Casio TV-1750I, TV-1750N Service manual

(with price)

INDEX

POCKET TELEVISION

TV-1750I TV-1750N

JULY. 1994

Page

Specifications.............................................................................................2

Block Diagram ...........................................................................................3

Circuit Operations......................................................................................4

Adjustment

Linear PCB..........................................................................................5

Printed Circuit Boards................................................................................9

Electrical Parts List ..................................................................................11

Mechanical Parts List...............................................................................17

Exploded View / Disassembly..................................................................18

Wiring Diagram........................................................................................19

Schematic Diagrams and Waveforms .....................................................20

SPECIFICATIONS

Item Specification

VHF UHF

Reception Channels TV-1750N 2 ~ 12 ch 21 ~ 69 ch

TV-1750I A ~ H2 ch 21 ~ 69 ch

Power Voltage DC 6.0 V

Power Consumption Approx. 3.6 W

Current Consumption Approx. 600 mA

Battery Life (with alkaline batteries) Approx. 2.5 hours

Batteries : 4 AA size batteries

Power Supply Car adaptor : CA-K65

AC adaptor : AD-K65

Connection Terminals Earphone jack : 3.5ø mini

External power jack : 6.0 V DC IN

Screen Size 2.5 inches

No. of Picture Element 118,800 (220 × 540) dots

Dimensions 135.5 mm (H) × 91 mm (W) × 38.1 mm (D)

Weight 240 g excluding batteries

8.5 oz excluding batteries

Options AC adaptor : AD-K65

Car adaptor : CA-K65

Body Color Black

— 2 —

Antenna

BLOCK DIAGRAM

Power Supply

1 TU200 2 Q200

IF Amp.Tuner

IC500

Tuning Voltage Generator

VCC2 (3.95V) VCC7 (41.6~51.6V) VEE1 (-6.5~-8.0V)

VR800

Brightness Control

3 IC200

Video Sound Det. FM AFT Circuit AGC Circuit

Osc. Display Control A-D Converter Auto-Tuning Control

8 Q800~Q806

Det

IC300

Chroma Circuit

IC700

Display Voltage Generator

VR600

Volume Control

4 IC600 Speaker

Audio Amp.

Common Driver

LCD

Segment Driver

1 — Color Tuner: TU200 TEPE5-01

Selects a desired radio wave and changes it to the video IF signal.

2 — Video IF Amp.: Q200 2SC4238

Amplifies the video IF signal output from the tuner TU by 10 times (20 dB).

3 — Video Det./Sound Det./FM Det./AFT/AGC: IC200 M51348FP

Eliminates the carrier wave in the video IF signal, and picks up the video signal and the sound IF signal. Also, the sound signal is picked up from the sound IF signal by FM detection.

4 — Audio Amp.: IC600 NJM2070M

Sound amplification.

5 — Chroma Circuit: IC300 M52045FP

Generates the tricolor (red, green, and blue) from the video signal.

6 — OSC/A-D Converter/Display Control/ Auto-Tuning Control : IC700 MSM662501 GSK-640E

Converts the color signal into a digital signal. Also, generates the clock pulse for the display and controls the display.

7 — Tuning Voltage Generator: IC500 MSC1169MS-K

Generates the tuning voltage with the tuning pulse (TU) output from 6.

8 — Display Voltage Generator: IC800 BA10358F, Q804 ~ Q806 Q810 Q811 2SD1149S,

2SD601A-R×3, 2SB709A-R Generates the display voltages V0 ~ V4 with VEE1 and VCC7 outputs from the power supply.

— 3 —

AD2 AD1

RLL

VDD2

RHH

M7 M8 M9

M10

PSi

VSS1

IC700

B G R

VSS2 TE1

A/D

Mode

Control

Data Output

CIRCUIT OPERATIONS

TE2

TE4

TE5

TE6

M6 M5 M4 M3 M2 M1 AFT

Frequency

Divider

Channel bar Control

Vertical

positioning

Control

TE3

Test Control Mode Control

Test

Circuit

Display Control

Sweep

Control

Tuning Control

Tuning Voltage UP/DOWN Counter

Pulse Width Modulation D/A

Horizontal

positioning

Control

AFT

Control

Phase

Comparator

Frequency

Divider

Key

Switch

Control

Mute

Control

Synchronism

Judgment

Frequency

Separator

Oscillator

KDB KCB AVB UHF

MTB

VLB

VDD1 C-S PD

OSC1 OSC2

D1 D2 D3 D4 D5 D6 CDB CFB CNB ECB

Signal Name

Function

SCB STB HDB CK1 CK2

SNB

Signal Name

Function

D1 ~ D6 Display data output terminal MTB Mute control terminal

SNB Data latch signal TU Tuning control pulse output terminal CDB Scanning start signal VLB VHF High/Low channel select signal

output terminal CFB Output voltage changeover signal UHF VHF/UHF select signal CNB Scanning signal shift lock signal AVB

KCB Key input terminal KDB

SCB Brightness modulation pulse control AFT AFT voltage input terminal

STB Sampling start signal M1 ~ M10 Mode select signal input terminal

ECB Signal input terminal controlling the

TE1 ~ TE6

Test terminal

segment drive terminal to "H" during no display

CK1, CK2 Clock pulse output terminal R, G, B Original color

OSC1 Oscillator freuency control terminal RLL "L" level voltage input terminal of OSC2 video signal

PD Clock pulse adjustment terminal RHH "H" level voltage input terminal of

video signal

C-S Synchronizing pulse input terminal PS1 Mode control signal

HDB Horizontal synchronizing signal input VSS1 Power supply voltage input terminal

terminal

VDD1 VDD voltage input terminal

— 4 —

ADJUSTMENT

Linear PCB

1) Items to Be Adjusted Item Measuring Instrument

VCC2 voltage setting Voltmeter Video detection coil adjustment TV signal generator, pattern generator, oscilloscope,

low-pass filter AFT coil adjustment Sweep generator, oscilloscope, voltmeter Contrast adjustment TV signal generator, pattern generator, oscilloscope AGC adjustment TV signal generator, pattern generator, IF levelmeter Clock adjustment Voltmeter

2) Adjustment and Test Point Locations TOP VIEW

TP1

T201

T200

— 5 —

BOTTOM VIEW

TP3

TP6

Pad IF

VR200

VR700

TP2

TP4

TP5

TP7

VR100

VR300

3) Equipment Connection / Procedure

VCC2 Voltage Setting

TV-1750

Set

Voltmeter

Output

TP1

Input Input Input Output Output

Connection Point Signal Connection Point

Adjust Result

VR100

Voltmeter

TP1

Adjust for 4.30 ± 0.02V reading on voltmeter.

— 6 —

* Open soldering pad IF.

Pattern generator

Signal generator

Video Detection Coil Adjustment

TV-1750

Set

Input Output

TP2

TP3

Oscilloscope

Low-pass filter

Input Input Input Output Output

Connection Point Signal Connection Point

Pattern generator

Signal generator

Color bar

38.9MHz

TP2 T200 TP3

40±3dBµ

Adjust Result

Low-pass filter Oscilloscope

AFT Coil Adjustment

* Open soldering pad IF.

Sweep generator

Input

TP2

TV-1750

Set

Oscilloscope Voltmeter

Output

TP4

38.9±5MHz

Sweep generator

TP2 T201 TP4

(Sweep)

Maker:

38.9MHz

Voltmeter Oscilloscope

70dBµ

Adjust for DC level at mini-

Adjust for 2.0 ± 0.2V reading on voltmeter. Confirm that the marker is at the middle of S-curve on oscilloscope.

* Open soldering pad IF.

Pattern generator

Signal generator

Color bar

38.9MHz

TP2 VR300 TP5

70dBµ

Contrast Adjustment

Signal generator

Oscilloscope

— 7 —

TV-1750

Set Oscilloscope

Input Output

TP2

TP5

Adjust step form wave to read

0.90 ± 0.05 Vp-p.

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