Electronic – test a USB port with a multimeter?


After a recent thunderstorm (Derecho), we had a power outage. After power restored, I noticed my desktop's USB ports (and a PS/2 port) were not responding, even at a BIOS level. Tried a known good keyboard, not plugged in at the time. Still nothing. I'm thinking the USB ports are shot, but I want to test them.

I have a USB cable and a multimeter. I've stripped the cable and found hot and ground (orange and black). My only question is, how do I connect it to the multimeter? I have one of these cheaper ones, not sure how good it is. I've never used one before, and the manual doesn't make sense to me.

Here's the link to more details of my multimeter.

Best Answer

If you just want to check that +5V is being supplied, you would connect the hot wire to the red lead of your multimeter plugged into the V(Ω)mA position and the ground wire to the black lead of your multimeter plugged into the COM position. Set the Multimeter to DCV 20 mode and it should show around 5V.

If that works, then another test you can do is get a 1.5kohm resistor and connect it between either of the data wires and the hot wire while your computer is on. Your computer should say something like "USB device not recognized" or something to that effect.

Obviously, be careful not to short any of the wires together while you're doing this.

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