Service manual
2-35
March 2000
Part No. 001-3139-502
900 MHz RECEIVER SCHEMATIC
FIGURE 2-15
FOLDOUT
Q8
3051
R37
470
L25
C62
.01uF
C63
68
R56
47
C64
68
C65
4.7
CR14
R57
10k
C66
.01uF
TP4
R34
47k
R35
10k
Q4
3051
L18
R36
470
C73
.001uF
C71
22
C72
22
C70
.001uF
R38
47
R39
47k
R40
10k
Q5
3051
L19
R41
220
C77
10
C79
12
C81
12pF
R43
47
C80
470
+
C154
100uF
C78
.01uF
C82
470
C83
39
C84
62
C149
.01uF
C150
470
R42
10
+9V
R44
10k
R45
47k
C85
2
CR3
R46
10k
C87
.001uF
TP5
L20
L21
R47
220
C86
11
R48
270
C91
3
C90
10
C88
.01uF
C89
100
R49
47
Q6
3037
R50
10k
R51
47k
C93
10
C94
.001uF
R52
220
C92
39
Q7
3037
C95
.68
CR4
R53
10k
C97
100
TP6
L22
L23
L24
C96
2
BUFFER
FIRST
DOUBLER
SECOND
DOUBLER
THIRD
DOUBLER
FOURTH
DOUBLER
C10
9.1pF
L6
L7 L8
L9 L10
L11
C11
3.3
C12
9.1
C14
2200
R4
1.8k
R5
4.7k
Q1
3052
R6
430
C19
2200
C21
56
C24
56
C15
12
C27
.01
R8
10
R7
27k
L12
C17
9.1
C18
1.5
C25
15
L13
C26
7.5
Z1A
C28
2
L14
R9
100k
R12
2.7k
C29
.01
R11
10k
Q3
6009
T1
C30
20pF
R13
5.6k
C37
.01uF
C36
47
T2
3
2
4
1
1
2
3
4
5
10
U1
CA3012
C38
.1uF
C35
2200
R14
10
C34
.01
C39
82pF
C40
.01
R15
10
C41
.002uF
C33
4.7
Z2A Z2B
Z3B
R17
3.9k
C44
.01uF
T4
2
3
4
1
U2
CA3089E
C45
12pF
C49
.01uF
R19
2.2k
C48
2.7
T5
2
5
9
4
7
8
1
3
C43
.01uF
14
10
R20
4.7k
Z3A
Z5
L15
R22
3.3k
R23
330
R24
2.2k
C46
.1uF
R21
33
C47
.01uF
11
12
15 16
+13.8V
6
T3
1
43
2
R16
6.8k
TP2
TP3
13
C42
.01uF
R18
33k
TP1
R10
100
DOUBLER
HELICAL BANDPASS FILTER
FIRST MIXER
45 MHz CRYSTAL FILTER
SECOND MIXER
10.7 MHz CRYSTAL FILTER
IF AMPLIFIER
10.7 MHz CRYSTAL FILTER
DISCRIMINATOR
RAW DATA/AUDIO
C109
.1uF
R68
56k
C110
.0033uF
R70
20k
R69
56k
C111
220
U4B
3303
+
+4.5V
6
5
7
R71
10k
C112
.047uF
C113
.47uF
R72
100
U4C
3303
+
C115
.033uF
9
10
8
C114
.047uF
R73
1M
+4.5V
C116
.15uF
R74
100
U4D
3303
+
13
12
14
C117
.047uF
R75
1M
+4.5V
C118
.047uF
R76
10k
U4A
3303
+
2
3
1
+4.5V
R77
120k
C120
.01uF
J5
AUDIO
TEST
JACK
43
5
21
13
98
6
R79
10k
R80
10k
+9V
U5B
4066
U5A
4066
U5C
4066
LOW-PASS FITLER <3 kHz
HIGH-PASS FITLER >300 Hz DE-EMPHASIS
AUDIO GATING
RX AUDIO
SQUELCH ENABLE
(FROM LOGIC)
(TO LOGIC)
(TO LOGIC)
Q
Q
13
12
U10B
4013
C
D
9
11
R
10
S
8
C139
9.1
R95
10k
R96
10k
+9V
ANT 1 ANT 2
S1
ANTENNA SWITCH
TOGGLE FLIP-FLOP
C
3
5
D
S
6
R
4
CR9
R94
68k
C136
.01
U8A
4013
Q
Q
2
1
+9V
C135
9.1
U7C
3303
+
10
8
14
R93
100k
R92
100k
9
U7D
3303
+
R89
10k
CR5
CR7
CR6
CR8
C133
.01uF
U6A
3303
+
2
1
C140
9.1
R87
200k
R86
2.7k
C132
1800
U6B
3303
+
6
7
R84
330k
C130
100
C131
100
C129
100
R85
27k
J2
ANTENNA 1
C1
9.1
J3
ANTENNA 2
C3
9.1
R1
2.2k
C9
9.1
L2
L4
L5
C4
3.6
C2
3.6
C157
100
C5
9.1
R2
2.2k
L1
CR1
CR2
C7
9.1
C158
100
C6
9.1
R3
2.2k
L3
C8
9.1
13
123
5
DIVIRSITY SWITCH
1
10
14
R78
100k
+4.5V
+
C121
10uF
R81
10k
LOCAL
ON/OFF/VOL
7
+
C104
10
R58
18
+
C124
10uF
42
1
C123
33
5
C127
.047uF
C126
3300
+
C125
10uF
7
R83
100
6
C122
.1uF
+13.8V
+
C128
220uF
LS1
LOCAL SPEAKER
8 OHM
U7B
3303
+
6
7
5
C142
.01uF
R97
4.7k
R110
6.8k
RT2
8k
R98
12k
C136
.01uF
C143
.01uF
CR10
CR12
CR11
CR13
R99
10k
R100
10k
R101
47k
C145
.1uF
U7A
3303
+
R104
1M
R102
47k
C144
.1uF
2
1
3
U6D
3303
+
13
14
12
R103
330k
R105
100k
R106
100k
+
C146
1uF
U6C
3303
+
10
8
9
R108
470k
R107
2.2k
+
C147
1uF
R109
2.2k
+9V
5 (TO LOGIC)
PART OF J101 ASSEMBLY
+9V
+4.5V
+13.8V
SOURCE
SOURCE
SOURCE
U9
TBA820
12
2
+13.8V DC
AUDIO AMPLIFIER
TIMING BUFFER
SCHMITT TRIGGER
NOISE RECTIFIER
NOISE AMPLIFIER
NOISE SQUELCH CONTROL
NOISE AMPLIFIER
OUTPUT
HIGH-PASS FITLER >30 kHz
NOISE AMPLIFIER
NOISE RECTIFIER
COMPARATOR
ONE-SHOT
DIVERSITY ANTENNA CONTROL
RECEIVE AUDIO PROCESSING
NOTES:
1. ALL CAPACITORS ARE IN PICOFARADS AND ALL RESISTORS ARE IN OHMS
UNLESS OTHERWISE SPECIFIED.
2. IC CONNECTIONS NOT SHOWN:
U5, U7, U8
IC
PIN NUMBER
SUPPLY GND
14 7
U4, U6
411
LOGIC NOISE SQUELCH
R88
10k
R91
47k
R90
100k
SQUELCH
ADJUST
L28
Z1B
+9V
Q2
3051
C57
.022uF
R30
10k
R27
12k
L16
C50
91
Y2
17.150MHz
R29
2.7k
C51
300
R28
12k
C54
RT1
C56
43
C55
3.5-20
C59
5.6
L17
C58
75
C53
4.7
C52
75
C31
.1uF
+9V
R26
1k
IF IN
AC RET
DC BIAS
GND MUTE IN
GND
8
GND
IF OUT
IF IN
Vcc
V+
MUTE
OUT
AGC
OUT
NC
DC REF
BIAS
QUAD
IN
QUAD
OUT
AFC OUT
AUDIO OUT
TUNE OUT
R61
470
R32
47k
C61
.001uF
R33
10k
C60
100
L26
L27
J6
FROM
SYNTHESIZER
C100
.33
R31
51
J7
TO J202 ON
SYNTHESIZER
BOARD
3
4
2
1
J8
+9V
NC
NC
TO
SYNTHESIZER
OUT
GND GAIN
FREQ
COMP
BOOT
STRAP
Vcc
IN
C103
.1uF
R60
2.7
R59
10
C151
.01uF
C148
.1uF
C137
10
C134
.1uF
C141
.1uF
C138
.1uF
F1
2A
1
2
3
U3
78S09
+
C101
47uF
+
C99
100uF
R55
10k
R54
12k
+
C98
6.8uF