no power on Beaglebone Black Rev C

Hey All,

I purchased recently 7 beaglebone Black Revision C. I have been working with older ones for more than an year now.

But this time when I plugged USB cable from laptop and 5V DC adaptor both, then all of a sudden it stopped working.
And now none of the 3 are working. I am startled why it happened. If anyone of you people can help me out here about the problem.
Now when I insert the USB cable, the power LED glows once and then nothing happens. This is the case with all three of the bealgebones.
My guess - the power management/regulator IC is doing something because the LED glows once.
Kindly help me out here.

Were the BBB plugged into anything else at the time? Did they have anything connected to the I/O ports?

My guess is that you have a problem in the safety ground on either the laptop or in the USB power supply,
or what the BBB I/O ports was connected to. Get out your voltmeter and start measuring.

Either a plug wired wrong, or no safety ground present, in which case you can damage the BBB, if it was
also connected to ground, or something else via the I/O.

The one blink can mean that the input voltage is too high, or the input voltage is too low, or the Sitara is
drawing too much current, and is permanently damaged. It means that the power supply chip in the
BBB is alive, but has gone into self protect for some reason.

— Graham