McIntosh MC275 Service Manual page 8

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