Technics SL-P202A - Page 41

72020
3-1-7 Start-up procedure
STAGE 3
The whole start-up procedure is A
sequenced by the voltage aopoas A smooth transition is made from the
capacitor C2513. Capacitor C2513 is amplified sum current (I1 + I2 + 13 +
charged by an internal current source 14) foc whe: MoEmal teed FOCUS. iror
of 1 pA non. signal
Together with a starting capacitor of
270 nF, a starting-up time of
approximately 0.3 sec. is reached.
It - 12 “a T4 - 13
I1 + I2 T4 + 13
The spot is now almost focused on the
The start-up procedure is divided in :
reflective layer of the disc.
stages. The’ procedure is started by
putting a logical low level at the
Si/RD
input.
The
signals
to
the
FE
pin.
STAGE
1
(starting-up
current
+
11
+
I2
VsC
START
UP
DIAGRAM
+
13
+
T4)
‘
STAGE
2
(starting-up
current
+
11
+
I2
+
13
+
T4)
4
I1 -
12
I4
-
13
3
phage
3:°
744
12
*
Iba
13
This
should
be
almost
0
1
The
signal
to
the
FE
lag
pin.
V(Vj)
BIAGE?
STAGE
2
STAGE
3
STAGE
4
|
—
I@
|
sc
eye
Stage
4]
(11
+
I4)
-
(13
+
12)
+
the
®
+100HA
+
i1
+12
+13
+14
normalized
FE
(like
in
stage
t
|
®
—100uA
+i1
+
i2
+i3
+
i4
3)
Eiivene
©
focus
unit
is
in
focus
at
output
The
arm
is
kept
at
the
inside
recess
by
FE
0
means
of
a
binary
word from
_
the
©
time
microprocessor
at
BO,
Bi, B2,
and
B3
of
the
radial
error
processor.
Laser
turns
on
and
the
objective
is
moved
to
the
center
of
the
disc.
The
turntable
motor
is
switched
on.
The
FE
pin
delivers
a
positive
going
starting
current
of
100
vA
+
the
sum
current
(11
+
12
+
13
+
T4).
Note
the
I.f.
a.g.c.
does
not’
see
light,
so
max
amplification.
The starting current is_ reversed,
gradually causing the -objective to go
down. This process is stopped when the
starting current equals the amplified
sum current (11 + I2 + I3 + T4).
Note: I1 + I2 + 13 + I4 = 100pA
UBD,