Sony PS-X75 - Page 7

1-4, CIRCUIT DESCRIPTION
1-4-1. When the POWER Switch is turned on (see Fig. 1):
The waveform shaper, consisting of IC111, turns
the voltage at terminal (3) of IC102 to low level
“0” in half a second during which C112 is charged
with B+ power. Asa result, IC102 is reset.
OV
Fig. 1 S501 (POWER}: ON
1-4-2. Arm Lifter Raising/Lowering Circuit(see Fig. 2):
Turning the power switch on raises the arm lifter.
[Lowering the arm lifter]
When S508 (UP/DOWN) is depressed, the voltage
at
terminal
(24)
of
IC102
becomes
high
“1”.
This
turns the voltage at terminal (6) of IC112 to positive
and
the
voltage
at
terminal
(7)
to
negative.
Asa
result, Q131 switches on.
The
potential
of
the
terminal
(2)
of
IC112
now
becomes
negative
and
the
output
of
the
terminal
(1)
goes
positive.
This
turns
Q128
on.
| aa
OV
ARM LIFTER
DOWN
Fig. 2
-—-7-—
| PS-X75
This means that the microprocessor (IC102)
does not operate for 0.5 seconds after the power
switch is turned on.
Also, buttons can be effectively pressed after
it is assured that the tonearm has been on the arm
rest for about 0.5 seconds.
S501 (POWER): ON
rn IT
Since both Q128 and Q131 are on, current passes
through L505 (lifter drive coil) in direction A, thus
lowéring the arm lifter.
[Raising the arm lifter]
When S508 is depressed, the voltage at terminal
(25) of 1C102 becomes high “1”. This turns the
voltage at terminal (7) of IC112 to positive, switching
Q130 on.
Since Q130 is on, a negative voltage appears at
terminal (1), turning Q127 on. Now that both Q127
and Q130 are on, current passes through L505 in
direction B, thus raising the arm lifter.
ARM LIFTER ARMLIFTER
DOWN
ARM LIFTER ARMLIFTER
DOWN uP