I have a 4TB Hitachi drive from a Touro external unit. It was working for about a month, then I brought it in a plane (carry-on), plugged it in after the flight, and it doesn't spin up. When it is plugged in to power you can hear a faint click if you hold your ear to it followed by an audible almost electronic-sounding buzz for almost a second. These alternate six times, then there are a few more clicks and the drive is silent. One of the solder points on the power jack looked like it might have been a little burned, so I bought a new enclosure hoping for an easy fix, but no such luck - same exact symptoms.

What's my likely diagnosis and what would it take to try to get the data off?

The drive was kicked hard (most probably involuntarily) but now there is an internal mechanical problem (have 2-3 ideas but only a visual inspection in clean room can tell). NEVER fly HDDs that way again.

P.S. if you don't have valuable data, get another drive and carry on, otherwise you need first to have the drive opened in clean room and then evaluated. If one of my ideas is right it should not be so expensive, AT THIS STAGE