JVC VS-DT2000 Service Manual page 31

LA1838 (IC1) : FM AM IF amplifier & Detector, FM MPX Decoder
1. Terminal layout & Block diagram
30 29 28
REG
ALC
AM
OSC
AM
BUFF MIX
SD
COMP
FM
AM/FM
S-CLRVE
S-METER
IF-BUFF
PM
FM IF
DET
1 2
3
2. Pin function
Pin No. Symbol
1
FM IN
2
AM MIX
3
FM IF
4
AM IF
5
GND
6
TUNED
7
STEREO
8
VCC
9
FM DET
10
AM SD
11
FM VSM
12
AM VSM
13
MUTE/IFOUT
14
FM/AM
15
MONO/ST
16
LOUT
17
ROUT
18
LIN
19
RIN
20
RO
21
LO
22
MPX IN
23
FM OUT
24
AM DET
25
AM AGC
26
AFC
27
AM RF
28
REG
29
AM OSC
30
OSC BUFFER
27 26 25 24
FM
RF.AMP
AGC
AM IF DET
AM
S-METER
TUNING STEREO
DRIVE DRIVE
GND
5
4 6 7
I/O
I This is an input terminal of FM IF signal.
O This is an out put terminal for AM mixer.
I Bypass of FM IF
I Input of AM IF Signal.
- This is the device ground terminal.
O When the set is tunning,this terminal becomes "L".
O Stereo indicator output. Stereo "L", Mono: "H"
- This is the power supply terminal.
- FM detect transformer.
- This is a terminal of AM ceramic filter.
O Adjust FM SD sensitivity.
O Adjust AM SD sensitivity.
I/O When the signal of IF REQ of IC121(LC72131) appear, the signal of FM/AM IF output.
Muting control input.
I Change over the FM/AM input. "H" :FM, "L" : AM
O Stereo : "H", Mono: "L"
O Left channel signal output.
O Right channel signal output.
I Input terminal of the Left channel post AMP.
I Input terminal of the Right channel post AMP.
O Mpx Right channel signal output.
O Mpx Left channel signal output.
I Mpx input terminal
O FM detection output.
O AM detection output.
I This is an AGC voltage input terminal for AM.
- This is an output terminal of voltage for FM-AFC.
AM RF signal input.
I
O Register value between pin 26 and pin28 besides the frequency width of the input signal.
- This is a terminal of AM Local oscillation circuit.
O AM Local oscillation Signal output.
23 22 21 20 19
DECODER
ANIT-BIRDIE
P-DET
STEREO
5N
SW
FF
VCO FF
19k
384KHz 38k
VCC
8 9
10 11 12
Function
VS-DT2000
18
17 16
MUTE
FF
PILOT
/ 2 19k /LS
DET
13 14 15
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