BBB only power LED is glowing ?

Dear All,

when I am starting with a validated and verified bootable sdcard to BBB board, only power LED is continuously glowing. Other four LEDs are dead. I want to know how I can recover the board ? Can anyone kindly help here by supply debugging information ?

Regards.
Ankur

when I am starting with a validated and verified bootable sdcard to BBB

  How did you perform this "validated and verified bootable" check? By
using a second BBB?

board, only power LED is continuously glowing. Other four LEDs are dead. I

  If it works on one BBB but not another, the odds lean toward a dead
BBB. Have you held down the boot select button while connecting a power
supply to the BBB barrel connector? The boot select button should force it
to use the SD card for booting, totally ignoring an (potentially
corrupted/empty) eMMC (images from the last few years normally load u-Boot
from the eMMC, but that u-Boot then detects the SD card and transfers the
rest of the boot process over to it; very old images did not, and the boot
select was always needed for a cold start of SD card).

  If using the boot select succeeds, you most likely want to boot from a
FLASHER image to restore the eMMC with a usable system.