Xoceco PH42T7 Schematic

PDP TELEVISION

PH42T7

CONTENTS

Safety Precautions………………………………………………………………………..…

Alignment instructions. ………………………………….…………………………….…

Method of software upgrading …………………………………………….……………………

Block diagram ……………………………..…..…..…..…..…..…….………….………….

Working principle analysis of the unit……………………..……………………….…………

Diagnose and service of panel……………………………………………………………..……

Wiring diagram……………………………………………………………………………..…

Assembly list………..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..…..….

Trouble shooting guide ………………………………………………………..……………... Ee

Exploded view...... …………………………………………………………………….…..

Part list........................................................................................................................30

Schematic diagram.....................................................................................................57

Note: This maintenance manual is intended only for the reference of the maintenance people. Please pay attention to the following points before carrying out the maintenance work.

Safety Precautions

Please read the “Points for attention for the Maintenance & Repair of PDP” and “Criterion for Identifying the Defects on Screen” as below, before inspecting and adjusting the TV set.

1. “Points for attention for the Maintenance & Repair of PDP”

To avoid possible danger, damage or jeopardy to health and to prevent PDP screen from new damage, the maintenance people must read the following carefully. If they ignore the following warnings, there will be deathful risks:

1.1 Screens vary from one model to another and therefore not interchangeable. Be sure to use the same type of screen in the replacement.

1.2 The operation voltage is approximately 350V for PDP module (including screen, driving circuit, logic circuit and power module). If you want to conduct maintenance work on PDP module when the set is in normal operation or just after the power is off, you must take proper measures to avoid electric shock and never have direct contact or touch with the circuitry of the working module or metal parts. That’s because within a short time relatively high voltage still remains on the capacitor of the driving part even after the power is off. Make sure to begin relevant maintenance operation at least one minute after the power is off.

1.3 Don’t apply on the module any power supply that is higher than the specification. If the power supply used deviates from the value given in the specification, there might be a possibility of leading to fire or damage to the module.

1.4 Never have operation or mounting work under unsuitable environment such as areas in the vicinity of water – bathroom, laundry, water chute of kitchen – sources of fire, heat-radiation parts or direct exposure to sunlight. Otherwise there will be kickbacks.

1.5 In case foreign substances such as water, liquid, metal slices or others fall into the module carelessly power must be cut off immediately. Keep the module as it is and do not move anything on the module. Otherwise it might be possible to contact the high voltage or cause shock short circuit so that it may lead to fire or electric shock.

1.6 If there is smoke, abnormal smell or sound from the module, please cut the power off immediately. Likewise in case the screen doesn’t work when the power is on or during the operation, please also cut off the power at once. No more operation in this case.

1.7 Do not remove or plug its connection wire when the module is in operation or right after the power is off. That’s because there remains a relatively high voltage on the capacitor of the driving circuit. If there is a need to remove or plug in the connection wire, please wait at least one minute after the power is off.

1.8 Considering the module has a glass faceplate, please avoid extrusion by external force lest it should cause glass breakage that may get people injured. Two people are needed in cooperation to move this module lest contingency takes place.

1.9 The complete TV set is designed on the basis of full consideration of thermal dissipation by convection, with the round hole on the top for heat emission. To avoid overheat, please do not have any covering on the hole during normal operation and never put it in the place where the space is narrow and in bad ventilation.

1.10 There is quite a number of circuits in PDP that are integrated ones. Please be on guard against

static electricity. During maintenance operation be sure to cover yourself with anti-static bag and before operation make sure to have it sufficiently grounded.

1.11 There are a big number of connection wires distributed around the screen. Please take care not to touch or scuff them during maintenance or removing the screen, because once they are damaged the screen will fail to work and it’s not possible to repair it.

1.12 Connector for the circuit board of the screen part is relatively fine and delicate. Please take care in the replacement operation lest it should get damaged.

1.13 Special care must be taken during transportation and handling because strenuous vibration could lead to screen glass breakage or damage on the driving circuitry. Be sure to use a strong outer case to pack it up before transportation or handling.

1.14 Please put it for storage in an environment in which the conditions are under control so as to prevent the temperature and humidity from exceeding the scope stipulated in the specification. For prolonged storage please cover it with anti-moisture bag and have them piled and stored in one place. The environmental conditions are tabulated as below:

Temperature Scope for operation 0~50centigrade

Scope for storage -15~60centigrade

Humidity Scope for operation 20%~80%

Scope for storage 20%~80%

1.15 If a fixed picture is displayed for a long time, difference in its brightness and color may occur compared with movable pictures. But it doesn’t show any problem and the reason is that there is reduced density of fluorescent powder in the former. On the other hand, even if changes take place in the picture, it can keep its brightness for a period of time (several minutes). It’s a feature inherent with plasma and it’s not abnormal. However please try as much as possible to avoid showing a still picture of high brightness for a long time during operation.

1.16 As a digitalized display devise, this module is provided with error diffusion technology and the gray scale and false enhancement of contour can be displayed by reusing of sub-field. As compared with cathode ray tube, it can be found in the moving picture that at the brim of the face of a person there are some wrong colors.

1.17 During the display of graph (indicating the gradual change in brightness horizontally or vertically) resulting from gray scale test it can be found that the brightness for the two adjacent levels is uneven. This is caused by the reuse of sub-field, the display of load rectification and the electrolysis.

1.18 The screen front plate is of glass. Please make sure that the screen has been put in place during erection. If it is not in place before the erection begins it may lead to screen crack or breakage.

1.19 Make sure the screw used in the mounting of the screen is of the original specs lest it should cause damage to the screen due to mismatch. Special care should be taken not to use too long or too big screw.

1.20 Care must be taken to guard against dust during assembling or dismantling, especially to avoid dirt from falling in between the screen and the glass lest it should harm the receiving and viewing effect.

1.21 There is piece of insulator stuck on the rear chassis corresponding to the power supply board. It is used to isolate the cool part from the hot part. Please take care to keep it intact lest it should

become a potential safety trouble.

1.22 In addition to plasma screen, the glass is a part of high value. It has such functions as anti-radiation, adjustment of color temperature etc. Please handle it carefully.

Alignment instructions

1 Alignment equipment

PM5518 (video signal generator) K-7253 (VGA signal generator) CA100 (white balancer) VG-849

2 Alignment flow-chart

The alignment flow-chart is shown as fig-1

Check MEGA8, DDC and FLASH

To produce digital board and HF board

Check the digital board and HF board

Connect with central signal source, then check each function of TV such as analog control etc., check the output of headphone and speaker

Input AV/S, HDMI and HD signal, then check each function of all the terminals

Input VGA signal (one format), check if the displ ay is normal under PC condition, check each function such as analog control etc. , check ho rizo ntal /vertical center etc.

Check the accessories and pack t hem in box

Fig-1 adjustment flow-chart

3 Unit adjustments

3.1 HF board adjustment Adjust the Potentiometer VR9002 on the power board, measure the test point TP1 (12VAMP) on the HF board to be 14 V±0.05 V.

3.2 Digital board adjustment

3.2.1 Connect digital board, button board and HF board, turn on the unit, check if display normal.

3.2.2 Enter factory menu mode (service mode) Press the MENU button, press the number button: 1 → 9 → 7 → 9, enter factory menu, then use VOL+/- select item value and CH+/- change it. Press the MENU button exit the factory menu.

All testing

Preset ex-factory

3.2.3 VGA channel adjustment

3.2.3.1 VGA channel mode preset Input VGA signal of K-7253, select 640*480/75Hz/85Hz, 1024*768/70Hz/75Hz/80/Hz/85Hz, 800*600/75Hz/85Hz, 1280*1024/60Hz/75Hz and 1600*1200/60Hz respectively, press “AUTO” to do the auto adjustment until the screen is filled with picture.

3.2.3.2 ADC adjustment of VGA channel Input the signal of 16 grades of grey density to VG-849 TIME921, PATTERN889, enter factory menu, select ADC auto correction.

3.2.3.3 White balance adjustment of VGA channel a. Input K-7253 8 level gray-scale signal of TIME303 (640*480/60Hz/) and PATTERN4718, enter white balance adjustment menu; adjust the third and seventh levels using white balancer. b. Select 9300k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 285 and 290 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 285 and 290. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 285 and 290. c. Select 12000k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 270 and 283 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 270 and 283. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 270 and 283. Note: after white balance adjustment, adjust 3.2.3.2 item, ADC auto correction again.

3.2.4 AV/TV channel adjustment

3.2.4.1 sub-brightness and sub-contrast adjustment Input the AV color bar signal (PM5518 COLOUR BAR 100%) to VIDEO terminal, adjust the sub-brightness and sub-contrast items of the factory menu, exit the factory menu and observe the effect, repeat the adjustment until it become best.

3.2.4.2 white balance adjustment of AV/TV channel a. Input AV signal (PM5518, 8 level gray-scale signal), enter white balance adjustment menu; adjust the third and seventh levels using white balancer. b. Select 9300k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 285 and 290 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 285 and 290. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 285 and 290. c. Select 12000k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 270 and 283 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 270 and 283. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 270 and 283.

3.2.5 White balance adjustment of YPbPr channel a. ADC adjustment of YPbPr channel: input the VG-849 TIME976 and PATTEN984 SMPTE Color Bar signal, enter factory menu, ADC auto correction. b. Connect YPbPr signal of K-7253 signal to YPbPr terminal, Input 8 level gray-scale of TIME380 (480i) PATTERN471 signal, enter white balance adjustment menu; Select 9300k of “mode”, fixed

offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 285 and 290 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 285 and 290. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 285 and 290. c. Select 12000k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 270 and 283 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 270 and 283. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 270 and 283. d. Input 8 level gray-scale signal of TIME392 (480p), TIME394 (720p) and TIME396 (1080i) mode, repeatedly it until the second color coordinate to 285 and 290 and brightness to 2.3nit.

3.2.6 white balance adjustment of HDMI channel Input VG-849 (1080i) and 720p HDMI signal, Select 9300k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 285 and 290 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 285 and 290. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 285 and 290. Select 12000k of “mode”, fixed offset_R to 128, adjust offset_G and offset_B, let the color coordinate of the third level be 270 and 283 and its brightness be 4.5-5nit. Fixed gain_B to 128, Adjust gain_R and gain_G, let the color coordinate of seventh level be 270 and 283. Adjust offset_G and offset_B and gain_R and gain_G repeatedly until the value of the two levels gray-scale to 270 and 283.

3.3 Performance check

3.3.1 TV function Enter searching menu → auto search, connect RF-TV terminal with central signal source and check if there are channels be skipped

3.3.2 AV/S, YPbPr and HDMI terminals Input AV/S, HD and HDMI signal, check if it is normal.

3.3.3 VGA terminal Connect to VGA terminal, input VGA format signal of 640 X 480@60 Hz, check if the display is normal. If the picture still interference, please auto adjustment the picture until it is normal.

3.3.4 DVI terminal Insert DVI terminal, input signal of 640 X 480@60 Hz signal and check if the display is normal.

3.3.5 Check sound channel Check the speaker and headphone of each channel.

3.3.6 presetting before ex-factory

Item Setting Item Setting Item Setting

Picture mode Sport OSD language English BALANCE +00

Sound mode NEWS VGA color

temperature

Warm Turn on

mode

Off

SCREEN Fill all

Method of software upgrading

Steps of software upgrading are as follows:

1. Select a serial connection wire and a VGA connection wire and then connect them by means of a patch panel;

2. Use a serial wire to connect the PC to the patch panel and set TV set to off state;

Open the software upgrade file holder and double click FlashUpgrader (window 2000/XP/NT)

The following interfaces will show up after running the program:

Based on the computer features, set up the serial port (COM Port). Select corresponding serial port (if it’s unable to FLASH WRITE, change to another port). Baud is selected to be 115200. Then select Reset Target After Download. Click FLASH pushbutton, it’s ready to run. For other settings, please refer to the Fig. Above (already defaulted by the system, normally no need to change). Switch on TV set the FLASH write program begins to run;

After FLASH write is over, push button “cancel” will become flash. Then shut the main power supply

and it’s OK just switch it on again.

Note: Do not shut the power off or turn the TV set on during the FLASH write. Otherwise it may lead to no way for flash to rewrite.

Block diagram

TUNER

AV1 Video AV2 Video

AV1 Audio

S-Video YPbPr1/YcbCr1 YPbPr2/YcbCr2 PC

HDMI

AudioRF

LA72700

or SIF

TV audioTV VIDEO

I2C

Audio

M51797

AV Switch

AV2 Audio HD2 Audio

Video

HDMI audio

PC audio

R2S15900

Audio switch and

control

SDRAM

PW2300

ADC+Decord

AD9398

HDMI

HD1 audio

I2C

24bit RGB

I2C

MP7720 x 2 Class D

JW1109

I2C

Flash MX29LV800

I2C

PW118

MCU and scaler

LVDS

Speaker

Earphone

PDP SCREEN

ATMEGA8L

power control

I2C

DDR SDRAM(128M) EM6A9320

Working principle analysis of the unit

1. TV board part

This set adopt all system for integrative tuner (include high frequency and intermediate frequency amplification circuit), the antenna receive the signal and send to the tuner, the tuner is controlled N602 PW118 MCU (by SDA, SCL), and select the appropriate channel, switch the right mode, after the high frequency amplification and intermediate frequency amplification, output the video and audio signals. The audio signal output by the tuner send directly to AV switch (M52797), select this signal and the audio signal from AV1, AV2, YPbPr, output the audio signal of the selected channel and separate to two ways; one way after amplifying 6 db is AU OUT; another way send to audio and sound processor IC N907 R2A15900. In R2S15900, such signal and audio signal of VGA, HDMI, YPbYr1 are selected by MCU, and output the signal by volume and treble-bass control into D type power amplifier to amplify, finally output to sound box and represent the sound. When insert the earphone, the jack of the earphone with the switch send the left/right track of the output of R2S15990 to the earphone power amplifier N908 NJW1109, after amplifying, when use the earphone output to the earphone jack to listen (the earphone can select by the customer’s request). The sound power amplifier MPS7720 is the high effective D type of power amplifier of the single track. The output power can reach 20W without radiating fin, provided with the protective function of overcurrent and overheat, when the direct-to-ground input is shorting, it can protect automatically and stop outputting. If it has been not shorting, it can resume normal circumstance. Therefore, when plug and play the audio cable (do not suggest such operation), if the set have no sound because of incautious shorting, it will get right as long as you restart it.

2.The picture part

The video signal outputted by the tuner send to AV switch M52797 (N903), input the video signal of AV1 and AV2 to M52797 (N903), and switch to gain two group of video output. One group output of video signal sends to the AV-OUT terminal with its sound output and treat them as the AV OUT output. Another group output of video signal send to PW2300 and make the video decoding, then the video signal of S-VIDEO, YpbPr1, YpbPr2, VGA send to PW2300 (N700) synchronously. All of these video signals shall be sent to this chip to make the video decoding or the AD conversion, and then output the 24bit digital RGB signal and the related sync signal. PW2300 (N700) complete mostly the function of 3D comb filter, the channel switch, 5 line Y/C separation, the colour decoding, and so on. 24 bit digital RGB signal and the related sync signal are outputted by PW2300 (N700) and are inputted to the next step chip PW118 (N602). The HDMI signal is inputted to AD9398 (N208) to make the decoding, at the same time 24 bit digital signal and the related sync signal are outputted and sent to PW118 (N602) to make the processing. PW118 is the new high-powered image manipulation chip of Pixelworks. The 24 bit digital RGB signal and the related sync signal outputted by AD9398 and PW2300 shall be inputted to this chip to make the image manipulation. In addition to the function of interlaced to line-by-line, this chip further include the function of image enhancement, etc.. PW118 can make the format switch for the different format inputted signal (under the customer’s request select SCALER function), and accord with the format request of the screen, and output the low-voltage difference signal of digital RGB LVDS, and then send to the screen and drive the screen. PW118 is the main CPU as well, the procedure store in external flash MX29LV800 N404. The software update of RS-232 is that update the stored content of the N404 by

PW118.

3. IC function, the internal block di agram, t he pi n introduction

3.1 PW2300 PW2300 is a piece of the front-end video-processing chip that integrates a high-powered, multi-system video decoder with a high speech ADC module. All of the input video signal (except for HDMI signal) are inputted to this chip to the AD switch and video decoding, 24 bit digital RGB signal and the related sync signal are outputted to N602 PW118 to make the processing. PW2300 complete mainly the functions of 3D comb filter, the channel switch, 5-line Y/C separation, the color decoding and so on. It connect external SDRAM chip N703 HY57V161610E treated as the internal memory to assist the operation of PW2300. PW2300 internal block diagram:

PW2300 the arrangement diagram of the pins:

PW2300 instruction of the pin:

Pin Name Function Pin Name Function

A4 XIN Resonator input N4 B_1 AV1 blue input

A5 XOUT Resonator output P1 R_2 AV2 red input

B2 SDA I2C bus data P2 B_2 AV2 green input

B3 SCL I2C bus clock R3 CVBS_SOG1 T multiple green sync output

of video signal

K2 VGA-R1 VGA red R4 C_1 S-VHS color signal input

K1 VGA-G1 VGA green B9 GVBI Vertical blanking interval

M1 VGA-B1 VGA blue E16 G_VS Vertical sync output

T1 VGA_H VGA CH1 horizontal

sync

T3 VGA_V VGA CH1 vertical sync F15 G_AHS Crude horizontal sync

N1 R_1 AV1 red input G15 G_DLK Clock output

N1 G_1 AV1 green input B10-B12

P3 SOG_2 AV2 green sync input C13,

P4 G_2 AV2 blue input B15-B16

F14 G_HS Horizontal sync output

GRE (0-7) Red data output

A10-A12

C11-C12

GGE (0-7) Green data output

C14

B13,

B14

A13-A16

Blue data output

C15-C16

E14

GBE (0-7)

3.2 AD9398 The chip of high-definition multimedia interface, AD9398 HDMI (High-D efinition Multimedia Interface) this interface is the digital interface standard that bring up rapidly. The use of this interface is the transmission of electronic video signal of standard definition and high definition, and this interface provide the content protect technology. AD9398 also support HDCP (High bandwidth Digital Content Protection). AD9398 include a HDMI 1.0 interface module and a HDCP module. The inputted HDMI signal will be sent to the interface of this chip to make the decoding, simultaneity 24-bit digital RGB signal and the related sync signals are outputted to N602 PW118 to make the processing. Moreover, HDCP module makes the communication by DDCSDA, DDCSCL and HDMI signal sources to make the video signal decoding. The chip connect a external memory N207 24LC168SN that store the secret key of decoding required by HDCP, and make the communication by the pin MCL, MDA of AD9893.

AD9880 (AD9398) internal block diagram:

AD9880 (AD9398) instruction of the pin:

Pin Name Function Pin Name Function

2-9 GGE(0-7) Switch output 44 RXC+ DVI digital video input

12-19 GBE(0-7) Switch output 49 DDC_CLK HDCP (serial data clock)

92-99 GRE(0-7) Switch output 50 DDC_DATA HDCP (serial data I/O)

20, 21 MCLK Control clock output 51 MCL HDCP control series data

clock

22 I2S_SCK Audio series clock output 52 MDA HDCP control series data

I/O

23 I2S_WS Bus clock data output 82 SCL-1 Series data clock

27 I2S_SD Bus audio data output 83 SDA_1 Series data I/O

34 RX0- DVI digital video input 84 G_FIEL0 Parity field output

35 RX0+ DVI digital video input 85 G_VS Vertical data sync output

37 RX1- DVI digital video input 86 G_VHS Green sync output

The arrangement diagram of the pins:

3.3 PW118 PW118 is the new high-powered image manipulation chip of Pixelworks. The 24 bit digital RGB signal and the related sync signal outputted by AD9398 and PW2300 shall be inputted to this chip to make the image manipulation, and are outputted LVDS signal to drive the screen directly. In addition to the function of interlaced to line-by-line, this chip further include the function of image enhancement, etc. This chip is the main CPU of this set. It take charge of all control except for the power supply control, including the control of each chip operation in the main board (eg. the image manipulation, the channel switch, the image display, etc.), the control of the button, remote device and sound, etc., and the assistant CPU N401 ATMEGA8L control mainly the power supply, including the stand-by and the control button of remote device to turn on the set, etc. The menu interface also generate by PW118. The external memory of PW118 N402 AT24LC32A stores the related data. The Flash chip N404 MX29LV800 store the related procedure, the chip DDRSDRAM (N501 K4D553238F-JC) assists the operation of PW118 as the external memory.

PW118 internal block diagram:

The arrangement diagram of the pins:

3.4 M52797 M52797 is a AV switch chip controlled by IIC. This chip include 4 group of video input and 4 group of audio input, 2 video output and 1 audio output.

M52797 Internal block diagram:

The arrangement diagram of the pins:

M52797 instruction of the pin:

Pin Function Pin Function

3 YPbPr2_L audio input 20 Video output to PW2300

5 YPbPr2_R audio input 22 Right track audio output

6 AV1_L audio input 23 Video output to AVOUT interface

7 AV1 audio input 24 Left track audio output

8 AV1_R audio input 25 TV_R audio input

9 AV2_L audio input 26 TV video input

10 AV2 audio input 27 TV_L audio input

11 AV2_R audio input

3.5 R2S15900 R2S15900 is a audio processing chip that take charge of audio switch, sound processing and volume adjustment, controlled by IIC bus. Internal block diagram:

R2S15900 instruction of the pin:

Pin Function Pin Function

2, 27 Left and right track of M52797 5, 24 Left and right track of YPbPr1

3, 26 Left and right track of HDMI 11, 19 Left and right track of audio output

4, 25 Left and right track of VGA

3.6 LA72700 (STEREO/SAP DECO DER) :

PIN description:

Pin No. Name Description Pin No. Name Description

5 PISIF Audio IF input 25 R OUT Right channel audio output

11 SDA I2C bus 26 LOUT Left channel audio output

12 SCL I2C clock 31 VCC 9V

Diagnose and service of panel

1. Block function of panel The power supply board, Logic board, X drive board, Y drives board, Logic BUFFER (E, F and G) and Y BUFFER (upper and lower) of the PDP panel.

Y BUFFER (upper)

Y BUFFER (lower)

Logic BUFFER (E)

Logic BUFFER(F) Logic BUFFER(G)

Power supply board

X drive board Y drive board

Logic board

COF(7 piece)

* Power supply board: to supply power for the screen, other functional modules on the screen, our

own main board, and video frequency processing board.

* X driving board: to produce and provide driving signal for X electrode according to the time

sequence signal sent from logic board.

* Y driving board: to produce and provide driving signal for Y electrode according to the time

sequence signal sent from logic board.

*Logic board: to process the image signal sent from the main board, to produce addressing signal and to provide driving signal for X and Y driving boards. *Logic BUFFER board: To convert the data signal and control signal sent from the logic board into the signals required by COF. *Y BUFFER board: to transmit the scanning signal from the Y driving board to the screen, which is

divided into upper and lower parts.

*COF: to convert the signal sent from the logic BUFFER board into the address signal used by the screen.

2.Trouble diagnosis:

2.1 The screen is not bright: a. Check if the power supply plug from the power filters board to the power supply board is well

inserted into the socket. If not, plug it in.

b. Check if the fuse on the power supply board is blown up. If yes, replace it for a good one. c. Remove our main board and the video frequency processing board, ground the pin 4

POWER_ON/OFF of socket CN802 of the power supply board;

SW200

Solder point

and then push the slide switch SW2001 on the logic board to the internal modes (1, 3 up and 2, 4

down) from external modes (1, 2, 4 up and 3down).

Switch the power on and see if the screen is lit. If the screen can give a normal and completely white field signal, then the problem lies in our main board or video frequency processing board, which will be dealt with separately. d. If the screen is not lit, then first replace the power supply board to see if the problem is solved. e. If the problem remains after the power supply board is replaced, then the problem lies in the screen, replace the entire screen for treatment.

2.2 There appears on the screen a line or several unlit lines.

Check if the socket between Y driving board and Y BUFFER is plugged well. If not, plug it well. If

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