I have an old Canon PowerShot SD1100 IS compact point-and-shoot digital camera, and I think there's a mechanical failure keeping it from starting up. All the mechanical bits are in the lens assembly at the core of the camera. As soon as I dug it out of the chassis, my attention was immediately drawn to a motor at the bottom.

I removed four screws that provided most of the holding power for keeping this assembly together, but as I felt around trying to pry it open, I discovered there were a few plastic clips as well. Sadly I realized this after I had already destroyed those clips. Those two clips became the first and second irreversibly destructive thing I did during this teardown. Darn.

But at least I got it open! In this picture, the front (left) and back (right) halves of the assembly are still connected in the middle by several yellow FPC (flexible printed circuit) cables. Since I was here to look for a mechanical failure, my eyes went immediately to the motor and the worm gear attached to its output shaft. I saw irregular surfaces in a lighter shade of gray and thought it indicated failure with black plastic turning gray due to stress. I took a closer look and saw my first impression was wrong. The irregular gray surface was just lubricant, and the worm gear was fine.

At the end of the worm gear is a three-bladed structure that I first thought was a cooling fan, but there was no tilt to the "fan blade" and no air path to the motor. A closer inspection of enclosure front found sensor that would wrap around these "fan blades". They look like optical interrupter sensors, so it's not a fan but an encoder disc.

I then visually inspected every gear under my new digital microscope, and found no visible damage to any of the gears. Hmm. I guess the problem isn't here, and I need to look around for another candidate.