Dell P2421D Service Manual page 13

Tear off 2 pieces of aluminum foil. Use a
Philips-head screwdriver to remove 2 screws
for unlocking the mainframe
S7
(No.1~2 Screw size=M3x4, Torque: 3± 0.5kgf.cm)
Use a Philips-head screwdriver to remove 7
screws for unlocking the main board and the
adapter board
S8
(No.1~7 screw size=D3x6, Torque: 6± 1kgf.cm)
(No.9 screw size=M4x6, Torque: 6± 1kgf.cm)
Disconnect all of the cables to separate the
S9
power board and main board.
Hold the plastic button on the power board to
S10
separate the Mylar from the power board.
The Mainframe
Use a Philips-head screwdriver to remove 3 screws
for unlocking the bezel and the middle frame.
S11
(No.1~3 screw size=M2X2.5, Torque: 6± 1kgf.cm)
13