Pioneer XV-EV61 Service Manual page 132

1
4 When DC is generated at the output because of
a failure in the AMP system, etc.
A
R3605
(R3625)
(R3615)
27k
Front L ch
(SW, SL)
Front R ch
(C, SR)
R3606
+
R3638
(R3626)
10k
(R3616)
27k
B
• 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
C
terminal
Q3638 is turned on, and XPROTECT is activated.
D
E
F
132
1
2
EVOL
K
N
SP-TERMINAL
Assy
Assy VD+5
+5V
R108
Q3632 27k
E
B
XPROTECT
C
Q3637
C3632
Q3633
Q3638
470/6.3
2
3
5 When abnormally high temperature is detected
by the thermistor
5 -1 IC81 abnormal temperature detection circuit
IC81
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
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.
5 -2 D22 abnormal temperature detection circuit
If the solder temperature at D22 becomes abnormally high
because of short-circuiting between AC - and +, or AC - and -, this
protection circuit is activated.
D22
R131
560
1%
The voltage at Point A becomes the divided voltage of TH131
and R131//R132 (combined resistance of parallel-connected
resistors R131 and R132.) In Normal mode, the resistance at
TH131 is much higher than R131//R132, and Q131 is off. (Note
that the resistance at TH131 becomes lower as the temperature
increases.) If the solder temperature at D22 increases abnormally,
the temperature at TH131 (thermistor) mounted closest to the land
of D22 increases accordingly, and the resistance at TH131
decreases.
When the temperature at TH131 reaches 107-125_C (varying
according to conditions,) the voltage at Point (A) becomes high
enough to turn Q131 on, and the level of the XPROTECT line
becomes low. The microcomputer detects the XPROTECT level
and shuts the power to the unit off.
XV-EV61
3
4
VD+5
TH111
NCP18WF104J03RB
to
XPROTECT
A R113
220
Q111
2SC4081
R112
1k
VFL+5
TH131
NCP18WF104J03RB
to
XPROTECT
A R133
220
Q131
2SC4081
R132
680
1%
4