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Troubleshooting General/ Logic Board Troubleshooting - 18
DS4 and DS5 = USB power for downstream devices
DS5 = USB port 1- lower
DS4 = USB port 2- upper
(There is no DS2 or DS3 on the board.)
When illuminated, these LEDs indicate that the computer is
providing power (+5 V) to downstream USB ports. USB devices do
not need to be connected in order for these LEDs to illuminate.
However, if one or both of the LEDs is not illuminated and a USB
device is/was attached (and the system has completed its boot
process), then the logic board has removed downstream power
because of a trouble condition.
Since the downstream power is controlled individually for each
port, it is possible to have these LEDs in a different state: one off
and one on. This way if one port has troubled USB devices, the