China Chassis VE01, Amstrad 20M3 Schematic

COLOR TELEVISION

SERVICE MANUAL

CHASSIS: - VE01

MODEL NO: - 1450KT, 2050KT, 2150KT

CONTENTS

Safety Precautions------------------------------------------------------------------------ 3 Introduction----------------------------------------------------------------------------------- 3

1. SCART details------------------------------------------------------------------------------ 4

2. Micro-Controller and Small Signal function Æ TDA9351.------------------------ 5-8

3. Tuner------------------------------------------------------------------------------------------ 9

4. Video SwitchÆ HEF4052BP------------------------------------------------------------ 10

5. Sound Processor -ÆTDA9859--------------------------------------------------------- 10

6. Sound Output -ÆAN17821-------------------------------------------------------------- 10

7. Vertical Output Stage Æ STV9302A-------------------------------------------------- 10

8. Video Output Amplifier ------------------------------------------------------------------- 11

9. Power Supply------------------------------------------------------------------------------- 11

10. Memory IC Æ AT24C16---------------------------------------------------------------- 11

11. IC Description with Pin Details----------------------------------------------------- 12

11A. TDA9351------------------------------------------------------------------------- 12-18

11B. HEF4052BP--------------------------------------------------------------------- 18-19

11C. STV9302A----------------------------------------------------------------------- 19-20

11D. IC AT24C16--------------------------------------------------------------------- 20-21

11E. TDA9859------------------------------------------------------------------------- 21-23

11F. AN17821-------------------------------------------------------------------------- 24

11G.STR5Q0765----------------------------------------------------------------------- 24-25

11H. Video Amplifier Transistors--------------------------------------------------- 25-26

12. Alignment Procedures------------------------------------------------------------------ 26

12.A. Procedure to enter Service Mode------------------------------------------ 26

12.B. Procedure to enter Design Mode------------------------------------------- 26

12.C. White Balance Adjustment--------------------------------------------------- 27

12.D. Screen Adjustment------------------------------------------------------------- 27

12.E. Design and Service data adjustment-------------------------------------- 27-31

12.F. Manufacturing and alignment procedures-------------------------------- 32-42

13. Block Diagram-------------------------------------------------------------------------- 43

14. Circuit Diagram------------------------------------------------------------------------- 44

15. Track Side Layout--------------------------------------------------------------------- 45

SAFETY PRECAUTIONS

• Do not change any module unless the set is switched off.

• The mains supply side of the SMPS transformer is live. Use an isolating transformer

• Servicing of the CTV set should only be carried out by qualified person.

• Components marked with warning symbol on circuit diagram are critical for safety and

must only be replaced with an identical component

• Power resistor and fusable resistors must be mounted in an identical manner to the

original component.

• Discharge the capacitors like Main Filter when working on these.

• Do not solder when the set is on.

• Do not connect any external device like Speakers etc. when the set is on.

• When any signals are to be connected/ disconnected switch off the set.

• Wear rubber shoes/non-conducting so that your body does not become a passage for

electric current.

INTRODUCTION:-

VE01 chassis is capable of driving 14”, 20”, 21”, 21”PF tubes at appropriate currents. This

chassis is capable of working in the PAL / SECAM / NTSC systems. The sound system is

capable of giving 1.5W r.m.s. output into a load 8E speaker. One page simple TELETEXT,

TOPTEXT and FASTEXT is provided. The chassis is equipped with 21 pin scart connector which

can accept via scart the SVHS format from VCRs.

The details of various sections with IC details and pin voltages are covered in this manual. The

alignment procedure in field and also at manufacturing line is also covered in detail. The block

diagram, circuit diagram and track side layout of VE01 chassis is also attached in this manual for

easy reference.

1. PERI- TV SOCKET (SCART)

PIN DETAILS OF SCART

Pin Name Description Signal Level Impedance

1 AOR Audio Out Right 0.5 V rms <1k ohm

2 AIR Audio In Right 0.5 V rms >10k ohm

3 AOL Audio Out Left + Mono 0.5 V rms <1k ohm

4 AGND Audio Ground

5 B GND RGB Blue Ground

6 AIL Audio In Left + Mono 0.5 V rms >10k ohm

7 B RGB Blue In 0.7 V 75 ohm

8 SWTCH Audio/RGB switch / 16:9

9 G GND RGB Green Ground

10 CLKOUT Data 2: Clockpulse Out Unavailable

11 G RGB Green In 0.7 V 75 ohm

12 DATA Data 1: Data Out Unavailable

13 R GND RGB Red Ground

0-2 V=TV, 5-8 V=WideScreen, 9.5-12 V=AV Mode

>10 kohm

14 DATAGND Data Ground

15 R

16 BLNK Blanking Signal 1-3 V=RGB, 0-0.4 V=Composite 75 ohm

17 VGND Composite Video Ground

18 BLNKGND Blanking Signal Ground

19 VOUT Composite Video Out 1 V 75 ohm

20 VIN

21 SHIELD Ground/Shield (Chassis)

RGB Red In / Chrominance

Composite Video In / Luminance

0.7 V (Chroma.: 0.3 V burst) 75 ohm

1 V 75 ohm

2. MICRO CONTROLLER AND SMALL SIGNAL FUNCTION WITH TDA 9351

combination of microcontroller and chroma (Small Signal function). This IC performs all important

functions in TV receiver. The details of IC are bifurcated in two parts. Small Signal function and

microcontroller

:- This IC is a

2A:- SMALL SIGNAL FUNCTION:

2A.1: VISION IF AMPLIFIER: The vision IF amplifier can demodulate signals with positive and

negative modulation. The PLL demodulator is completely alignment-free. The VCO of the PLL

circuit is internal, and the frequency is fixed to the required value by using the clock frequency

of the Controller/ Teletext decoder as a reference. The setting of the various frequencies (38,

38.9, 45.75 and 58.75 MHz) can be made via the control bits IFA-IFC in sub address 27H.

Because of the internal VCO, the IF circuit has a high immunity to EMC interferences.

2A.2: VIDEO SWITCHES:

The selected CVBS signal can be supplied to pin 38, the IF video output. The selection

The video switch has one input for an external CVBS or Y/C signal.

between both signals is realized by means of the SVO bit in sub address 22H. The video ident

circuit can be connected to the incoming ‘internal’ video signal or to the selected signal. This

ident circuit is independent of the synchronisation and can be used to switch the time-constant

of the horizontal PLL depending on the presence of a video signal (via the VID bit). Because of

the availability of the Y/C input and the subcarrier output an external comb-filter can be applied.

In that case an external video switch (or comb-filter with integrated switch) must be used. The

subcarrier output is combined with a 3-level output switch (0 V, 4 V and 8 V). The output level

and the availability of the subcarrier signal is controlled by the CMB1 and CMB0 bits. The

output can be used to switch sound traps etc.

2A.3: SOUND CIRCUIT (QSS VERSION)

The sound IF amplifier is similar to the vision IF amplifier and has an external AGC decoupling

capacitor. The single reference QSS mixer is realised by a multiplier. In this multiplier the SIF

signal is converted to the intercarrier frequency by mixing it with the regenerated picture carrier

from the VCO. The mixer output signal is supplied to the output via a high-pass filter for

attenuation of the residual video signals. With this system a high performance hi-fi stereo

sound processing can be achieved. The AM sound demodulator is realised by a multiplier. The

modulated sound IF signal is multiplied in phase with the limited SIF signal. The demodulator

output signal is supplied to the output via a low-pass filter for attenuation of the carrier

harmonics. The AM signal is supplied to the output (pin 44) via the volume control. It is possible

to get the AM output signal (not controlled on amplitude) on the QSS intercarrier output. The

selection is made by means of the AM bit in subaddress 29H. Another possibility is that pin 35

is transferred to external audio input pin and pin 32 to (non-controlled) AM output pin. This can

be realised by means of the setting the control bits CMB0 and CMB1 in subaddress 22H.

2A.4: FM DEMODULATOR AND AUDIO AMPLIFIER (MONO VERSIONS):-

demodulator is realised as narrow-band PLL with external loop filter, which provides the

necessary selectivity without using an external band-pass filter. To obtain a good selectivity a

linear phase detector and constant input signal amplitude are required. For this reason the

intercarrier signal is internally supplied to the demodulator via a gain controlled amplifier and

AGC circuit. The nominal frequency of the demodulator is tuned to the required frequency

(4.5/5.5/6.0/6.5 MHz) by means of a calibration circuit which uses the clock frequency of the

Controller/Teletext decoder as a reference. The setting to the wanted frequency is realised by

means of the control bits FMA and FMB in control byte 29H. When required an external sound

band-pass filter can be inserted in front of the narrow-band PLL. In that case pin 32 has to be

switched to sound IF input by means of the bits SIF (subaddress 21H) and CMB0/CMB1

(subaddress 22H). When the sound IF input is selected the subcarrier output or AVL function

are not available. From the output status bytes it can be read whether the PLL frequency is

inside or outside the window and whether the PLL is in lock or not. With this information it is

possible to make an automatic search system for the incoming sound frequency. This can be

The FM

realised by means of a software loop which switches the demodulator to the various

frequencies and then select the frequency on which a lock condition has been found. The

deemphasis output signal amplitude is independent of the TV standard and has the same value

for a frequency deviation of 25 kHz at the 4.5 MHz standard and for a deviation of 50 Khz for

the other standards. The audio control circuit contains an audio switch and volume control. In

the mono intercarrier sound versions, the Automatic Volume Levelling (AVL) function can be

activated. The pin to which the external capacitor has to be connected depends on the IC

version. For the 90 degree types the capacitor is connected to the EW output pin (pin 20). For

the 110 degree types a choice must be made between the AVL function and a sub-carrier

output for comb filter applications. This choice is made via the CBM0 and CMB1bits (in

subaddress 22H). When the AVL is active it automatically stabilises the audio output signal to a

certain level. The signal on the deemphasis pin (28) can be supplied to the SCART connector

via a buffer stage. It is also possible to use this pin as additional audio input. In that case the

internal signal must, of course, be switched off. This can be realised by means of the sound

mute bit (SM in subaddress 29H). When the IF circuit is switched to positive modulation the

internal signal on the deemphasis pin is automatically muted. The audio switch is controlled by

means of the INA/INB bits in subaddress 22H. It is, however, also possible to overrule the

audio switch position by means of the ADS and ADX bits (subaddresses 28H and 21H

respectively).

2A.5: SYNCHRONISATION CIRCUIT :-

and vertical sync pulses and a data-slicing circuit which extracts the digital teletext data from

the analog signal. The horizontal drive signal is obtained from an internal VCO which is running

at a frequency of 25 MHz. This oscillator is stabilised to this frequency by using a 12 MHz

signal coming from the reference oscillator of the micro controller/Teletext decoder. The

horizontal drive is switched on and off via the soft start/stop procedure. This function is realised

by means of variation of the T ON of the horizontal drive pulses. In addition the horizontal drive

circuit has a ‘low-power start-up’ function. The vertical synchronisation is realised by means of

a divider circuit. The vertical ramp generator needs an external resistor and capacitor. For the

vertical drive a differential output current is available. The outputs must be DC coupled to the

vertical output stage. In the types which are intended for 90 degree picture tubes the following

geometry parameters can be adjusted:

• Horizontal shift

• Vertical amplitude

• Vertical slope

The IC contains separator circuits for the horizontal

• S-correction

• Vertical shift

The types which are intended to be used in combination with 110 degree picture tubes have an

East-West control circuit in stead of the AVL function.

The additional controls for these types are:

• EW width

• EW parabola width

• EW upper and lower corner parabola correction

• EW trapezium correction

• Vertical zoom

2A.6: CHROMA AND LUMINANCE PROCESSING: -

(including the SECAM cloche filter) are realised by means of gyrators and are tuned to the right

frequency by comparing the tuning frequency with the reference frequency of the colour

decoder. The luminance delay line and the delay cells for the peaking circuit are also realised

with gyrators. The circuit contains a black stretcher function which corrects the black level for

incoming signals which have a difference between the black level and the blanking level.

2A.7: COLOUR DECODER :-

PAL/NTSC decoder does not need external reference crystals but has an internal clock

generator which is stabilised to the required frequency by using the 12 MHz clock signal from

the reference oscillator of the micro controller/Teletext decoder. Under bad-signal conditions

(e.g. VCR-playback in feature mode), it may occur that the colour killer is activated although

the colour PLL is still in lock. When this killing action is not wanted it is possible to overrule the

colour killer by forcing the colour decoder to the required standard and to activate the FCO-bit

(Forced Colour On) in subaddress 21H. The Automatic Colour Limiting (ACL) circuit

The IC can decode PAL, NTSC and SECAM signals. The

The chroma band-pass and trap circuits

(switchable via the ACL bit in subaddress 20H) prevents that over saturation occurs when

signals with a high chroma-to-burst ratio are received. The ACL circuit is designed such that it

only reduces the chroma signal and not the burst signal. This has the advantage that the colour

sensitivity is not affected by this function. The SECAM decoder contains an auto-calibrating

PLL demodulator which has two references, viz: the divided 12 MHz reference frequency

(obtained from the microcontroller) which is used to tune the PLL to the desired free-running

frequency and the bandgap reference to obtain the correct absolute value of the output signal.

The VCO of the PLL is calibrated during each vertical blanking period, when the IC is in search

or SECAM mode. The base-band delay line (TDA 4665 function) is integrated. This delay line

is also active during NTSC to obtain a good suppression of cross colour effects. The

demodulated colour difference signals are internally supplied to the delay line.

RGB OUTPUT CIRCUIT AND BLACK-CURRENT STABILIZATION : In the RGB control

2A.8:

circuit the signal is controlled on contrast, brightness and saturation. The ICs have a linear

input for external RGB signals. It is possible to use this input for the insertion of YUV signals.

Switching between RGB and YUV can be realised via the YUV-bit in subaddress 2BH. The

signals for OSD and text are internally supplied to the control circuit. The output signal has an

amplitude of about 2 Volts black-to-white at nominal input signals and nominal settings of the

various controls. To obtain an accurate biasing of the picture tube the ‘Continuous Cathode

Calibration’ system has been included in these ICs. A black level offset can be made with

respect to the level which is generated by the black current stabilization system. In this way

different colour temperatures can be obtained for the bright and the dark part of the picture.

The black current stabilization system checks the output level of the 3 channels and indicates

whether the black level of the highest output is in a certain window (WBC-bit) or below or

above this window (HBC-bit). This indication can be read from the status byte 01 and can be

used for automatic adjustment of the Vg2 voltage during the production of the TV receiver.

During switch-off of the TV receiver a fixed beam current is generated by the black current

control circuit. This current ensures that the picture tube capacitance is discharged. During the

switch-off period the vertical deflection is placed in an overscan position so that the discharge

is not visible on the screen.

2B. - MICROCONTROLLER WITH TELETEX DECODER: -

with embedded microcontroller is a control system designed for TV sets with analogue picture

and sound control. The system also offers an on screen display (OSD) and IR remote control of

all functions.

3. TUNER: tuning is based on frequency synthesis tunning.

GDC Tuner EWT 5F3T1 is controlled by I2C bus through IC TDA 9361.The

The integrated teletex decoder

CHANNEL COVERAGE : BAND

CHANEL RANGE

LOW BAND E2- S9 48.25 – 161.25

MID BAND S10 – S41 168.25 – 463.25

HIGH BAND E21 – E69 471.25 – 855.25

4. VIDEO SWITCH BU 4052

main function of this device is to accept an AV input from SCART, external AV and switch the

required output at pin no Z which is applied to small signal processing IC.

5. SOUND PROCESSOR

The TDA 9859 selects signal from Three Stereo Sources or Six Mono Sources and out put

can be given to scart. The sound processor is I2C bus controlled and all settings of bus are

: TDA 9859 is designed to perform demodulation of FM TV sound.

OFF AIR CHANELS

FREQUENCY

: The HEF4052 is a dual four channel analog multiplexer. The

( IN MHZ)

stored in sub address register.

6. SOUND OUTPUT

It is supplied by 13 volts from the 13 volt DC coming from a separate winding in the SMPS

transformer. An out power of 1.5 Watt can be delivered into an 8 Ohm Load. This IC is also

having a feature of auto volume controller. Similarly stand by signal coming from

microcontroller is used to disable the sound out put from speaker.

7. VERTICLE OUTPUT STAGE

for 90 degree and 110 degree deflection systems . One supply voltage for the scan is

required. The drive voltage is amplified by an amplifier. The supply voltage of this IC is 15

Volts.

8. VIDEO OUTPUT AMPLIFIER

output amplifier section. IC TDA6107 or transistorized circuit can be used for video signal

: - IC AN17821 is used as the AF out amplifier for the Stereo application.

:- The STV 9302 is a vertical deflection circuit can be used

: The RBG output signal from TDA 9351 is applied to video

amplification and to be applied to cathodes of CRT for generation of R, G, and B colors. If IC

is used, then internal amplifiers are used to amplify the video signal. The transistorized

amplifier can be designed by using transistor circuit in which 9 transistors are used. Chassis

VE01 consist of transistorized video amplifier circuit.

9. POWER SUPPLY

SMPS transformer controlled by STR 0765, which is designed for deriving, controlling and

protecting switiching transistor of SMPS. The transformer produces 110 volts for FBT, 13 Volt

for audio O/p IC, 33 Volts for tuner and 5 and 8 Volts regulated voltages through IC TA7805

and TA7808.

10. MEMORY IC

EEPROM organized as 128 pages X 16 bytes. This is compatible with I2C standards, two

wire serial interface which uses a bi directional data bus and serial clock.

: The DC Voltages required at various part of the chassis are applied by

: The 24C16 is a 16 Kilo Bit electrically erasable programmable memory.

11. IC DISCRIPTION AND PIN DETAILS

• TDA 9351Æ TV Signal processor- Teletex decoder with embedded microcontroller

• HEF 4052BP-Æ Video Switch

• STV 9302-Æ Vertical Deflection Output

• 24C16-Æ Memory IC

• TDA 9859-Æ Sound Processor

• AN 17821-Æ Sound Output

• KA 5Q0765-Æ STR

• Video amplifier.

11A. TDA 9351:-

microcontroller and US Closed Caption decoder. The IC is used in television receivers with

90degree and 110 degree picture tubes. The ICs have supply voltages of 8 V and 3.3 V and

they are mounted in S-DIP envelope with 64 pins. This IC is having higher degree of

integration because delay line with adjustable delay time, PAL / SECAM / NTSC decoder has

been integrated. In addition to this some special features like Continuous Cathode

Calibration’, white point and black level offset, AVL are added in this version. As this is a

combination of microcontroller and TV signal processor, the features of IC are divided in two

sections

TV Signal processor Important Features

• Internal (switchable) time-constant for the IF-AGC circuit.

• A choice can be made between versions with mono intercarrier sound FM

demodulator and versions with QSS IF amplifier.

• The mono intercarrier sound versions have a selective FM-PLL demodulator which

This IC is the functions of a TV signal processor together with a

can be switched to the different FM sound frequencies (4.5/5.5/6.0/6.5 MHz).The

quality of this system is such that the external band-pass filters can be omitted.

• Source selection between ‘internal’ CVBS and external CVBS or Y/C signals

• Integrated chrominance trap circuit

• Integrated luminance delay line with adjustable delay time

• Asymmetrical ‘delay line type’ peaking in the luminance channel

• Black stretching for non-standard luminance signals

+ 28 hidden pages