Pioneer XV-DV434 Service Manual page 99

5
QQ
3 7 63 1515 0
4 When DC is generated at the output because of
a failure in the AMP system, etc.
R3605
(R3625)
(R3615)
27k
Front L ch
(SW, SL)
Front R ch
(C, SR)
R3606
R3638
(R3626)
(R3616)
27k
• In Normal mode, both Q3637 and Q3638 are off.
(1) When positive (+) DC voltage is generated at the SP
terminal
When positive (+) DC voltage is generated at the L or R channel,
and VB of Q3637 becomes higher than that at the operation point,
Q3632 (E, C, B) is turned on, and the level of XPROTECT
becomes low.
→ The microcomputer detects the XPROTECT level and shuts
the power to the unit off.
(2) When negative (-) DC voltage was generated at the SP
terminal
Q3638 is turned on, and XPROTECT is activated.
TE
L 13942296513
5 When abnormally high temperature is detected
by the thermistor
5 -1 IC81 abnormal temperature detection circuit
IC81
NJM7805FA
R111
1k
The voltage at Point A becomes the divided voltage of TH111
and R111//R112 (combined resistance of parallel-connected
resistors R111 and R112.) In Normal mode, the resistance at
TH111 is much higher than R111//R112, and Q111 is off. (Note
that the resistance at TH111 becomes lower as the temperature
increases.) If the solder temperature at IC81 increases abnormally,
the temperature at TH111 (thermistor) mounted closest to the land
of IC81 increases accordingly, and the resistance at TH111
decreases.
When the temperature at TH111 reaches 90-110_C (varying
according to conditions,) the voltage at Point (A) becomes high
www
enough to turn Q111 on, and the level of the XPROTECT line
becomes low. The microcomputer detects the XPROTECT level
and shuts the power to the unit off.
.
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POWER Assy
VD+5
+5V
Q3632
E
B
C
Q3637
+
C3632
Q3633
Q3638
10k 470/6.3
VD+5
6CH AMP
D
Assy
TH111
NCP18WF104J03RB
to
XPROTECT
A
R113
220
Q111
2SC4081
R112
1k
x ao
y
i
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6
8
6CH AMP
D
Assy
VD+5
R9506
R108
27k
27k
XPROTECT
Q Q
3 6 7 1 3
u163
.
XV-DV333
6
7
2 9 9 4 2 8
POWER Assy
XSR3008
RS3
Q3646
PAN217
DTA124EUA
1 5 0 5 8 2 9 9 4
m
co
7
8
9 9
A
RY1
Q51
2SD1858X(QR)
R53
18
R54
18
B
C
2 8 9 9
D
E
F
99
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