Pioneer S-DV900SW Service Manual page 39

5
3 FAN detection circuit
C
6CH AMP
VD+5
R3654
R108
1.8k
27k
to
XPROTECT
D3658
(µ-com)
UDZS7.5B
C2
C
B2
Q3651_2/2
B
RN1901
E2
E
Q3651_1/2
RN1901
If no fan is connected between FAN+ and FAN-, or when the fan
cannot rotate because of a foreign object caught in the blades,
current will not flow to R3657, and Q3652 and Q3651-
B) are turned off. Then Q3651-
the level of XPROTECT becomes low.
→ The microcomputer detects the XPROTECT level and shuts
the power to the unit off.
When FAN+ and FAN- are short-circuited, the electric potential at
Point A becomes higher than GND level by the addition of the
values at D3656 and D3657. As this value is lower than that at
D3658, Q3651 (E, C, B) is turned off, Q3651 (E2, B2, C2) is
turned on, and the level of XPROTECT becomes low.
4 DC detection circuit of SP terminal
D
R3357
(R3457)
18k
Front L ch
(SW, SL)
Q3605
Front R ch
(C, SR)
R3358
+
R3603 C3602
(R3458)
10k 100/10
18k
• 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
VPF+15
A
Q3652
DTA124TK
R3658 R3657
+
33(1/4W)
2.2k
FAN+
C3652 D3657
1SS355
47/50
D3655
1SS133
Q3654
FAN–
2SD2144S
R3655
8.2k D3651-D3654
1SS133×4
R3656
22k
V-12F
(E, C,
1/2
(E2, B2, C2) is turned on, and
2/2
6CH AMP
C
POWER Assy
VD+5
+5V
R108
Q3606 27k
E
B
XPROTECT
C
Q3607
Q3604
6
7
5 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.
S-DV900SW
7
8
6CH AMP
C
TH111
NCP18WF104J03RB
to
XPROTECT
R113
220
Q111
2SC4081
R112
1k
8
A
B
C
D
E
F
39