McIntosh C8AC Service Manual

11 12
MAIN 751376 SCH 2 of 3
2
+5V
TURN ON
CONTROL
4
2
1
3
Vcc
GND
5
U29
+5V
PGND
4
2
1
3
Vcc
GND
5
U27
+5V
4.75K
R51
47.5K
R56
22.1K
R57
+5V
D20
4
2
1
3
Vcc
GND
5
U4
4
2
1
3
Vcc
GND
5
U3
L SM
R SM
+5V
10K
R25
4
2
1
3
Vcc
GND
5
U11
+5V
4
2
1
3
Vcc
GND
5
U26
+5V
2.21M
R36
.1µF
C23
+12.6V +12.6V
3
1
2
Q4
DRIVER
PC OUTPUT
12V
0V
4
2
1
3
Vcc
GND
5
U6
+5V
D19
47.5K
R30
4.75K
R23
.1µF
C22
2.21K
R29
47.5
R32
3
1
2
Q6
3
1
2
Q5
PC OUTPUT
DELAY
10K
R28
10K
R27
12
14
15 11
13
16
9
7
6
4
2
1
10
3
5
8
CLK
CE
RST
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
CoutVss
Vdd
U16
+5V
AC DETECTOR
0V
4
2
1
3
Vcc
GND
5
U12
+5V
3
1
2
Q7
10K
R39
100K
R41
.1µF
C30
+5V
.1µF
C29
12
14
15
11
16
97
6
4
2
1
10
3
5
8
S0
ENA
Q0
Q3
Q1
Q2
Vss
Vdd
R0
S1
R1
S2
R2
S3
R3
U25
L RED
ORN 1
R RED
GRN
ORN 2
ORN 3
ORN 4
ORN 5
ORN 6
ORN 7
12
14
15
11
16
97
6
4
2
1
10
3
5
8
S0
ENA
Q0
Q3
Q1
Q2
Vss
Vdd
R0
S1
R1
S2
R2
S3
R3
U24
+5V
.1µF
C37
+5V
+5V
4
2
1
3
Vcc
GND
5
U20
+5V
4
2
1
3 5
Vcc
GND
U28
+5V
+5V
MUTE
.01µF
C26
.1µF
C28
.47µF
C25
2.21M
R38
2.21M
R35
+5V +5V
7
6
4
2
1
3
5
8
TRIG
OUT
DISCH
THRESH
CONT
Vcc GND
RST
U10
RUN
4
2
1
3
Vcc
GND
5
U14
+5V
+5V
.1µF
C40
.1µF
C24
WARM-UP DELAY
AND
2.21M
R45
.47µF
C34
4
2
1
3
Vcc
GND
5
U17
+5V
5V
0V
5V
5V
5V
-11V
5V
+5V
.1µF
C31
+5V
.1µF
C39
+5V
.1µF
C33
+5V
+5V
10K
R24
PS SM
+5V
AC ON
47.5
R59
BAL
UNBAL
STEREO
MONO
INPUT
MODE
J26:2
J26:1
J27:2
J27:1
MODE SW
INP SW
POWER CONTROL
J29:15
J29:16
J29:17
J29:18
J29:11
J29:10
J30:3
J30:9
J30:8
J30:11
J30:12
J30:6
J30:5
J30:1
TUBE LT
AMPLIFIERTUBE LIGHT
J31:6
J31:10
J29:12
J29:13
47.5
R58
47.5
R33
J29:14
J31:9
J31:1
J31:7
J31:4
J29:8J29:7
J29:1
J29:4
J29:2
J31:3
J31:12
2.21K
R40
TUBE
LIGHT CONTROL
8
9
10
11
12
13
141
2
3
4
5
6
7
Q/Q SEL
Q
MODE
NC
A
B
Vdd
Vss
MR
AR
NC
Rs
Ctc
Rtc
_
U18
.22µF
C32
221K
R43
100K
R42
22.1K
R44
+5V
+5V
J29:5 J29:6
PC IN
PWR SW
ENABLED
DISABLED
AUTO OFF
J28:2
J28:1
+5V
4.75K
R34
4
2
1
3
Vcc
GND
5
U7
+5V
PWR RLY
PC ON
PC ON
12
14
15
11
16
97
6
4
2
1
10
3
5
8
S0
ENA
Q0
Q3
Q1
Q2
Vss
Vdd
R0
S1
R1
S2
R2
S3
R3
U8
4
2
1
3
Vcc
GND
5
U5
+5V
10K
R26
+5V
+5V
4
2
1
3
Vcc
GND
5
U15
+5V
4
2
1
3
Vcc
GND
5
U19
+5V
4
2
1
3
Vcc
GND
5
U21
+5V
4
2
1
3
Vcc
GND
5
U22
+5V
4
2
1
3
Vcc
GND
5
U23
+5V
4
2
1
3
Vcc
GND
5
U13
+5V
4
2
1
3
Vcc
GND
5
U9
+5V
AUDIO
+5V
220µF
C35
+5V
22.1K
R49
4
2
1
3
Vcc
GND
5
U30
+5V
TUBE LT
PC OUT
PC OUT
SENTRY
+5V
.1µF
C41
5V
AUTO OFF TIM ER
+5V
.1µF
C42
+5V
22.1K
R48
5V
5V
0V
0V
0V
0V
0V
0V
0V
.47µF
C19
.47µF
C20
.47µF
C21
0V
0V
0V
31
2
10k
10k
Q8
31
2
10k
10k
Q10
31
2
10k
10k
Q11
31
2
10k
10k
Q12
31
2
10k
10k
Q13
31
2
10k
10k
Q14
31
2
10k
10k
Q15
221K
R37
47.5K
R52
FIL C
10µF
C27
2.21K
R31
1 2
3
G
D
S
Q9
332K
R55
68.1K
R50
2.21M
R54
2.21M
R53
-225V
2.21M
R47
.1µF
C38
POWER UP
DELAY
0V
100K
R46
+5V
10µF
C36
5V
0V
MONITOR
TRIGGERS
SENTRY
AND
LATCHES
INP SW
MODE SW
AUTO SW
GND
GND
GND
GND
TUBE LT
PC OUT
PC GND
PC IN
PWR SW
+5V
MODE SW
MUTE
INP SW
L RED
R RED
ORN 2
+5V
ORN 1
ORN 3
ORN 4
ORN 5
ORN 6
ORN 7
GRN
1
1
1
1
1
1
7
7
7
7
7
3
3
3
3
3
8
8
8
8
8
8
8
8
8
8
8
4.7µF
C58
4.75K
R84
R
4
3
DS1:1
AUTO OFF
DISABLED
INDICATOR

McIntosh C8AC Specifications

General

Brand	McIntosh
Model	C8AC
Category	Amplifier
Language	English