45
VSX-LX52
5
6
7
8
5
6
7
8
A
B
C
D
E
F
5.2 CIRCUIT DESCRIPTION
GAMP
R5747
C5743
C
N
1250
-3
C
N
1401
-27
[1] 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 XDCERR port
becomes "L".
(Pin
8
0 of IC3001)
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, the power
cannot be turned on again
(*). If the XDCERR port
becomes "L" within 3
seconds, the unit returns
to normal condition
automatically.
AMP
overload
To detect overloading
(abnormal status)
W
ith low-load driving or a
short circuit of the speaker
terminals (for protection of the
amplifier)
Detects when the XOLERR port
becomes "L" (checks by interrupt).
(Pin 71 of IC3001)
Turns muting on and
speaker relay off, and
immediately turns off the
power. Then flashes
PHASE CO
N
TROL
indicator.
N
one
(*) To restore the previous staus, follow the procedure
described in “How to Enter Release Mode” (P.49)
then turn the unit back on.
R5744
R5746
R5742
Q5742
GAMP
G
N
DU
Q5741
Q5744
Q5743
Q5301
Q5302
R5341
OUTPUT
DC DETECTOR
R ch
C ch
SR ch
SBR ch
SL ch
SBL ch
+
V
L
V
+5UST
V
+5_ST
N
ormal: High (5
V
)
DC det: Low (0
V
)
+DC detection: Q5741/Q5743 base is "H".
–> Collector of Q5741, Q5742, Q5743 and Q5744 are "L".
-DC detection: Q5742/Q5744 emitter is minus to the base.
–> Collector of Q5741, Q5742, Q5743 and Q5744 are "L".
-
V
L
R5342
R5441
R5442
R5541
R5542
R5325
R5327
R5326
R5741
R5641
R5642
C5741
R3057
C3015
D3005
D3004
UCOM
IC3001
8
0
C
N
5
8
05
-4
C
N8
014
-4
C
N8
005
-16
L ch
R5041
R5042
R5141
R5142
R5241
R5242
C
N
3001
-13
POWER AMP ASSY
DISPLAY ASSY
J
H
COMPONENT
ASSY
D
DIGITAL MAIN
ASSY
E