Cambridge Audio 640A - Protection Circuit Diagram

Cambridge Azur 640A Integrated Amplifier
AP12707/6 Power Amp Schematic (Protection)
570mV +-1%
Q20
MJE340
To be mounted
on heatsink
R87
4k7 8th
R88
11k 8th
5
6
7
U7:B
LM393
PIC TEMP
C52
100n
R86
1k
1k / (1k + 11k) with 570mV transistor
voltage gives 92deg C cutout
R92
1k 8th
For 1mA
R93
10k 8th
R89
100R 8th
R90
10R 8th
digital
3
2
1
8
4
U7:A
LM393
D12
1N4148
+5V
Speaker short circuit tester
R91
4k7 8th
OpenC
Senses a DC resistance of 2 ohms or less
3
2
7
4
6
1 8
5
U1
NE5534
R104
220k 8th
R105
220k 8th
R13
1M 8th
R12
1M 8th
C6
5p
C5
5p
C4
100n
C3
100n
-15V
RICLIP
RFCLIP
R63
220k 8th
R62
220k 8th
R60
1M 8th
R61
1M 8th
C35
5p
C34
5p
LICLIP
LFCLIP
Q6
BC337
Q1
BC327
digital
ROCLIP
LOCLIP
D25
1N4148
D26
1N4148
LOCLIP
ROCLIP
digital
PIC CLIP
D30
10V Zener 400mW
R6
4k7
D29
10V Zener 400mW
Q4
BC337
digital
R7
4k7 8th
Q3
BC337
D21
1N4148
D22
1N4148
ROCLIP
LOCLIP
Q2
BC327
R9
10k 8th
R10
10k 8th
PIC DC
RE1
RE2
R24
2k2
R23
2k2
R25
470R 8th
R45
47k
R47
18k
D7
4V7 Zener 400mW
g1
PIC OVERCURRENT/SHORT
+45V
R46
4k7 8th
R48
18k
C27
4.7n
D6
1N4148
Q5
BC337
R5
4k7
R4
4k7 8th
R2
10k 8th
R3
10k 8th
digital
+5V-1
C1
1u 16V
PIC OVERCURRENT/SHORT
PIC DC
PIC CLIP
PIC TEMP
PIC SPEAKER
digital
+5V-1
PIC SPEAKER
+15V
C15
220p
D23
1N4148
D24
1N4148
ROCLIP
LOCLIP
D27
1N4148
D28
1N4148
ROCLIP
LOCLIP
R49
47k
3
2
7
4
6
1 8
5
U6
NE5534
C36
100n
C37
100n
+15V
-15V
digital
digital
LK13
LINK
LK11
LINK
LK12
LINK
g1
LK10
LINK
PIC STANDBY
1
2
3
4
CN5
H4 2.54mm
1
2
3
CN8
H3 2.54mm
PIC STANDBY
+15V
digital
LK20
LINK
LK17
LINK
+5V-1
+5V-1
+5V-1
+5V
LK16
LINK
R94
4k7 OpenC
R95
100R
R11
100R
R1
10k 8th
R8
10k 8th
LK4
LINK
LK3
LINK
LK14
LINK
LK15
LINK
LK19
LINK
LK2
LINK
1
2
3
4
5
6
7
8
CN7
H8 2.54mm
+5V
LK26
LINK
R106
100k
R107
100k
R108
470R 8th
C69
220p
C70
220u 16V
C71
220u 16V
+45V2
-45V2
R109
820R 8th
R110
820R 8th
LE1
LE2
R111
2k2
R112
2k2
R113
470R 8th
C72
220p
R114
100k
R115
100k
R66
470R 8th
C73
220p
C74
220u 16V
C75
220u 16V
+45V3
-45V3
R117
820R 8th
R118
820R 8th
LORO
Q19
MPSA42/43
Q35
MPSA42/43
Q22
MPSA42/43
Q36
MPSA42/43
Q21
MPSA92/93
D31
1N4002
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