6550-23N/23S/33N/63N/63S/73N2-2. A AND D BOARDS REMOVAL2-3. SERVICE POSITION2-21 Screw(+BVTT 3 x 8)CN601GNDGND6 Three screws(+BVTT 3 x 12)7 Four screws(Washer head +P 3 x 8)2 Cable stopper5 A board8 D board3 Cable cover4 Cable holder12A boardD board3(Note) The electric potential of heat sink of IC401 is not GND.So please do not touch it absolutely to the base chassisand etc., which make an ultimate cause of the bad move-ment or break.