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XR-1790
SERVICE MANUAL
US Model Canadian Model E Model

Model Name Using Similar Mechanism Tape Transport Mechanism Type

NEW MG-36SZ9-32

SPECIFICATIONS

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FM/AM CASSETTE CAR STEREO
MICROFILM

XR-1790
5-3. SCHEMATIC DIAGRAM ­ MAIN Section (1/2) ­ · See page 16 for Waveform.

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XR-1790
5-4. SCHEMATIC DIAGRAM ­ MAIN Section (2/2) ­ · See page 25 for IC Block Diagram.

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XR-1790
5-5. PRINTED WIRING BOARD ­ PANEL Section ­

(Page 17)

· Semiconductor Location
Ref. No. Location B-9 C-10 C-7 C-6 C-8 B-9 D4 D900 D901 D902 D903 IC900

5-6. SCHEMATIC DIAGRAM ­ PANEL Section ­

· Waveform
2 IC900 #TM (OSC) (Page 22)

2.2 Vp-p

15 µs

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· IC Block Diagram ­ MAIN Board ­ IC450 LC75372E
R10dBOUT RCT2 RT1 RCT1 RT2 R10dBIN RSELO RT3

RIN

33

32

31

30

29

28

27

26 25

24 23

ROUT 34

RVREF RVREF + ­

RVREF + ­ + ­

RVREF 22 R2 21 R1 20 TEST

RFIN 35 RFOUT 36 + ­ RVREF RVREF

R3 NC

RROUT 37

RVREF 38 VREF 39 LVREF 40 LVREF LROUT 41 + ­

LFOUT 42 LFIN 43

LVREF LVREF LOUT 44 + ­ LVREF LVREF

1

2

3

4

5

6

7

8 9

LT2

LT1

L10dBIN LSELO

LIN

L10dBOUT

LCT2

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LCT1

LT3

L3 NC

+ ­

+ ­

+ ­

+ ­

+ ­ 19 VSS 18 NC + ­ LATCH RVREF DECODER SHIFT REGISTER CONTROL 17 CL 16 DI 15 CE + ­ + ­ RVREF LVREF LVREF LVREF 14 VDD 13 L1 12 L2 10 11

5-7. IC PIN FUNCTION DESCRIPTION
· MAIN BOARD IC1 LC72322N-9400 (SYSTEM CONTROLLER) Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23, 24 25 26 27 28 29 30 31 32 33 34 35 36 to 40 41 42 43 44 Pin Name XIN TEST2 NC AM-SD FM-SD STEREO MOTOR AMP-MUTE2 MW/SW -- BEEP POWER-ON ILL-ON N/R TAPE-IN FF-REW K1 K0 AMP-ON SEEK SEEK LOCAL/DX -- T2 T1 T0 VOL-CE VOL-DI VOL-CL VDD MUTE-REQ BAND-KEY PANEL-IN NC -- MUTE -- AMP-MUTE ANT-REM I/O I I I I I I O O O O O O O I I I I I O O O O O O O O O O O -- I I I I O O O O O System clock input terminal (4.5 MHz) Connected to ground Not used (fixed at "H") AM signal meter voltage detection input from the FM/AM tuner unit (TU100) "H" active FM signal meter voltage detection input from the FM/AM tuner unit (TU100) "H" active Stereo detection signal input from the FM/AM tuner unit (TU100) (Commonly used for stereo display input) FM stereo detection at input of "L" Capstan/reel motor (M901) drive signal output "H": motor on Muting control signal output to the power amplifier (IC500) "L": muting on MW/SW selection signal output terminal "H": MW, "L": SW Not used (fixed at "H") Not used (open) Beep sound signal output terminal "H" active Power on/off control signal output "H": power on Power on/off control signal output for the liquid crystal display driver (IC900), illumination lamp and back light lamp "H": power on Tape direction switch (S901) input terminal "H": forward side, "L": reverse side Tape in detection switch (S903) input terminal "L": tape in FF/REW detection switch (S902) input terminal "L": FF/REW mode Key matrix return signal input terminal Not used (fixed at "L") Key matrix return signal input for the frequency select switch (S1) Used for the E model only Standby on/off signal output to the power amplifier (IC500) "L": standby, "H": amp on Seek control signal output to the FM/AM tuner unit (TU100) "H" active Used for the E model only Seek control signal output to the FM/AM tuner unit (TU100) "L" active Used for the US and Canadian models only Local/DX selection signal output to the FM/AM tuner unit (TU100) "L": DX, "H": local Not used (open) Key matrix scan signal output for the frequency select switch (S1) Used for the E model only Key matrix scan signal output terminal Not used (open) Chip enable signal output to the electrical volume (IC450) "H" active Serial data output to the electrical volume (IC450) "H" active Serial data transfer clock signal output to the electrical volume (IC450) Power supply terminal (+5V) Muting request signal input terminal ("H" active) "L": accessory on, "H": accessory off TUNER switch (S900) input terminal "L" is input when pressing the switch Detects the removal of the attaching and removing type front panel block "L": attaching Not used (open) Not used (fixed at "L") Not used (open) Audio muting on/off control signal output terminal "H": muting on Not used (open) Not used (open) Amp muting on/off control signal output terminal "L": muting on Not used (open) Control signal output for the external power antenna and external amplifier "H" active Function

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Pin No. 45 to 48 49 50 51 52 53 54 55 56 57 58 to 60 61 62 63 64, 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

Pin Name -- KS2 KS1 KS0 -- LCD-CLK LCD-CE LCD-DATA AM-ON MONO -- FM-ON TUNER-ON MW/LW -- NC CE RESET KEY-IN IFIN NC BU-CHECK VDD FMIN AMIN VSS EO -- TEST1 XOUT

I/O O O O O O O O O O O O O O O O I I I I I I I -- I I -- O O I O Not used (open) Key matrix scan signal output terminal Not used (open)

Function

Serial data transfer clock signal output to the liquid crystal display driver (IC900) Chip enable signal output to the liquid crystal display driver (IC900) Serial data output to the liquid crystal display driver (IC900) AM system power supply on/off control signal output terminal Not used (open) Not used (open) FM system power supply on/off control signal output terminal Tuner system power supply on/off control signal output terminal Not used (open) MW/LW selection signal output terminal Not used (open) Not used (fixed at "L") Accessory switch on/off detection signal input terminal "H": accessory on, "L": accessory off (hold mode) System reset signal input terminal "L": reset "L": MW, "H": LW "H": FM on "H": tuner on Not used (open) "H" active "H" active "H": AM on

Key matrix return signal input terminal (A/D input) FM and AM intermediate frequency detection signal input from the FM/AM tuner unit (TU100) Not used (fixed at "L") Battery detect signal input terminal Power supply terminal (+5V) FM local oscillator input from the FM/AM tuner unit (TU100) AM local oscillator input from the FM/AM tuner unit (TU100) Ground terminal Main charge-pump control signal output terminal Not used (open) Connected to ground System clock output terminal (4.5 MHz)

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