PLASMA TV – FAULTS – CIRCUIT BOARD FUNCTION DETAILS - TROUBLESHOOTING
PDP circuit boards
VIF Board
General digital video signals include Vsync, Hsync, R(8Bit), G(8Bit), B(8Bit) and Data Enable (Blank);the VIF of PDP is making for processing these digital signal. Because PDP belonging a high end product, so its application should include the functions of Monitor (analogue VGA, digital DVI signal input). And for consumer’s sake, the VIF should have the functions of video, like audio, composite, s-video, component signal processing.
General digital video signals include Vsync, Hsync, R(8Bit), G(8Bit), B(8Bit) and Data Enable (Blank);the VIF of PDP is making for processing these digital signal. Because PDP belonging a high end product, so its application should include the functions of Monitor (analogue VGA, digital DVI signal input). And for consumer’s sake, the VIF should have the functions of video, like audio, composite, s-video, component signal processing.
Currently the video signal sources are video cassette recorder,
DVD player, CATV, RF tuner, VGA card (PC). In order that all the video signal
sources can be displayed on PDP, so we need an interface to transfer these
signals to a specified signals for PDP to display and this is the function of
VIF (Video Interface).
Basic framework of VIF board
For dealing with the
signals of CVBS, S-video and Component, it requires a video decoder IC. And the
output of video decoder will input to a de-interlace chip IC for a stable image
quality. Because the TV system uses interlace scanning, it causes flickers on
the screen. To improve this situation so we use a de-interlace chip IC. The ADC
(Analog to Digital Converter) IC converts the analogue RGB signal to digital RGB
signal. The TMDS (Transition Minimized Differential Signalling) decoder IC
transmits digital RGB signal. All the output of ICs’ signal sends to scalar IC.
1. ADC Converter: AD9888
The AD9888 is a complete 8 bit, 205 MSPS monolithic analogue interface optimized
for capturing RGB graphics signals. Its 205 MSPS encode rate capability and
full-power analogue bandwidth of 500 MHz supports resolutions up to UXGA (1600
x1200 @ 75 Hz).
2. TMDS Receiver: SIL153BCT100
The Sil153BCT100 receiver uses Panel Link Digital technology to support high
resolution displays up to SXGA (25MHz~112MHz). The Sil153B receiver supports up
to true color panels (24 bit/pixel, 16.7M colors) in 1 or 2 pixels/clock mode.
In addition, the receiver data output is time staggered to reduce ground bounce
that affects EMI.
3. VIDEO Decoder: SAA7118E
The SAA7118E decoder is a ADC too, but it can deal with the ordinary TV
signals. The SAA7118E can input Composite, S-video, Component and its outputs
are digital Y(Luminance) , C (Chromacity) signals. And also can adjust
brightness, contrast, saturation, hue.
4. De-interlace: The Sil504 transfer interlacing signals to progressive signals. The advantage
of progressive signals is that the scanning rate doubling to let the screen
more stable and non-flickering. Besides, the sources of input may have 24 0r 30
or 25 frames per sec, so the de-interlaced chip shall tell from the differences
and processing the signals. The basic principle of de-interlaced IC is combined
the odd and even fields to a frame, and the processing needs a memory IC (SDRAM)
to stock these signals for processing. For the improving the quality of image
sake, more and more TVs or DVD players all have the functions of progressive
scanning.
5. Image Processor chip:
PW171-20U (system on chip).
Scaling function
The Image scalars provide
high quality up and down image scaling. For the applications of VIF, the input
signals could be VGA, SVGA, XGA formats, and its output fixed at 852 x 480 @60
HZ. For example, SVGA format: 800 x 600 @75Hz, first scaling down: Horizontal
800 640 Vertical 600 480, 75 frames / sec after frame rate conversion become 60
frames per sec. Then scaling up 640 852, to accomplish the scaling function.
Micro Processor Function
This chip includes
microprocessor (on-chip 80x86); selectable function and I/O interface control.
With 3 groups of 8-bit programmable I/O, 1 group of RS-232 communication port,
IR decoder, timer and a PWM generator ◎ OSD Function: The
on-screen-display (OSD) can be used for startup screens, menus, and scribble
functions.
VIF (Video interface)
d-1. When main switch is ON, the power board generates Vsby 5
volts to VIF board. The IC of microprocessor becomes standby status waiting for
a startup signal from key-pad or receiver.
d-2 When a startup signal is detected then microprocessor sending
a ON signal to the power board through CN connector , and the power board
begins generating all voltage to PCB board(Vs, Vxg, Vw, Vf, Vdd, Vcc, 9volts) .
At the same time VIF will generate background light and OSD menu as select.
After searching a input source, then will display on the PDP screen, if there
are audio signals , it will amplify and send to speakers through audio board.
d-3 If there are abnormal signals are detected(such as over
voltage , over current , low voltage ..) , the power board will send abnormal
detective signal to shut down all the system.
DIF Board
Function: The video or pc
signal is processed and send to DIF form VIF. There are gamma correction, basic
white balance data, power loss control, and data translation function. When DIF
board work normally the LED on the board should light. When you turn on the
main power switch this LED should light a few seconds to inspect itself and
then disappear.
X/Y Sustainer Board
Receive the signal from DIF.And output high voltage scan signal to panel.
Audio Amplifier Board
It comprises special switch mode power supply and audio amplifier and electronic switch for outer and inner speakers exchange. It connects to 300V from main power supply on the module from socket CN5601. M5502 connects to inner speakers by cable. M5503 connects to outer speakers socket boards by cable. M5501 connects to VIF and receives the R,L audio signal, MUTE, SWITCH control signal. The inner output power is up to 4W, And the outer output power is up to 20w together on 4ohm impedance.
Receive the signal from DIF.And output high voltage scan signal to panel.
Audio Amplifier Board
It comprises special switch mode power supply and audio amplifier and electronic switch for outer and inner speakers exchange. It connects to 300V from main power supply on the module from socket CN5601. M5502 connects to inner speakers by cable. M5503 connects to outer speakers socket boards by cable. M5501 connects to VIF and receives the R,L audio signal, MUTE, SWITCH control signal. The inner output power is up to 4W, And the outer output power is up to 20w together on 4ohm impedance.
Abnormal Phenomena
VIF board
a. color absence or colour step not good.
b. No sound from the speakers, but there was noise output.
c. Power supply is normal; there were OSD and background light on
the panel, but not picture.
d. Cannot turn on the set (LEDs do not work).
e. There is some strip disturbance in the picture.
f. Turn off automatically after the set works a few minutes. g.
Picture wobbles when input 1080i signal.
DIF board
a. picture abnormal.
b. Cannot turn on the set (LEDs do not work).
Power Supply
a. no picture output.
b. Output voltage abnormal.
X Scan sustainer
h. no picture.
i. Colour of the picture is not enough.
j. Picture abnormal such as picture flicker
k. Cannot turn on the set (LEDs do not work)
Y Bulk Sustainer
a. Cannot turn on the set.
If disconnect the cable from power supply to Y sustainer the set works, but the
picture is dark. It means that Y sustainer is abnormal.
b. Power output voltage is normal, but the picture is dark.
c. When the set works normally, the temperature of the components
on the sustainer boards is about 55. If the temperature is over 55 ℃ there may be some fault on
there.
Audio Amplifier Board
a. there is no sound or noise in the speakers.
b. Too much noise in the speakers.
c. Cannot switch inner and outer speakers.
X Connecting Board (upper and lower parts)
Y Connecting Board (upper and lower parts)
Short Repair procedure
1. No picture and Red LED does not light, make sure the main power
switch on and to check the fuses on the power supply board and power filtering
board.
2. Turn on the main power
switch, the green LED lights. But there was no picture. Check VIF or DIF or X
sustainer or Y sustainer. You may exchange them one by one with good boards.
Replace VIF, and then turn on the switch, remote the set. If there are OSD,
there is some fault in the VIF.
3. If the picture is vague,
please replace the Y-sustainer board.
4. The picture is separated into upper & lower parts, one part
has picture, the other has no, and the picture is from left to right, please
check the X connecter board and the X-sustainer board.
5. If the picture is vague or the picture of the upper or the lower
part is dark, please check the Y connector board and the Y-sustainer board.
6. Check whether the corresponding W board and the connect cords
are in good condition; otherwise, the module is iffy.
Dark vertical bar or strap.
7 Check whether the left (sight from the rear) Y connector board
and the connect cords are in good condition; otherwise, the module is iffy.
8 If the chroma of the
white signal isn’t uniform, adjust the Vs, VXG voltage according to the
voltage data of the PDP module.
9 If many details of the picture are short of, or the pixels of
the picture are not discontinuous, the Pixel works IC doesn’t weld well, please
replace the PC1 board.
10 Trouble of the DIF and the W connect cords or the connect jack.
There are many dark flicking bright dot defect or a single or
multi pieces of line always appear in the screen:
Replace the PDP module.
