Pioneer XV-DV940 Service Manual page 105

5
4 When DC is generated at the output because of
a failure in the AMP system, etc.
[Sub Woofer side]
D
R3357
(R3625)
(R3457)
18k
Front L ch
(SW, SL)
Q3605
Front R ch
(C, SR)
R3358
+
C3632
R3603
(R3626)
10k 100/10
(R3458)
10k
• In Normal mode, both Q3605 and Q3604 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 Q3605 becomes higher than that at the operation point,
Q3606 (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
Q3604 is turned on, and XPROTECT is activated.
5
6
[Sub Woofer side]
6CH AMP
C
POWER Assy
Assy
VD+5
+5V
R108
Q3606
27k
E
B
XPROTECT
C
Q3604 Q3607
6
7
5 When abnormally high temperature is detected
by the thermistor
5 -1 IC81 abnormal temperature detection circuit
VD+5
IC81
NJM7805FA
A
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.
XV-DV830
7
8
[Sub Woofer side]
6CH AMP
C
Assy
TH111
NCP18WF104J03RB
to
XPROTECT
R113
220
Q111
2SC4081
R112
1k
8
A
B
C
D
E
F
103