The Transistor and its heat sink must be treated as one unit. Never attempt to remove the transistor from the heat sink.
Replacing. To replace a faulty transistor/heat sink assembley, remove the four motor housing bolts with a screwdriver. Rest the bottom plate on the blade holders, the center band is now flexible and can be lifted above the top plate. The heat sink (the semicircular plate with fins) located on the side of the motor (Fig. 1). Remove the two Phillips head screws that hold the transistor/heat sink assembley to the motor. Remove the blue wire from the transistor by removing the nut holding it in place. Pull the two wires (green and yellow) from the transistor pins in the center of the heat sink.
Before installing the new transistor/heat sink assembley examine the unit carefully. Note that the distances between the two transistor pins and the black hex head torqued bolt are slightly different (Fig. 2). The The green wire must be attached to the transistor pin closest to the black hex head bolt.
Attach the blue wire to the transistor. Do not remove the nut that holds the transistor. Use one of the nuts from the old transistor. Attach the blue wire between the new torqued nut and the old nut (Fig. 3). Do not overtighten, this can advance the torqued nut on the screw threads, causing an imbalance in the heat exchange system. CAUTION: Do not pinch the wires when remounting the unit on the motor. Also make sure that the blue wire lug does not touch the motor or the heat sink. It should only touch the transistor.