Logitech M705 Scroll Wheel Cleaning

Remove the 5 screws from the bottom of the mouse

The bottom piece should detach from the top piece pretty easily

There's a plastic piece which can freely flop around on top of the scrollwheel. BEFORE REMOVING IT, ensure that the scrollwheel is in "free spinning" mode, not "you can feel the scroll detents" mode.

If you're not in "free spinning" mode, press it into the white button on the scrollwheel housing to switch from "detent mode" to "free spinning" mode.

Gently pry the clear plastic outward to release the pin from the black plastic piece. Repeat on the other side to remove the black plastic lever.

On the rearward side of the clear plastic scrollwheel assembly, there's a black plastic pin which holds the movable part (clear plastic) to the circuit board (black plastic).

Remove this pin by sliding it to the left

I used a screwdriver to push it from the right to get it started

Once the pin is removed, lift the scrollwheel straight up and it should easily separate from the circuit board.

NOTE: when you re-assemble the mouse, take care to lower the scrollwheel assembly straight down onto the board and not at an angle!

In particular, take extra care to ensure that the springs at the front of the mouse are still facing upward, and didn't get squished out sideways.

The "spring guard" goes around the spring and pin which are responsible for providing the haptic feedback when you scroll the wheel in "feel the detents" mode.

Remove the screw from the bottom of the scrollwheel assembly

On the left side of the scrollwheel, there's a very small pin protruding from the clear plastic which holds the black spring guard piece. Gently pry the black piece outward past this pin to remove the spring guard.

This little metal lever is what provides the haptic feedback when it engages with the scroll wheel. We need to move it out of the way so that the wheel itself can be removed

Gently pull the metal lever outward.

I do not recommend fully removing the lever. Only pull it out far enough that it is clear of the wheel.

The scroll wheel is held in place by one pin protruding from the wheel on each side, resting in a hole in each side of the clear plastic housing.

Gently pry the clear plastic piece apart by gripping with your fingers on the piece indicated by the arrow in the picture. Hold the assembly upside down so that the wheel will simply fall out.

It takes a decent amount of force to pull the plastic piece apart! Go slowly and gradually increase pressure so that you don't accidentally snap the clear plastic piece!

Now that the wheel is removed, thoroughly clean the inside of the housing, where dirt and grime can accumulate

I used a cotton Q-tip which was the perfect size for reaching into the bottom

Ensure that you clean the side walls too! The clear sides of the housing are where the infrared light passes through for the sensor to detect the scrollwheel's movement!

Since you've got it open, make sure to clear off everything in the optical path of the sensor:

The IR emitter and sensor on the circuit board

The inside and outside of the clear scrollwheel housing

The inner part of the scrollwheel itself, where you see the small slits.