Dell P2421DC Service Manual page 15

S7
Tear out all the cable to remove the rear cover and
put it on a protective cushion. Use a Philips-head
screwdriver to remove 10 screws for unlocking
the middle plastic bezel with the whole unit, and
then remove the middle plastic bezel carefully.
(No.1~20 screw size=M3x4, Torque=3± 0.5kgfxcm)
Remove the mylar by hand and Use a
Philips-head screwdriver to remove 9 screws for
unlocking the main board and the adapter board
S8
(No.1~9 screw size=D3x6, Torque: 6± 1kgf.cm)
S9
Disconnect all of the cables to separate the
power board and main board.
The main board
The Mainframe
15