XO Troubleshooting USB

This is the portion of the XO Troubleshooting Guide for diagnosing problems with the USB interfaces of an XO laptop.

One of the USB ports doesn't work

This is typically due to broken connector or solder joint at the affected connector.

All of the USB ports receive power from a common switch, so if there is a problem with power it is likely due to a broken connector or solder joint at the connector.

The USB signals run directly from the connectors to the CS5336 Southbridge. If there is a signal integrity problem, and it is not at the connector, the motherboard must be replaced.

There is no repair for this motherboard

None of the USB ports work

If none of the USB ports on a laptop work, even after re-installing the software, then the motherboard needs to be replaced.

Measure the +5V supply at the USB connector (or across C509 or C551). If it is not present, the USB power switch and current limiter, U56, may be broken. It may be bypassed by a 0 ohm resistor at R466 for testing purposes. If the audio (speakers) is also non-functional, that verifies that the problem is the +5V supply on the motherboard.

Motherboard signal integrity

The hardware self-test provided by Open Firmware contain a section where test signals for the USB ports are output, allowing signal integrity (eye diagrams) to be made using an oscilloscope.