JVC MX-G950V Service Manual page 45

LA1838 (IC1): FM AM IF amp & detector, FM MPX decoder
1. Block Diagram
30 29 28
REG
AM
ALC AM
MIX
OSC
BUFF
SD
COMP
FM AM/FM
S-CLRVE
S-METER
IF-BUFF
PM
FM IF
DET
1 2
3
2. Pin Function
Pin
Symbol
I/O
No.
FM IN
I This is an input terminal of FM IF
1
signal.
AM MIX
2
O This is an out put terminal for AM
mixer.
3 I
FM IF Bypass of FM IF
AM IF
4 I Input of AM IF Signal.
5 GND
This is the device ground terminal.
6 TUNED
O When the set is tunning,this terminal
becomes "L".
STEREO
7 O
Stereo indicator output. Stereo "L",
Mono: "H"
8
VCC This is the power supply terminal.
9 FM DET FM detect transformer.
10 AM SD
This is a terminal of AM ceramic filter.
O
11 FM VSM Adjust FM SD sensitivity.
12 AM VSM O
Adjust AM SD sensitivity.
13 I/O
MUTE When the signal of IF REQ of IC121(
LC72131) appear, the signal of FM/AM
IF output. //Muting control input.
Change over the FM/AM input.
14
FM/AM I
"H" :FM, "L" : AM
MONO/ST O
Stereo : "H", Mono: "L"
15
27 26 25 24
FM
RF.AMP
AGC
DET
AM IF
AM
S-METER
TUNING STEREO
DRIVE DRIVE
GND
5
4 6 7
Function
23 22 21 20
DECODER
ANIT-BIRDIE
STEREO
P-DET
5N
SW
FF
VCO
38k
384KHz
VCC
8 9
10 11
Pin
I/O
Symbol
No.
16
L OUT O
Left channel signal output.
17 R OUT O Right channel signal output.
18 L IN Input terminal of the Left channel post
I
AMP.
Input terminal of the Right channel
I
19 R IN
post AMP.
Mpx Right channel signal output.
20 O
RO
21
LO O
Mpx Left channel signal output.
22 MPX IN I
Mpx input terminal
23
FM OUT O FM detection output.
AM detection output.
24
AM DET O
This is an AGC voltage input terminal
25 AM AGC I
for AM
This is an output terminal of voltage
26 AFC
for FM-AFC.
AM RF signal input.
27
AM RF I
REG Register value between pin 26 and pin28
28 O
besides the frequency width of the
input signal.
29 AM OSC This is a terminal of AM Local
oscillation circuit.
30 OSC BUFFER
AM Local oscillation Signal output.
O
MX-G950V/MX-G880V
MX-G850V/MX-G750V
18
19 17 16
MUTE
FF FF PILOT
/
19k 19k LS DET
2 /
12 13 14 15
Function
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