I have an old broken Canon PowerShot SD1100 IS compact point-and-shoot digital camera, and I'm trying to see if I can find where it broke. My first candidate didn't pan out so I went looking around inside the lens assembly to find my second candidate: an actuator moving a lens element.

From right to left in this picture, the members of this cast: a stepper motor only a few millimeters in diameter turns electricity into mechanical motion. A lead screw translating rotational motion into linear motion moving the element up-down. A round metal bar acting as the linear rail for this actuator guiding its path. And finally, a spring that compensates for backlash by pulling the lens nut against one side of the lead screw thread.

Near the left edge of this picture, blurry out of focus at around 8 o'clock, is a bit of yellow FPC (flexible printed circuit) attached to a small optical interrupter sensor. A small plastic tab on the lens element blocks the beam, so the sensor can act as a homing switch for this lens actuator. It would also explain how the camera's brains knew something was wrong here.

The other side of this mechanism is underneath that shiny metal plate in the top right corner, held by a single screw that is threaded into a metal plate at the base of the tiny stepper motor. (I realized that fact when I loosened the screw and the motor fell out.)

Wow, that is a super thin gearbox. Each of these gears are less than 1mm thick, maybe 0.5 mm?

And here I see clear indication of mechanical failure. The little red gear is press-fit into this end of the lead screw. In this picture, the crack allowed us to see through it to the white gear beyond. The whole gear and shaft it is sticking out above the gearbox in this picture because, with the thin metal plate removed, the backlash compensation spring was free to contract.

I want to get a closer look at the crack, but this is about the limit of my camera with macro lens. Time to try my new digital microscope.

The inexpensive digital microscope sensor is a lot noisier, as if I had turned my Canon sensor up to 12800 ISO. But it had the right lens for more magnification and give me the closer look I sought. Yep, that gear is definitely broken. What might it mean, and what might I do about it?