Circuit Description - Pioneer VSX-LX70 Service Manual

5

5.2 CIRCUIT DESCRIPTION

5.2.1 PROTECTION CIRCUIT SPECIFICATION
Protection Circuit Process List
Item Purpose
To detect amplifier damage
(defect status)
A process to protect speakers
DC
(for protection of connected
detection
external devices)
To detect overloading
(abnormal status)
AMP
With low-load driving or a
overload
short circuit of the speaker
terminals (for protection of the
amplifier)
Self reset type protection
Overheat
feature by temperature-rise of
detection
heat sink
12V To detect the shortcircuit of
12V trigger output (load more
trigger
failure than 50mA) (for protection of
the amplifier)
detection
DC Detection Circuit
R
POWER AMP R ASSY
+VL
IC5301
DC DETECTOR
R5341
OUTPUT
R ch
R5342
IC5302
SR ch
-VL
SBR ch
+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".
5
6
Detection Method
Detects when the DC_PROTECT
port becomes "L".
(Pin 90 of IC101)
Detects when the OL_DET port
becomes "L" (checks by interrupt).
(Pin 17 of IC101)
Detects when the TEMP2 port
becomes "H" .
(Pin 24 of IC3301)
Detects when the 12VDET port
becomes "H" .
(Pin 69 of IC101)
P
POWER
PROTECT
ASSY
CN5302 CN5702
-5 -7
Q5571
R5714
Q5572
GAMP
R5441
R5442
CN5301 CN5602
-8 -6
R5541
R5542
C ch
O
POWER
AMP IN ASSY
VSX-LX70
6
7
Process Warning Indication
Turns muting on and
speaker relay off, then
Flashing "AMP ERR" for
turns off the power after 3
3 seconds.
seconds. Then flashes
MCACC indicator.
Turns muting on and
speaker relay off, and
immediately turns off the
None
power. Then flashes
PHASE CONTROL
indicator.
Turns muting on and
speaker relay off, then
Flashing "OVERHEAT"
turns off the power after 3
for 3 seconds.
seconds.
Flashing "12V TRG
Turns 12V trigger output
ERR" for 3 seconds.
to off.
L
DIGITAL MOTHER ASSY
V+5UM
Normal: High (5V)
CN5703
CN102 DC det: Low (0V)
-15
-5
FFC J43
GNDU
CN5601 CN5001
-7 -7
L ch SL ch SBL ch
Q
POWER AMP L ASSY
7
8
Remarks
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.
If the TEMP2 port
becomes "L" within 3
seconds, the unit returns
to normal condition
automatically.
Continue showing warning.
Release the FL indication
by switching the INPUT
SEL or the turns the power
off.
UCOM
IC101
90
73
8
A
B
C
D
E
F