Dell OptiPlex 990 Mini-Tower Service Manual page 94

Controls and Lights
Back of the computer:
Link integrity light on integrated
network adapter
Network activity light on integrated
network adapter
Power supply diagnostic light
94
see the Service Manual at
support.dell.com/manuals.
Green — a good 10 Mbps
connection exists between the
network and the computer.
Orange — a good 100 Mbps
connection exists between the
network and the computer.
Yellow — a good 1000 Mbps
connection exists between the
network and the computer.
Off (no light) — the computer is not
detecting a physical connection to
the network.
Yellow light — A blinking yellow
light indicates that network activity
is present.
Green light — The power supply is
turned on and is functional. The
power cable must be connected to
the power connector (at the back
of the computer) and the electrical
outlet.
NOTE: You can test the health
of the power system by
pressing the test button. When
the system power supply
voltage is within specification,
the self-test LED lights up. If the
LED does not light up, the
power supply may be defective.
AC power must be connected
during this test.