Circuit Description - Pioneer VSX-C302-S Service Manual

5

7.1.4 Circuit Description

1 Short-circuit-detection circuit for the amplifier
power circuit (+15 V[VP+15], VD+5, -12 V [VA-12])
Circuit for shutting the power off when VP+15, VD+5, or
VA-12 is short-circuited to ground (GND)
V+5D
Q101
R108
(Q103)
27k
R101
(R104)
to XPROTECT
µ-com C
B
Q102
C101
(Q104)
E
(C102)
1/50
• In Normal mode, as Q101 (Q103) (E2, B2, C2) and Q102 (Q104)
(E2, B2, C2) are on, the voltage at Point A is about 5 V.
The voltage at Point B is therefore about the same. As Q101
(Q103) (E, C, B) is off, Q102 (Q104) (E, C, B) is also off.
(1) When VH+(VP+15) is short-circuited to GND
As the voltage at Point B becomes almost ground potential, and
Q101 (Q103) (E, C, B) then Q102 (Q104) (E, C, B) are turned on,
the level of XPROTECT becomes low.
→ The microcomputer detects the XPROTECT level and shuts the
power to the unit off.
(2) When VH–(VA–12) is short-circuited
As the electric potential of VE at Q102 (Q104) (E2, C2, B2)
becomes the same as that at VB, Q102 (Q104) (E2, C2, B2) is
turned off. Following this, Q101 (Q103) (E2, B2, C2) is turned off,
which changes the voltage at Points A and B to a value other than
5 V. Therefore, Q101 (Q103) (E, C, B) then Q102 (Q104) (E, C, B)
are turned on, the level of XPROTECT becomes low.
→ The microcomputer detects the XPROTECT level and shuts the
power to the unit off.
(3) When VD+5 is short-circuited
The level of the XPROTECT line becomes low. The microcomputer
detects the XPROTECT level and shuts the power to the unit off.
5
6
VH+
VD+5 (VP+15)
AMP Assy
Q101
D101
E
(Q103)
E2
(D102)
B Q102
B
B2
C (Q104)
C2
R102
1k (R105)
C2
10k
A
R103
E2
D105
(R106)
(D106)
10k
UDZS7.5B
VH–
(VA–12)
6
7
2 FAN Detection Circuit
VD+5
R108
R3654
27k
1.8k
XPROTECT
D3658
µ-com
UDZS7.5B
C
C2
B2
Q3651
E
RN1901
Q3651
E2
RN1901
B2
AMP Assy
If no fan is connected between FAN+ and FAN-, or when the fan
cannot rotate because of a foreign object caught in the blades, the
BASE of Q3652 becomes OPEN, and Q3652 and Q3651 (E, C, B)
are turned off. Then Q3651 (E2, B2, C2) is turned on, and 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.
VSX-C302-S
7
8
* Refer to "3. 14 6CH AMP ASSY".
V+12F
A
Q3652
DTA124TK
B
R3658
R3657
2.2k
33(1/4W)FU
D3657
D3655
1SS355
1SS133
C3652
R3655
47/50
8.2k
Q3654
2SD2144S
R3656
(VW)
22k
V-12F
8
A
FAN+
FAN-
D3656
S5688G
B
C
D
E
F
83