To replace the speed sensor in this trainer, please do as follows:
Remove the resistance unit from the frame
The electronic board is located on the opposite side of the flywheel, so:
Remove the screws that hold the cover in place on the opposite side (the full one) on the bottom of the resistance unit, please see the following pictures
Use a flat-bladed screwdriver to gently push outwards in the two points indicated as follows, in such a way as to remove the cover
Once the cover has been removed you'll have access to the electronic board:
Unplug the speed sensor from the board (the 3 cables connector in the pic below).
Remove the ferrite core as shown in the pic below.
Remove the screw and the washer as shown in the pic below.
Remove the sensor completely.
Apply the new sensor on the housing as shown in the pictures below. Pay attention to insert it on the proper side (the housing has the same shape of the sensor).
Place again the screw and the washer.
Apply the ferrite core and then plug the sensor on the board.