 Step 1. The focus drive has a flexible coupling that mounts onto the fine focus shaft and a sleeve with a split ring that tightens around the coarse focus knob. |
 Step 2. Unscrew the set screw that fixes the fine focus knob with a 1.5 mm wrench. |
 Step 3. Remove the fine focus knob. |
 Step 4. Disassemble the focus drive as shown and push the flexible coupling onto the focus shaft. While doing it press on the focus knob on the other side of the microscope to prevent the shaft from sliding out. |
 Step 5. Tighten the flexible coupling around the focus shaft with a socket screw and push the focus drive tube over the coarse focus knob. |
 Step 6. Insert the back lid into the focus drive and tighten all set screws: the lid screw, the screw that fixes the motor inside the drive, and three screws that tighten the split ring around the coarse focus knob. |