What was found
ON TAKEOFF, AFTER GEAR RETRACTION, CAPTAIN'S AIRSPEED WENT TO ZERO & THE ALTITUDE WENT TO 50K. NO AUTO THROTTLES EVEN WITH GREEN LIGHT SWITCH ON. FLIGHT RETURNED TO FIELD AT PBI. AFTER LANDING, THE ALTITUDE IN WINDOW WENT TO 500 FEET. R & R FCC CHANNEL B & MODE CONTROL PANEL IAW AMM 22-11-33, PB401 & AMM 22-11-34, PB401. OPERATIONS CHECKED NORMAL, ACFT OK FOR SERVICE.