Technics SU-3 - Page 8

VR3OI-|
(Volume)
VR302
(Balance)
VR30I- 2
(Volume)
_SU-3
SU-3
|
i
Tone control Oon
C)
treble | 0 off
2
bass
IC30l
SVIK4121— 2ML
2CH. power amplifier
arate tet at
S2 (Super bass)
|
| | ~P
Speaker
terminal
(L ch.)
detection
circuit
OO xa MG?
H
Headphones jack
Current
stabilizer
OOO OOOO
SOO IOOO! O
detection
circuit 3
Speaker
terminal
(Rch.)
5
ecorerenenon yep revececocerees.
evosesene:
ROHR RCRO IR 0. CORIO! aan RIMM MMMM MMR! ann MMI?
Tone control
treble
bass
IC40I
AN7072
Muting & Speaker protection
Posistor (130 C)
AC Line
Pye (50/60Hz)
| ne te cal
Power
ON/OFF
det.
SOOO a TORII REN 6, IRI IIR I ICICI IID
Hi CIRCUITS TO BE CHANGED AND THE AREAS |
e
Power
source
circuit
|
[EF]
area
[EF]
is
available
in
France.
[XL]
area
[XL]
is
available
in
Australia.
= —_-—_—_—_- SS
SUP 26530F
AFI T500mA
“SUP 26530F
AF i T500mA
e e
[NAC 50Hz
220Vv
sees a ey oer
[XA] is available in Southeast Asia, Oceania, Africa,
[EW]
area
[EW]
is
available
in
Switzerland.
[XA]
area
|
Middle
Near
East
and
Central
South
America.
A
Ac 50/60Hz
NO/120/ 220,
7240V
®
Operational
description
of
IC
(I1C401)
for
muting
(with
power
on/off,
overload)
|
1. Muting operation with power ON.
With
power
turned
ON,
AC
voltage
is
applied
to
terminal
@)
of
1C401.
Then,
condenser
C408
connected
to
terminal
@
is
charged,
and
the
voltage
of
terminal
()
gradually
rises.
When
the
voltage
reaches
about
—AV
(about
5
sec.
after
power
ON),
the
muting
circuit
turns
off,
and
then
—30.6V
is
generated
at
terminal
@).
The
voltage
of
terminal
@
is
supplied
to
the
voltage
amplifier
circuit
of
|C301,
thus
operating
power
IC;
2. Muting operation with power OFF.
With
power
turned
OFF,
condenser
C408
connected
to
terminal
(1)
is
discharged,
causing
the
voltage
of
C408
to
drop,
and
then
the
muting
circuit
in
IC
turns
ON.
With
the
muting
circuit
turned
ON,
the
voltage
of
terminal
@)
becomes
OV,
and
then
power
supply
to
the
voltage
amplifier
circuit
of
1C301
is
discontinued.
3.
Muting
operation
with
power
amplifier
over-loaded.
|
|
With
speaker
terminals
short-circuited,
a
large
quantity
of
current
flows
into
R315
(R316),
causing
the
voltage
rise.
The
voltage
causes
0401
(0402)
to
turn
ON,
and
then
overload
detecting
signal
is
applied
to
terminal
G)
.
When
the
potential
difference
between
terminals
@)
and
©
reaches
about
0.7V,
condenser
C408
is
discharged
the
same
as
for
muting
operation
with
power
OFF.
Asa
result,
the
muting
circuit
turns
ON and the voltage of terminal () becomes OV.