Several USB ports on my PC have gradually stopped working properly with devices that draw more power, including two USB Wi-Fi adapters and an Xbox controller cable. Low-power devices such as my mouse, keyboard, and a flash drive still work on many of the same ports. When I connect the Wi-Fi adapters or controller, Windows repeatedly refreshes Device Manager as though the device is connecting and disconnecting. Both Wi-Fi adapters work normally on another computer, so the devices themselves appear to be fine. I tested the rear motherboard ports, including USB 2.0 and USB 3.x ports. Two USB 2.0 ports do not recognize the flash drive, although they still operate the mouse. My system uses an MSI MAG A550BN 550W power supply and an MSI B450M PRO-VDH MAX motherboard. Could this be insufficient USB power, a failing PSU, a motherboard or USB-controller problem, or a Windows/driver issue? What tests can distinguish these causes, preferably without specialized equipment?
2 Answers
The symptoms could be caused by unstable USB power, but they do not automatically mean the entire power supply is failing. USB devices use the PSU's 5 V output through the motherboard, and a fault in the motherboard's USB power circuitry or controller could affect several ports while leaving low-power devices functional. A USB power meter, a known-good powered USB hub, or testing from another operating system can help separate a power or hardware problem from a Windows driver issue. If the behavior is the same outside Windows and the port voltage is unstable, focus on the motherboard or PSU rather than drivers.
A USB power meter would be a useful first check because it can show the port voltage and current while a device is connected. If the voltage drops or the device keeps resetting, that points toward a USB power-delivery problem. Since these are rear motherboard ports, a case cable is less likely to be responsible. If the USB readings look normal, the motherboard or its USB controller becomes a stronger suspect. A PSU tester can also check the supply's output, although a failing PSU is only one possible cause.
I tested every rear port and found that both Wi-Fi adapters and the controller repeatedly connect and disconnect, while the mouse and keyboard remain stable. The adapters work on another computer. I don't currently have a USB meter or multimeter, so I'm trying to decide whether buying one is the best next step.