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.

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    \$\begingroup\$ Unless you have an oscilloscope it would be difficult to capture any data signals on D+ and D-. If you are only using a multimeter then I'd say all you could test are the power and ground; you should expect to see +5V across these two leads. \$\endgroup\$
    – sherrellbc
    Commented Jul 2, 2014 at 20:56
  • \$\begingroup\$ @sherrellbc I see your difficult and raise it to imposible. \$\endgroup\$
    – Matt Young
    Commented Jul 2, 2014 at 20:59
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    \$\begingroup\$ No, I am not trying to capture signals on the data lines. Just power and ground. \$\endgroup\$ Commented Jul 2, 2014 at 22:00
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    \$\begingroup\$ Just checking power and ground most likely will not tell you anything useful. The USB bridge chips generally do not supply power to the ports; the power comes from somewhere else on the board. It is possible that the ports are receiving power yet the interface chip is damaged. \$\endgroup\$ Commented Jul 2, 2014 at 22:20
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    \$\begingroup\$ Well, it's a start I guess. I like to start from the bottom up, checking things like power and then get more complicated. Turns out everything is fine. USB ports suddenly started responding like normal. Hopefully it won't revert. \$\endgroup\$ Commented Jul 3, 2014 at 3:55

1 Answer 1


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.

  • \$\begingroup\$ Alright, I'll give it a try in a few hours. Thanks! \$\endgroup\$ Commented Jul 2, 2014 at 22:00

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