What was found
15 MIN FROM DESTINATION LEAVING 15000' WE LOST BOTH CAPTAIN'S & FLIGHT OFFICER'S FLIGHT DIRECTORS, AUTOPILOTS & AUTO THROTTLES DISENGAGED. WE RAN QRH & SWITCHED TO NR 1 DFGS. ALL SYS WERE NORMAL UNTIL WE GOT ONTO THE APPROACH. ABOUT 15 MILES OUT ON THE APPROACH WE AGAIN LOST BOTH FLIGHT DIRECTORS, FMA'S BOTH WENT BLANK, AUTOPILOT & AUTO THROTTLES CLICKED. VHF NR 1 SHOWED LOCALIZER COURSE TO THE LT VHF NR 2 LOCALIZER SHOWED COURSE TO THE RT. WE EXECUTED MISSED APPROACH TO GND 10 MIN FROM GND LT ACFT BUS SENSING CB POPPED. R & R DIGITAL FLIGHT GUIDANCE CONTROL PANEL IAW AMM 22-01-02. RTS NR 1 & NR 2 DFGC'S GO IAW AMM 22-01-05.