NAD C 521BEE, Service Manual

- 10 -

IMPORTANT NOTES

INSTRUCTION FOR HANDLING OPTICAL SYSTEM BLOCK PICK-UP

Electrostatic breakdown of the laser diode in the optical system block may occur due to a potential difference caused
by electrostatic charge accumulated on clothing, human body, etc. A ground must be provided as follows to prevent
any electrostatic charge during unpacking or repair work.

1. Ground for Human Body
Be sure to wear a ground band (1M ohm) that is properly to remove any static electricity that may be charged on the
body.

2. Ground for Work Bench
Be sure to place a conductive sheet (1M ohm) or copper plate with proper grounding on the work bench or other sur-
face on which the pick-up is to be placed.

3. Because the static electricity charge on the clothing does not discharge through the body grounding band, do not
let clothing to get in contact with the pick-up unit. 

PRECAUTIONS FOR CHECKING BEAM EMISSION

The laser beam of this unit is focused on the reflecting surface of the objective lens in the optical system block.
Therefore, keep your eyes at least 12 inches (30 cm) away from the objective lens when the laser diode is 

ON

.

(Operation Check Method for Laser Diode and Focus Search Function.)
When the 

POWER

switch is turned 

ON

after the chucking plate is removed, observe the objective lens and confirm

that the following operations are performed properly.
(The optical system should be at the lead-in area position when it is checked at this time.)
(1) The laser should be at the innermost position after the chucking plate is removed.
(2) The diffused light of the laser beam can be seen when the 

POWER

switch is turned 

ON

.

(3) Vertical (up and down) movement of the objective lens (2 or 3 times) will take place.

INCORRECT

CORRECT

NOTE

: Laser diodes are so susceptible to damage from

static electricity that even if a static discharge does not
ruin the diode, it can shorten its life or cause it to work
improperly.

1.Grounding band

1M ohm

1M ohm

2.Conductive Sheet
or Copper Plate