION. FLAPS 15, SPEED BRAKE RETRACTED, TRIMS SET FOR T/O). FOUND RT SPEED BRAKE SWITCH JAM NUT BEING PUSHED UP BY SPEED BRAKE DOOR SUPPORT BRACKET, CAUSING PLUNGER TO RELAX. ADJUSTED SPEED BRAKE SWITCHES, RAN A/C AND CYCLED SPEED BRAKES, FLAPS AND TRIM FOR 1 HOUR, NO FAULTS NOTED IAW CE560XL MM 27-61-00.