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Dave@LDF4N6 · Posted: Mon Apr 04, 2011 2:06 pm Post subject: Interpreting Oscilloscope Output

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?

fzabkar · Deadharddrive regular +3 Joined: 02 Apr 2010 Posts: 210

If your drive is a 2.5" model, then it will not draw any current from the +12V supply, ie these drives are +5V only.

In fact the oscillogram appears to show the spinup current of a motor powered from the +5V supply.

Compare it against the typical current profile for a Seagate Momentus drive in section 2.9.1.1 of the following document:

http://www.seagate.com/support/disc/manuals/ata/momentus_pm.pdf