I used an Atola to run diagnostics on a hard drive. The following
link shows the oscilloscope output of the PCB during the power on
cycle of the drive.

http://ldf4n6.serveftp.net/images/HDD-Oscilloscope.jpg

The 12V reading is a flat line. I assume this means the PCB is having
power problems; however, I do hear the drive making abnormal grinding
like sounds.

Can someone elaborate on the interpretation of the oscilloscope output
and what it means?

From the current graph I can tell that this is probably a notebook drive, which means it does not need 12V. Furthermore, I can clearly see HDD spin up pattern on the 5V graph, and some attempts to initialize as well.

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Dmitry