I am currently troubleshooting a single port in a two-port USB 2.0 bracket (example here) that does not work. A USB bracket is a simple device (consisting only of cables and connectors) that connects the pins of a USB header (on the motherboard) to two external USB ports.
The symptoms of the problem are as follows:
- It is only a single port of a two-port bracket that does not work.
- Whenever a keyboard or mouse is plugged into the port, it is only working once. That is, if I unplug then re-plug it, it is not detected until I reset the computer. None of these happened if I plug them into the other port.
- Whenever any other, more complex device is plugged into the port, they are behaving differently yet none of them is detected. When I plug a bus-powered external drive, the power light goes on and the drive spins. When I plug a cell phone, the phone connects briefly then disconnects. None of these happened if I plug them into the other port.
- Inside Windows, although the device is not detected, Windows is playing "Device Disconnect" sound when a device is connected, and playing "Device Connect" sound and showing a "USB Device Not Recognized" balloon when a device is disconnected.
- All the above symptoms also happen both in BIOS/POST and inside Windows (not detected = not shown in POST device list = not working in UEFI BIOS setup).
The troubleshooting steps I've taken are as follows:
- First, I am certain that it is the bracket (not the motherboard) that is having problem because no matter to which header I plug the bracket, it is always the same port in the bracket that is having problem.
- I've done continuity tests between both external ports' pins and the bracket connector's pins and they are all good (all less than 1 Ω).
- [Update #1] I've done continuity tests between all pins of the bracket, and found that the two Vcc pins are shorted to each other, and the two GND pins are also shorted to each other. All shorted pins' resistance are less than 1 Ω, everything else is "OL".
So, what could the problem possibly be? As the USB bracket is a custom part deep inside an old computer case, if at all possible I want to repair instead of replacing it.