ST4R*,ECH ~
_ _ M_A_v_1_ea_4 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
optical signal, an RF video signal,
an FM IF video signal, separation
of the two audio carriers and
generation of audio, and final
generation of composite video.
Safety in disc player service
requires some understanding of
the hazards inherent to laser
radiation, and to high-voltage
potentials. A class 2 low-power
laser tube like the 1.2mW tube in
the disc players can be
hazardous to the retina of the
eye after repeated exposures.
You should avoid exposure, and
never look directly into the laser
beam. A single exposure is not
hazardous, and in fact the beam
is not strong enough to damage a
piece of lens paper. However, it
is the repeated exposure to the
laser radiation that may be
hazardous and should be
avoided.
High voltage transformers,
flybacks, and transmission lines
bring the danger of arcing to low-
resistance ground paths. You can
easily become a low-resistance
ground path by bringing your
watch in close proximity to a
flyback, for example. Be wary of
wearing jewelry or other
conductive objects when working
around high voltage sources.
Also remember that the tendency
to arc is much more pronounced
when the humidity is high. It's
interesting to note that a
requirement to be an electrical
lineman used to be right-
handedness, the idea being that
an electrical current passing
through the right side of your
body will more likely avoid your
heart, and is thus less likely to kill
you. Linemen were required to
perform their work with their left
hand in their pocket. I've not
experienced a high-voltage jolt
myself, but I've seen the effects,
and to be cautious is the wise
course to follow.
Next time, the big moment -
"Voiding Your Warranty'', or
"Opening Your Disc Player".
VIDEO FM SIGNAL
OM!WWWJMM
CD
,... ,... FM Video carrier (NTSC)
l- s
1:1:
~- o----::x::r
~ -10
b ~~---===--------s_o...;;::u-~,c:D-F_M-=-S-=--1-G~N~A=L==-------------=-.-c~
g' -15
'E 0 -20
~
Q:
t ;
VIDEO PLUS SOUND
I
C
- L.l'F-----,..:...;;
-30
_35.____ _
0
__.___._.........__~---~-~--:"=
8
6
-
FREGIUENCY SPECTRUM OF
INFORMATION ON THE VIDEO DISC
d
I
I
C:)
0
00000000000
PIT SPACING
ENCODING OF INFORMATION ONTO THE
VIDEO DISC
FIGURE 2
TANGENTIAL
TRACKING
RADIAL
TRACKING
FIGURE 3 - TANGENTIAL AND RADIAL TRACKING
10
Freq.(MHz)