Here the top cover has been removed and part of the drive controller can be seen. Two circuit boards mounted one on top of the other make up the complete controller. The top board, visible here, is almost entirely made with discrete logic ICs.  This was common in the past but is never seen today.

The top board is hinged so that it can be moved without disconnecting. 'Click' the image to see the second board underneath.  Disk drive controllers are basically computers which are dedicated to controlling and monitoring the drive. 

Want to dismantle it more? Just 'Click' on the spanner icon below.