B. Electrical maintenance.  1.  Changing the bulb.  a. Lay the microscope on its side, taking  extreme care especially with the eyepieces  (1) and the specimen slide holder (6). b. Unscrew the screw pointed out by the  arrow. (Fig. 5).  c.  Open the cover to give access to the bulb. d. With a cloth, carefully grasp the bulb and  gently pull, to disconnect it from its socket.  e. Do not touch the replacement bulb with  fingers. Use a clean cloth and insert the  pins of the bulb into socket. f.  If the bulb is touched accidentally, clean it ,  as finger contact may affect light transmission, and the life span of the bulb. g.  Close hinged door and tighten locking screw.  2.  Changing the fuse.  a. Using a flat screwdriver, gently press on the slot located on the fuse cap (Fig. 1) and  make a ¼ turn in the direction indicated by the arrow.  b.  Release pressure on the loosened fuse cap, and remove completely. c.  Remove the fuse located on the cap, by pulling it out, and insert new fuse. Ensure that a  0.5 Amp. fuse is used.  d.  Replace the fuse cap. e. Repeat step (a), this time making a ¼ turn in the opposite direction to that indicated by  the arrow. The cap must be closed securely. 1.  Adjusting the tension of the coarse focus control. -10-  The tension adjustment control for the coarse focus knob (Fig.5) is located between the coarse  focus knob (19) and the arm (17). The coarse focus knob tension is pre-adjusted by the  manufacturer. The ideal tension point is that which permits coarse focus knob to move as loosely  as possible, without the stage (8) moving down on its own. C. Mechanical  maintenance.  Cap of  access  Fig. 5  WARNING:  FOR YOUR SECURITY, SWITCH OFF AND REMOVE PLUG FROM POWER  SOURCE OUTLET BEFORE MAINTAINING YOUR MICROSCOPE IN ORDER TO AVOID SHOCK  OR FIRE HAZARD.