Toshiba MM20E45 Service Manual

FILE NO.016-9502

TECHNICAL TRAINING MANUAL

COLOUR TELEVISION

N5MM1 Chassis

MM20E45

CONTENTS

SECTION I OUTLINE

SECTION II CHANNEL SELECTION CIRCUIT

SECTION III RGB SIGNAL PROCESSING CIRCUIT

SECTION IV CRT DRIVE CIRCUIT

SECTION V MODE DISCRIMINATING CIRCUIT AND SYNC SIGNAL PROCESSING CIRCUIT

SECTION VI SYNC SEPARATION CIRCUIT OF TV MODE

SECTION VII HORIZONTAL AND VERTICAL OSCILLATION CIRCUIT

SECTION VIII VERTICAL DEFLECTION CIRCUIT

SECTION IX HORIZONTAL DEFLECTION CIRCUIT

SECTION X PROTECTION CIRCUIT

SECTION XI OSD STABILIZATION CIRCUIT

SECTION XII PICTURE TUBE

SECTION XIII POWER SUPPLY CIRCUIT

SECTION XIV FAILURE DIAGNOSIS PROCEDURES

SECTION I OUTLINE

1. OUTLINE OF N5MM1 CHASSIS (MM20E45)

This model is a 20” color TV with 181 channel tuner and built in VGA and Mac II capability. The hybrid design of this model allows it to serve several purposes. Television reception, a monitor running Multimedia, PC applications, or for playback of video games. The 20” FST picture tube features a stripe pitch 0.58mm, providing a favourable comparisons to conventional designs which generally measure

0.75 to 0.9mm.

2. PC BOARD CONFIGURATION

(1) Power/V.C.D. PB5226

PB5226-1 Power PB5226-2 V.C.D.

(2) Deflection PB5227

(3) Signal/Video PB5228

PB5228-1 Signal PB5228-2 Video PB5228-3 D-SUB

1-1

Converter trans

Front keys

Power LED

Remote control receiver

3. CONSTRUCTION OF CHASSIS

Choke coils

V out radiator

Choke trnas

Video unit

Flyback trans

D-sub unit

1-2

Power unit

Converter trans

Rectifier

Power radiator

Stand by trans

Sound out radiator

Def unit

V/C/D unit

Tuner

Jack board

S-VIDEO

H out radiator

Signal unit

D-sub connector

4. LOCATION OF CONTROLS

4-1 TV Set

RGB/

TV/VIDEO

button

MENU button

ADV button

VOLUME

CHANNEL

POWER indicator

REMOTE senser

POWER button

1-3

4-2 Remote Control

This Remote Control allows you to control the functions of your TV set from 16 feet (5m) away. The “*” marked function buttons do not have duplicate locations on your TV set. They can be controlled only by the Remote Control.

Aim at the TV set

TIMER button*

RECALL button*

V/VIDEO button

Channel Number buttons*

CH RTN (Channel Return) button*

PIC (Picture)* button

RESET button*

AUD (Audio) button*

MTS button*

POWER button

MUTE button

VOLUME buttons

CHANNEL button

SET UP button*

-/+ buttons

OPTION button*

1-4

4-3 Monitor Panel

This TV set is equipped with RGB INPUT connector, RGB AUDIO INPUT jacks, S-VIDEO INPUT jack, VIDEO/AUDIO INPUT jacks and VARIABLE AUDIO OUTPUT jacks of connecting your desired personal computer and video/audio equipment.

TV Rear

RGB INPUT Connector – provide for direct connection of a personal computer.

RGB AUDIO INPUT Jacks – provide for direct connection of a personal computer with audio output terminals.

S-VIDEO INPUT Jack – provide for direct S-video connection from an S VHS VCR or a video disc player.

VIDEO/AUDIO INPUT Jacks – provide for direct connection of video devices (VCR, video disc player, camcorder, etc.)

with video/audio outputs.

VARIABLE AUDIO OUTPUT Jacks – feed volume-controlled stereo audio out from whatever displayed on the screen, allows connection of audio amplifier and lets you adjust sound level with TV’s remote.

1-5

5. MM20E45 BLOCK DIAGRAM

VAR. OUT

VIDEO

(VERT)

(+15V)

(HEATER)

capacitor

switching

Resonance

Drive

switching

output

Horizontal

Signal

switching

AN5862K

RGB

TA7730

Signal switching

RGB

FBT

G-output

B-output

R-output

output

Horizontal

OSD

LA7837

Vertical output

R-Y G-Y B-Y -Y

Horizontal drive

V/C/D

TA8801

Linear coil

switching

S-shape

capacitor

switching

DPC

TA8859AP

High voltage

control chopper

Horizontal/vertical

oscillation LA7860

capacitor

switching

Resonance

Drive

switching

F/V conversion

Horizontal drive

control chopper

Horizontal amplitude

IR9331

20VMMTV BLOCK DIAGRAM

D.L

TC4053BP

Signal switching

RGB

Tuner/IF module

VIDEO

Band

pass

TA8200AH

Audio output

CXA1774S

Audio control

1-6

C. CAP slicer

Micro-computer

Mode distinction

TA75339AP

TC74HC86AP

TC4514P

TA75902

Synchronizing signal

process M52346SP

H.Sync

DAC

Memory

V.Sync

Syncon G

TC40538P

Synchronizing

signal switching

+15V

HEATER

Power unit

To be added

for MM

TV & MM

AUDIO

VERT.

+100V

Model change

( ) For MM

6. SPECIFICATIONS

SPECIFICATIONS

GENERAL

10 Local Keys 8key 11 Front Surround –

SOUND

PICTURE

OTHER

TERM

CABINET

12 Sub Bass System 13 Audio Output 5W x 2 14 Speaker Size & Nbr 80 x 120 x 2 15 Comb Filter (GLS) 16 Black Level Expand – 17 Horizontal Resolution 500 18 Parental-Ch Lock 19 Channel Caption – 20 Off Timer (180min) 21 Channel Search – 22 S-Video In-Term (1) 23 Audio, Video In-Term (1) 24 Variable Audio Out (RCA Jack) 25 RGB Audio (L, R) 26 Mini D-Sub 15pin 27 Rod-Ant/Adapter –/–

MODEL No.

1 Picture Tube D/T Invar 2 Channel Capacity 181ch 3 C. Caption 4 MTS with dbx 5 Bass, Treble, Balance 6 Sub Audio Program 7 Remote hand unit Regu. 8 Nbr of RMT Button 29key 9 LED Indicators (P)

MM20E45

NEW

1-7

MM20E45 PC BOARD CONSTRUCTION

ITEM MM20E45 NEW MODEL CIRCUIT NOTE

DEF PB5227

POWER/VCD PB5226

249 x 330

POWER

dro

V/C/D

V-CUT LINE

Hole drawing: New

drop

Hole drawing: New

Def.

PB5227 (249.0 x 330.0)

Power/Audio

PB5226-1 (153.0 x 317.0)

Video/Chroma/Def

PB5226-2 (96.0 x 160.0)

Printed wiring board part code

P/P-M/P: 23534680B

Printed wiring board part code

P/P-M/P: 23534679B

SIGNAL/ VIDEO PB5228

249 x 330

SIGNAL

VIDEO

drop

D-SUB

Hole drawing: New

Signal

PB5228-1 (110.0 x 330.0)

Video (CRT/D)

PB5228-2 (119.0 x 210.0)

D-Sub

PB5228-3 (28.5 x 41.5)

Printed wiring board part code

P/P: 23534681B M/P: 23534681C

1-8

SECTION II CHANNEL SELECTION CIRCUIT

1. OUTLINE OF CHANNEL SELECTION SYSTEM

The channel selection circuit in the N5MM1 chassis employs a bus system which performs a central control by connecting a channel selection microcomputer to a control IC in each circuit block through control lines called a bus. In the bus system which controls each IC, the I2C-bus system (two line bus system) promoted by Philips Co., Ltd. in the Netherlands has been employed.

The ICs controlled by the I2C-bus control system are: ICG01 for audio system process, ICA02 for non-volatile memory, H001 for main U/V tuners, IC302 for deflection distortion corrections.

2. OPERATION OF THE CHANNEL SELECTION CIRCUIT

2-1 Channel Selection Control Microcomputer

(ICA01 Toshiba TMP87CM34N-3101)

8 bit microcomputer, TLCS-870 series for TV receivers, TMP87CM34N (42 pins, built-in CCD) developed by Toshiba is employed. With this microcomputer each IC and circuit shown below are controlled.

2-1-1 Non-volatile Memory IC

(ICA02 NEC µPD672CX)

(1) Memorizes data for video and audio signal adjustment

values, sound volume, woofer adjustment value, external input status, etc.

(2) Memorizes adjustment data for white balance (RGB cut

off, GB drive), sub-brightness, sub color, sub-tint, etc.

(3) Memorizes deflection distortion correction value data

adjusted for each unit.

2-1-2 U/V Tuner Unit

(H001 Toshiba EL911L)

(1) A desired station can be received by transferring a

channel selection frequency data (division data) to the I2C-bus type frequency synthesizer provided in the tuner and by setting a band switch data which selects the UHF or VHF band.

2-1-3 Deflection Distortion Correction IC

(IC302 Toshiba TA8859AP)

(1) Sets adjustment memory values for vertical amplitude,

linearity, horizontal amplitude, parabola, corner, pedestal distortion, etc.

2-1-4 Audio System Process IC

(ICG01, SONY CXA1784S)

2-1

3. SYSTEM BLOCK DIAGRAM

VIDEO SIGNAL PROCESS CIRCUIT

A/V DSP UNIT

25 24

QA01

TMP87CM34N-3101

B G

EXIT A

STB

CLK

DATA

AFT

SCL

SDA

DAC1

5 6

DAC2

PICTURE CONTROL

AUDIO CONTROL

TUNER/IF

MEMORY µPD6272CX QA02

KEY SWITCH

RGB MODE DISCRIMINATION

RELAY DRIVE

SYNC SEPA.

REMOTE CONTROLLER LIGHT ERCEPTION UNIT

KEY A

KEY B

15 MODE

RELAY

SYNC

RMT

OSC1

OSC0

RST

HOLD

VDD

VSS

DPG

MTS

H. PULSE

V. PULSE

6.13 MHz TRF1147T

8MHz CLOCK TCR1056

RESET CIRCUIT, 5V

GND

2-2

3-1 Microcomputer Terminal Name and Operation Logic

Terminal No. Terminal name I/O control resistor

1 RELAY Positive logic 2 P.B 3 4 MUTE Positive logic 5 STB T BUS PERIOD 6 CLK T BUS CLOCK 7 DATA T BUS DATA 8 I-CSTOP Negative logic

9 AFT 10 EXTA TV: H VIDEO/RGB: L 11 SPKOFF Negative logic 12 LINE21 13 KEY1 Local key input 0~5V 14 KEY2 Local key input 0~5V 15 MODE RGB MODE input 0~5V 16 17 Y IN 18 B IN 19 G IN 20 R IN 21 VSS GND 22 R 23 G 24 B 25 Y 26 HD H sync pulse input 27 VD V sync pulse input 28 OSC1 29 OSC0 30 TEST For microcomputer shipping test. Fixed low level 31 X IN 32 X OUT 33 RESET Negative logic 34 STOP Negative logic 35 RMT Remote controller signal det. Negative logic 36 SYNC Sync pulse signal input 37 SCL I2C BUS CLOCK 38 SDA I2C BUS DATA 39 TC1 GND 40 CSIN 41 VIN 42 VDD Microcomputer power supply

Oscillation connection terminal for OSD circuit

6.13MHz TRF1147T

High frequency oscillation connection terminal

Part for caption

2-3

3-2 DAC Terminal Name and Operation Logic

(1) DAC (QX01)

Terminal No. Terminal name Function I/O Logic

1 VDD INTERFACE POWER SUPPLY 2 DAT T-BUS DATA INPUT TERMINAL I 3 CLK T-BUS CLOCK INPUT TERMINAL I 4 PRD T-BUS PERIOD INPUT TERMINAL I 5 RESET 6 SUB-ADDRESS CHANGEOVER TERMINAL O 7 RGB CONT RGB CONTRAST O 0~5V 8 VSS GND 9 SBS SUB BASS SYSTEM O ON: L OFF: H

(H at SPK OFF) 10 RGB BRT RGB BRIGHTNESS O 0~5V 11 TNT TINT O 0~5V 12 COLOR COLOR O 0~5V 13 SHARP SHARPNESS O 0~5V 14 BRT BRIGHTNESS O 0~5V 15 CONT CONTRAST O 0~5V 16 VCC POWER SUPPLY

(2) DAC (QX001)

Terminal No. Terminal name Function I/O Logic

1 VDD INTERFACE POWER SUPPLY 2 DAT T-BUS DATA INPUT TERMINAL I 3 CLK T-BUS CLOCK INPUT TERMINAL I 4 PRD T-BUS PERIOD INPUT TERMINAL I 5 RESET 6 SUB-ADDRESS CHANGEOVER TERMINAL O 7 TV/RGB TV/RGB SWITCH TERMINAL O TV: L RGB: H

(L at RGB NO SIG.)

9 MUTE VIDEO MUTE O NEGATIVE LOGIC 10 H-POS H-POSITION O 0~5V 11 H-SIZ H-SIZE O 0~5V 12 V-POS V-POSITION O 0~5V 13 TV/RGB TV/RGB SWITCH TERMINAL O TV: H RGB: L 14 NO SIG NON/YES SIGNAL OUTPUT O YES: H NON: L 15 SUB CONT SUB CONTRAST (TV) O 0~5V 16 VCC POWER SUPPLY

2-4

3-3 Remote Control Code Assignment

Custom codes are 40H.

Key No.

Data code

Function

K1 00H 0 K2 01H 1 K3 02H 2 K4 03H 3 K5 04H 4 K6 05H 5 K7 06H 6 K8 07H 7 K9 08H 8 K10 09H 9 K11 0AH 100 K12 0BH K13 0CH RESET K14 0DH AUDIO K15 0EH PIC K16 0FH RGB/TV/VIDEO K17 10H MUTE K18 11H K19 12H POWER K20 13H MTS K21 14H OPTION K22 15H TIMER K23 16H SET UP K24 17H CH RTN K25 18H K26 19H CONTROL UP K27 1AH VOL UP K28 1BH CH UP K29 1CH RECALL K30 1DH CONTROL DN K31 1EH VOL DN K32 1FH CH DN K33 40H K34 41H K35 42H K36 43H K37 44H K38 45H K39 46H K40 47H K41 48H K42 49H K43 4AH K44 4BH K45 4CH K46 4DH K47 4EH K48 4FH

Continuity

Key No.

Data code

K49 50H K50 51H K51 52H K52 53H K53 54H K54 55H K55 56H K56 57H K57 58H EXIT K58 59H K59 5AH SET UP K60 5BH OPTION K61 5CH K62 5DH K63 5EH K64 5FH K88 97H K109 CCH K110 CDH K111 CEH K112 CFH

Function

Continuity

2-5

3-4 Local Key Assignment

1. Detection method of Local Key

Detection method of Local Key in N4ES chassis is analogue way to detect what voltage appears at local key input terminals (pins 13, 14) of Micom when the key is pressed. By this method, key detections of a maximum of 7 keys can be done, using local key input terminal (pin 13). As seen in the Local key circuit below, when one of key among S13-1 to S13-7 is pressed, the VIN which corresponds to the switch is applied to input terminal (pin 13). Judgement of key-input is done by measuring what voltage VIN is at the pin. Voltage measuring and key judgement are performed by A/D converter in Micom and by the software.

KEY No. Function

S13-1 POWER S13-2 CH UP S13-3 CH DN S13-4 VOL UP S13-5 VOL DN S13-6 ADV S13-7 MENU S14-1 RGB/TV/VIDEO

LOCAL KEY Assignment table

33K

7.5K

11K

16K

30K

68K

KEY1

33K

13 14

S13-1 S14-1

S13-2

S13-3

S13-4

S13-5

S13-6

S13-7

KEY2

2-6

4. I2C BUS INTERFACE OPERATION TIMING

As an example of I2C Bus interface operation timings, control for a memory IC will be shown below.

4-1 Write Mode (1 Byte)

Start bit issue

4-2 Read Mode

SDA

SCL

Start bit issue

15243

Slave address R/W command input

Slave address

Slave address R/W command input

R/W

6789

ACK signal output

R/W

5243

789

ACK signal output

ACK(OUT)

WA7WA6WA5WA4WA3WA2WA1WA

Word address input

ACK(OUT)

WA7WA6WA5WA4WA3WA2WA1WA

Word address input

Fig. 2-1

ININ

Start bit issue

ACK signal input

ACK(OUT)

D7D6D5D4D3D2D1D

ACK signal output

Word address update

Stop bit issue After completion of write operation word address becomes the write address +1 and held at that value.

R/W

ACK(OUT)

6789

15243

Slave address R/W command input

ACK signal out

INININ

Write data input

D7D6D5D4D3D2D1D

ACK signal output

OUT

Read data output

ACK signal input

ACK(OUT)

ACK(IN)

Stop bit issue

Fig. 2-1

2-7

4-2-1 Generation of Start/stop Status

SCL terminal

DA termianl

SCL terminal

SDA termianl

4-3 I2C Bus Data Format

(1) Memory IC * Write mode

Start

condition

152637489

D7 D6 D5 D4 D3 D2 D1 D0

Data transmission

Acknowledge

signal

Stop

condition

Fig. 2-3

Slave address 8 bits

A0H (WRITE)

* Read mode

Slave address 8 bits

(2) DPC IC

Slave address 8 bits

8CH

RW AC

Word address 8 bits

Sub-address 8 bits

Data 8 bits

Slave address 8 bits

Data 8 bits

AC ST

Data 8 bits

AC ST

2-8

(3) U/V tuner unit

Slave address 8 bits

RW AC AC ST

FM 8 bits

Main screen tuner: COH

FM: Variable divider control byte FL: Variable divider control byte CO: Charge pump sensitivity switching bit and test mode bit BA: Band switching bit

FL 8 bits

AC AC

CO 8 bits

BA 8 bits

2-9

5. SERVICE ADJUSTMENT MODE

1. Entering to Service Adjustment mode

Press MUTE key on the remote control unit once. Press again the MUTE key, and keep pressing it. Keep pressing the MUTE key, press MUTE key on TV set.

120H 8DH

Adjusting picture of NTSC mode

2. Switch-over of Service Adjustment mode

Every pressing of MENU key makes main address switch over.

161H 1E2H 120H 114H

Address

161H Video section sub-adjustment 1E2H OSD horizontal starting position 120H Deflection section sub-adjustment

Adjustment contents

120H 8DH RGB 350

Adjusting picture of RGB mode

4. Adjusting method of data

Pressing ADJUST UP/DOWN key on remote control unit changes the data value ranging from 00H to FFH.

5. Cancellation method of Service mode

The operation of key that accompanies display of other than from 1 to 4 makes the mode cancel.

During servicing in RGB mode, changing of the mode of RGB causes cancellation.

Address, Data Mode display of RGB

114H Multi-sound adjustment

3. Switch-over within Service Adjustment mode

Pressing of VOL UP key on remote control unit or on TV set makes address switch over cyclically, and VOL DN key switches over in reverse direction.

a) 161H 107H 163H 108H b) 1E2H c) 120H 121H 122H 123H 125H 126H

127H 128H 12AH 111H 112H

d) 114H 115H 116H 116H 117H 118H

119H

6. Other service function

MUTE key : Shipping-out preset RECALL key: Initializing of memory

2-10

ADDRESS OF SERVICE MODE

a) Video section sub-adjustment

Address

161H SUB BRIGHT 107H SUB COLOR 163H SUB TINT 108H SUB CONTRAST

c) Deflection section sub-adjustment

Address

120H PICTURE HEIGHT 121H V-LINEARITY 122H V-S CORRECTION 123H V-SHIFT 125H PICTURE WIDTH 126H E-W PARABOLA 127H E-W CORNER

Adjustment contents

b) OSD horizontal starting position

Address

1E2H OSD-H.POSI

d) Multi-sound adjustment

Address

114H ATT 115H STEREO VCO 116H SAPVCO (MSB) 116H SAPLPF (LSB) 117H FILTER 118H SPECTRAL 119H WIDEBAND

Adjustment contents

128H KEYSTONE 12AH V-CORRECTION 111H HORIZ POSITION 112H VERT POSITION

2-11

SECTION III RGB SIGNAL PROCESSING CIRCUIT

1. OUTLINE

The signal flow is explained as follows. RGB signal is input to D-SUB 15P and is processed to be output at CRT Drive circuit.

2. OPERATION AND FLOW OF RGB SIGNAL

Fig. 1 shows flow chart of RGB signal.

3. CIRCUIT OPERATION

(1) RGB signal input at D-SUB 15P is supplied to pins 2, 6,

10 of RGB signal processing IC M52327SP respectively.

(2) The signal which is input to RGB signal processing IC,

is processed in four steps ; 1) Amplification, 2) Contrast control, 3) Brightness control, 4) Black level clamp. After that, the signal is output at pins 28, 24, 20 and then is input to pins 1, 2, 3 of Signal switching IC AN5862K.

(3) In TV reception, R-Y, G-Y and B-Y outputs of IC501

TA8801AN are selected by IC216 AN5862K and ICR03 AN5862K, and are output at pins 5, 6, 8 of ICR03 AN5862K.

(4) TV/RGB switching pulse output from ICX001

TB1203AP, OSD switching pulse output from microcomputer and blanking pulse are input to OR gate circuit. And output from OR gate is input to pin 4 of ICR03 AN5862K. These operations function as following 3 items.

In TV mode, output from ICR03 AN5862K is turned over to TV. In RGB mode, OSD signal is made by OSD switching pulse from OR gate. In RGB mode, blanking is performed.

A8801AN

R-Y, G-Y, B-Y

utput

MICOM OSD output

MICOM Y output

(1)

RGB input

13 12 11

(3)

ICR02

RGB AMP

M52327SP

1) SIGNAL AMP

2) CONTRAST

3) BRIGHTNESS

4) CLAMP

321

IC216

SIGNAL

SWITCHING

AN5862K

ICX001

SWITCHING

SIGNAL

GENERATOR

TB1203AP

28 24 20

13 12 11

(2)

865

321

ICR03

SIGNAL

SWITCHING

AN5862K

(4)

OR GATE

865

Signal output

Blanking pulse

Fig. 1

3-1

SECTION IV CRT DRIVE CIRCUIT

1. OUTLINE

CRT Drive circuit is designed with its output load resistance decreased, to obtain wide frequency band, and heat-sink of output transistor is enlarged in size. Cut-off control and Drive control of TV signal are adjusted with variable resistors on CRT drive circuit, otherwise RGB signals are adjusted by bias control and gain control of RGB AMP ICR03 M52327SP.

2. CIRCUIT OPERATION

For example, Green axis circuit is explained as follows. (1) G signal which is output at pin 6 of AN5862K, is

supplied to the base of Q904, and is amplified in wide band by Q903 and Q904. Then it is input to cathode of CRT.

(2) The level of pin 7 of ICX001 TA1203AP becomes (L)

in RGB and (H) in TV. Utilizing this level change, emitter bias level of Q904 is changed over RGB mode and TV mode.

(3) The MUTE signal is generated at pin 9 of ICX001 in

POWER ON/OFF, CH selecting, MODE changing. This signal turns Q903 to cut-off to prevent disorder of picture from displayed on screen.

(4) Cut-off and Drive controls can be adjusted with R952

and R954.

+200V

+12V

RR25

DR08

RR26

L905

QR05

L904

R922, R923, R924

R925

R921

L906

R920

R926

ICX001 TA1203AP

TV/RGB Pin7

R209

Q206

+12V

R207

R941

ICR03 Pin6

R943

R942

Q907

ICX001 TA1203AP

MUTE Pin9

C909

C910

R944

R946

R964

R945

D904

Q908

RR24

CR13

R947

D905

Q904

Fig. 1

R961

DEF Circuit

R948

-Y

QR04

R927

R954

SERVICE SWITCH

R914

C904

R918

R949

Q903

C907

R915

Q904

D902

R918

R952

4-1

SECTION VMODE DISCRIMINATION CIRCUIT AND SYNC

SIGNAL PROCESSING CIRCUIT

Mode discriminating circuit performs to discriminate the kind of signals ; the signal which is input to D-SUB connector, is VGA, or is Macintosh signal.

Sync signal processing circuit performs to process sync signals into shape which can be utilized in horizontal and vertical osc circuits, because the signals which are input to D-SUB connector from a personal computer have various figures.

1.OUTLINE OF MODE DISCRIMINATING CIRCUIT

This model, for the simplification, reduces discriminating functions than CRT monitor for computer. The functions are those: to identify VGA signal or not; horizontal scanning frequency is higher or lower than 28kHz; the signal is input or not.

NO SIGNAL DISCRIMINATION ICH01, QH06

No signal

Hor. sync Vert. sync

POLARITY DISCRIMINATION ICH01

FREQUENCY DISCRIMINATION ICH04, ICH05

DECODER ICH02

VGA480 VGA400 VGA350

Low frequency

Fig. 1

VGA has three modes by number of vertical line. These are made to be able identify by polarity of horizontal and vertical sync signal. The difference of VGA mode signal is described in Table-1.

Kind No. of Ver. line fH fV Hor. Sync polarity Ver. Sync polarity

VGA480 480 31.5kHz 60Hz Negative Negative

VGA400 400 31.5kHz 70Hz Negative Positive

VGA350 350 31.5kHz 70Hz Positive Negative

Table-1

The above discriminated output is supplied to Ch. selection IC ICA01, and to be used as a sign to switch operations of related circuit.

5-1

2. OUTLINE OF SYNC SIGNAL PROCESSING CIRCUIT

As mentioned above, signal input at D-SUB connector from personal computer, sometimes shows various shape of sync signal. Representative signals are described in Table-2.

Kind Resolution fH Fv Hor. Sync polarity Ver. Sync polarity

IBM PGC 640 x 480 30.5kHz 60Hz Composite Sync

IBM VGA480 640 x 480 31.5kHz 60Hz Negative Negative

IBM VGA400 640 x 400 31.5kHz 70Hz Negative Positive

IBM VGA350 640 x 350 31.5kHz 70Hz Positive Negative

SVGA 800 x 600 35.2kHz 56Hz Positive Positive

Macintosh 13Ó 640 x 480 35.0kHz 67Hz Sync on Green or Composite Sync

VESA VGA 640 x 480 37.9kHz 72Hz Negative Negative

Table-2

Roughly classified, they are of two shapes; one is, like Macintosh, SYNC ON GREEN which is imposed on video signal, and the other is the output in TTL level separated from video signal. The TTL level method is classified to Composite Sync which combines horizontal and vertical sync, and to Separate Sync which separates respectively. And besides, in Separate Sync method, polarity is different by kind of signal.

Even though these various sync signal are input, always positive polarity of hor and ver sync signal is supplied to horizontal and vertical sync osc circuit. This is the role of this circuit.

5-2

3. MODE DISCRIMINATING CIRCUIT OPERATION

The circuit which discriminates three modes of VGA, is as follows.

DH31

19 18

ICH01

M52346SP

13 12 11 10

BCDA

ICH02

TC4028BP

fH > 28KHz/Hig

FREQUENCY DISCRIMINATION

Hor. sync Vert. sync

6 8 4 6 7

VGA350 VGA400 VGA480

Fig. 2

Mode discrimination of VGA is done by the circuit in Fig. 2. ICH01 M52346SP also performs process of sync signal, and the logic output is shown in Table-3. ICH02 is Decoder IC TC4028BP, and the truth table is shown in Table-4.

Input at pin 6

H. COMP.

H. COMP. (POS.) H. COMP. (POS.) H. COMP. (POS.)

H. COMP. (NEG.) H. COMP. (NEG.) H. COMP. (NEG.)

NON NON NON

Input at pin 8

NON V. (POS.) V. (NEG.)

Output pin

1 2 18 19

H H

L L L

L L H

Table-3. Logic output of M52346SP Table-4. Truth table of TC4028BP

When Macintosh signal is input in form of negative composite sync, diode DH31 prevents confusion between Macintosh signal and VGA400.

5-3

The outputs of VGA three modes are tabled as in Table-5.

ICH01 M52346SP ICH02 TC4028BP

Kind

pin 6 pin 8 pin 18 pin 19

pin 11

(D)

pin 12

(C)

pin 13

(B)

pin 10

(A)

output

(High)

VGA480 Nega Nega H H L H H H pin 4

VGA400 Nega Posi H L L H L H pin 6

VGA350 Posi Nega L H L H H L pin 7

Table-5

As shown in table above, since the result of frequency discrimination is input to pin 12 (c) of decoder ICH02, in case that frequency of input signal is lower than 28kHz, the mode is discriminated as not VGA mode even though polarity of sync signal is same combination as VGA.

Operation of frequency discriminating circuit is explained as follows, and configuration is shown in Fig. 3.

+12V

RH90

27K

RH64 33K

RH48

22K

CK24 M0.015

Hori. Sync

RH09

QH03 2SC752Y

DH03

1SS176

1SS133

12K

CH12

SL100P

RH10

QK11 2SC1815Y or 2SC17405,Q or 2SC1685Q

18K

CH14 M2.2

RH12 10K

RH13 10K

RH11 15K

RH14

10K

ICH04 IR9331

F/V CONVERTER

RH16

RH18

1/4W4.7KF

1/4W 82KF

F/V ADJ

H. OSC

Def. circuit

RH17 2KB

RH15

5.6K CH13

T1200

CH15 16V47

RH19

68K

RH21

1/4W11KF

RH75

8.2K

RH24 1/4W3.3KF

RH52

10K

3 RH26 1/4W1.8KF

RH20 1/4W 47KF

RH28 580K

+5V

DH04

1SS176

1SS133

RH23

1.8KG

ICH05

TA75902P

or LM2902N

RH27 680 QH10 2SC1815Y or 0

DH06 RD5.1ESAB1 or UZ5,1BSA

RH22 560KG

RK59

RK58 33KG

12KG

RH29 1/4W 13KF

RH30 1/4W

8.2KF

DK17 1SS176

1SS133

H.Size

CK17 M680

F/V

LOW FREQ

QH09 RN1202

Fig. 3

ICH04, F/V (Frequency-Voltage) converter, produces the voltage proportional to hor. scan frequency of input signal. This voltage is amplified in ope. amp ICH05. The comparator which is consisted of ICH05, compares frequency to operate so that emitter voltage of OH10 becomes HIGH level when the frequency is high.

5-4

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