The old version has the 5mm decoder soldered on a small PCB which is connected to the main board by a 3-wire ribbon. You have to de-solder the wire connected to the small PCB side to complete the remaining work.

On the new version, the 5mm decoder is directly connected to the roller. It is recommended to use a small plastic spudger to unlatch the right side of roller shaft first, then carefully take out the encoder and roller together. Use a spudger if needed. There is a tinny shaft connects to the encoder tends to break.

After replacing the encoder, either solder it back to the small PCB for the old version, or three wires to the three pins of encoder. It doesn't matter if Red is on the left or right. However, make sure the encoder hexagon hole is facing the roller.

For the old version, make sure the encoder is soldered in the same way when you took the old one out. The worst case is the volume control function will be reversed.

For the new version, the 3-pin JST ZH 1.5mm connector has three wire colors, Red, Black, and Blue. The Blue wire is for the GND, and make sure it's connected to the encoder middle pin. Solder the other two wires to the remaining two pins.

Insert the roller tiny hexagon shaft to the encoder. For the OEM parts, the plastics side of encoder is facing the roller.