Panasonic GP 31 Service Manual

Technical Guide

Colour Television

GP 31 Chassis

Circuit Explanations

Panasonic

Kuala Lumpur Malaysia Sdn. Bhd.

Panasonic AVC Networks

Contents

Introduction 3 Location of Control & Circuit Boards 4 GP-31 Chassis Block Diagram 5

1. Tuning Circuit

1.1 Signal Processing 6

1.2 IF Control 6

2. Ultimate One Chip IC601

2.1 Features 8

2.2 IIC Bus 9

2.3 Memory IC 9

2.4 Reset Circuit 10

2.5 IC601 Pin Configuration 11

3. Video Circuit

3.1 Video Signal Processing 14

4. Audio Circuit

4.1 Audio Processor 17

4.1.1 Sound Processor 17

4.1.2 Audio Amplifier 17

5. Deflection Circuit

5.1 Horizontal Output Circuit 20

5.1.1 Horizontal Output Operation 21

5.2 Vertical Output Circuit 23

5.2.1 Vertical Output Operation 23

6. Colour Output

6.1 Colour Output Stage 24

7. Protection Circuit 25

8. Power Circuit

8.1 Start-up Circuit 29

8.2 Output Voltage Control 29

8.3 Regulation 30

8.4 Over Voltage Protection Circuit 30

8.5 Over Current Protection Circuit 31

8.6 Latch Circuit 31

8.7 Standby Operation 31

! WARNING

This service information is designed for experienced repair technicians only and is not designed for use by general public. It does not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product. Products powered by electricity should be serviced or repaired only by experienced professional technicians. Any attempt to service or repair the product or products dealt with in this service information by anyone else could result in serious injury or death.

Introduction

We at Panasonic realise that the service engineer needs to understand the circuitry

inside the TV and for this need, we have produced this Technical Guide.

This Technical Guide contains information for GP 31 chassis and should be used

in conjunction with the relevant Service Manuals for this chassis.

As the Technical Guide for the GP 31 chassis covers such a wide range of models,

some differences may occur in circuit descriptions and component references.

Location of Control & Circuit Boards

L-Board

A- Board

Board Name Function

A-Board Main Board

L-Board CRT Board

GP-31 Chassis Block Diagram

1. Tuning Circuit

Outline

The tuner is designed for reception of the conventional frequencies to date and the intermediate special channel frequencies. The IF stage of the tuner contains the video and audio demodulators which are designed for most widely used TV standards.

Fig 1.0

1.1 Signal Processing

1. The purpose of the tuner is to convert the VHF/ UHF TV broadcast signal (RF) into

intermediate frequency signal, IF (38.0MHz) [Fig 1.0].

2. The aerial intercepts the TV signal and amplified by the RF amplifier.

3. The local oscillator generates basic frequency to convert RF signal into IF signal

(intermediate signal) in the mixer.

4. Here the IF signals is output to UOC IC601 for video and sound processing.

1.2 IF Control

Control of internal Tuner-IF processing is performed by the UOC IC601, the IC601 sending control information via I²C bus input via pin 71 (SCL) and 72 (SDA).

In addition to this, AGC control of the Tuner-IF stage is controlled by the UOC via I²C. AFC information for Tuner-IF stage is fed back to the IC601 via control line AGC (pin 22).

UOC IC601

2. Ultimate One Chip IC601

Outline

The IC601 TDA959xN, also known as UOC, is a high-quality single chip TV processors IC which allow the economic integration of features in all classes of singlescan TV sets. UOC combine the functions of a video processor together with a microcontroller and teletext decoder.

The integrated microcontroller is supported by a powerful OSD generator with integrated Teletext & Close Caption acquisition including on-chip page memory.

2.1 Features

a. TV Processor

• Multi-standard vision IF circuit

• Picture improvement features with peaking black stretching

• Multi-standard colour decoder with automatic search system

• Internal base-band delay line

• Horizontal and vertical geometry processing

• OSD/text gain reduction control

• White point and black level off-set adjustment

b. Micro-controller

• 80C51 micro-controller core standard instruction set and timing

• 1 µs machine cycle

• 128K-byte ROM

• 12K-byte RAM

• Data Back-up

Storage of tuning, switching, control and adjustment data to the memory (IC1103) and reading out the data

• Switching and Control Output of the control signal for picture and sound, etc., and switching signal for TV/AV mode and so on

• Adjustment Output of adjustment levels for UOC (IC601) through I²C bus.

c. Teletext Decoder

• Text memory for 1 or 10 pages

• Automatic detection of FASTEXT transmission

• Data Capture for US Closed Caption

2.2 I²C bus

• The I²C bus is a two bus system consisting of a data line and a clock line.

• 5V is set for SDA / SCL. [Fig 2.0]

• Allow a large number of switching and control functions of GP-31 chassis.

The UOC IC601 generates bus signals which control the following hardware configuration.

1. EEPROM IC1103 These memories are 1K-byte, non-volatile memories of microchips, and bit pattern of 1024 x 8 bits.

2. Tuner TU001 To select a desired channel signal from the several RF signal from TV stations and

convert the selected RF signal into a signal of an intermediate frequency (IF).

3. Sound Processor IC2101

The sound processor IC will cover the sound processing of all analog TV-Standards worldwide, as well as the NICAM digital sound standards.

Fig 2.0

2.3 Memory IC

Fig 2.1

The memory IC1103 receives the data listed below as supplied from the UOC IC601 through I²C bus [Fig 2.1]. It is input or output whenever it is necessary. This memory IC is a non-volatile type, which data is maintained permanently although the power is cut off.

Last Memory Location

These memory locations will contain the following information that must be stored inside even if power to the EEPROM is interrupted.

1. 100 channels of BT voltage and band (VL, VH, U) information.

2. 100 channels of AFC, SKIP, COLOR SYSTEM and SIF information.

3. Last position for each switching mode.

4. Volume data.

5. TV/ AV1/ AV2 mode.

6. Recall ON/ OFF.

7. Power and auto off timer setting.

8. Service mode setting.

9. The COLOUR, NTSC TINT, BRIGHT, CONTRAST and SHARPNESS DAC data, and each SUB-DAC data, CUT-OFF, RGB-DRIVE etc.

10. PICTURE MENU & SOUND MENU.

11. AVL

Pin No. Name Function

1 A0 GROUND 2 A1 GROUND 3 A2 GROUND 4 GND GROUND 5 SDA Serial Data In/Out 6 SCL Serial Clock Input 7 WP Write Protect Input 8 VCC 5V

2.4 Reset circuit

1. Power on reset is generated internally to the UOC IC601; hence no external reset is required. (The TV processor generates the master reset in the system, which in turn will reset the micro-controller.)

2. During power ON operation, or during a momentary drop in the +B voltage, insufficient voltage supply to UOC IC601 may occur. Thus, there is a possibility that incorrect operation of the UOC occur.

3. In order to prevent incorrect operation, a resetting pulse is activated until the voltage fed to the UOC is normalized.

4. When the power switch is turned on, if the VDD of the UOC is less than 3.3V then UOC starts to reset.

5. UOC start to function again when VDD becomes more than 3.3V.

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