8 chassis intrusion switch, 9 speaker, 10 heat sink and processor – Dell OptiPlex 390 (Mid 2011) User Manual
Page 4: 11 coin-cell battery, 12 power switch cable, 13 system fan, 14 input/output panel, 15 power supply

8 Chassis Intrusion Switch........................................................................23
Removing the Chassis Intrusion Switch
..........................................................................23
Installing The Intrusion Switch
.......................................................................................24
.......................................................................................25
10 Heat Sink And Processor......................................................................27
Removing the Heat Sink and Processor
..........................................................................27
Installing The Heat Sink And Processor
.........................................................................30
Removing the Coin-Cell Battery
......................................................................................31
Installing The Coin-Cell Battery
.......................................................................................32
Removing the Power-Switch Cable
................................................................................33
Installing The Power Switch Cable
.................................................................................34
...............................................................................................35
...............................................................................................36
Removing The Input/Output (I/O) Panel
...........................................................................37
Installing The Input/Output (I/O) Panel
............................................................................39
...........................................................................................41
...........................................................................................43