VSX-LX70
73
5
6
7
8
5
6
7
8
C
D
F
A
B
E
5.2 CIRCUIT DESCRIPTION
5.2.1 PROTECTION CIRCUIT SPECIFICATION
Protection
Circuit
Process
List
DC
Detection
Circuit
Item
Purpose
Detection
Method
Process
Warning
Indication
Remarks
DC
detection
To
detect
amplifier
damage
(defect
status)
A
process
to
protect
speakers
(for
protection
of
connected
external
devices)
Detects
when
the
DC_PROTECT
port
becomes
"
L
"
.
(Pin
90
of
IC101)
Turns
muting
on
and
speaker
relay
off,
then
turns
off
the
power
after
3
seconds.
Then
flashes
MCACC
indicator.
Flashing
"
AMP
ERR
"
for
3
seconds.
Once
detected
and
turned
the
power
off,
input
a
key
never
again.
If
the
DC_DET
port
becomes
"
L
"
within
3
seconds,
the
unit
returns
to
normal
condition
automatically.
AMP
overload
To
detect
overloading
(abnormal
status)
With
low-load
driving
or
a
short
circuit
of
the
speaker
terminals
(for
protection
of
the
amplifier)
Detects
when
the
OL_DET
port
becomes
"
L
"
(checks
by
interrupt).
(Pin
17
of
IC101)
Turns
muting
on
and
speaker
relay
off,
and
immediately
turns
off
the
power.
Then
flashes
PHASE
CONTROL
indicator.
None
Overheat
detection
Self
reset
type
protection
feature
by
temperature-rise
of
heat
sink
Detects
when
the
TEMP2
port
becomes
"
H
"
.
(Pin
24
of
IC3301)
Turns
muting
on
and
speaker
relay
off,
then
turns
off
the
power
after
3
seconds.
Flashing
"
OVERHEAT
"
for
3
seconds.
If
the
TEMP2
port
becomes
"
L
"
within
3
seconds,
the
unit
returns
to
normal
condition
automatically.
12V
trigger
failure
detection
To
detect
the
shortcircuit
of
12V
trigger
output
(load
more
than
50mA)
(for
protection
of
the
amplifier)
Detects
when
the
12VDET
port
becomes
"
H
"
.
(Pin
69
of
IC101)
Turns
12V
trigger
output
to
off.
Flashing
"
12V
TRG
ERR
"
for
3
seconds.
Continue
showing
warning.
Release
the
FL
indication
by
switching
the
INPUT
SEL
or
the
turns
the
power
off.
R5714
Q5572
GAMP
GNDU
Q5571
IC5301
IC5302
R5341
OUTPUT
DC
DETECTOR
R
ch
C
ch
SR
ch
SBR
ch
SL
ch
SBL
ch
+VL
V+5UM
Normal:
High
(5V)
DC
det:
Low
(0V)
+DC
detection:
Q5571
base
is
"
H
"
.
→
Collector
of
Q5571
and
Q5572
are
"
L
"
.
-DC
detection:
Q5572
emitter
is
minus
to
the
base.
→
Collector
of
Q5571
and
Q5572
are
"
L
"
.
-VL
R5342
R5441
R5442
R5541
R5542
R5325
R5327
R5326
R5571
R5641
R5642
C5571
R182
C117
D108-2/2
D109-2/2
FFC
J43
UCOM
IC101
90
CN5302
-5
CN5301
-8
CN5702
-7
CN5703
-15
CN5602
-6
CN5601
-7
L
ch
R5041
R5042
R5141
R5142
R5241
R5242
CN5001
-7
CN102
-5
POWER
AMP
R
ASSY
R
POWER
AMP
L
ASSY
Q
POWER
PROTECT
ASSY
P
POWER
AMP
IN
ASSY
O
DIGITAL
MOTHER
ASSY
L
