When i power on the laptop the screen appereswhite..i change lcd , cable , and inverter.but tbe problem presest.give me a solution for this problem

1) Wrong LCD screen

2) Video Cable (LCD Cable) is not connected tightly.
Motherboard side, or LCD screen side; or both.

3) IF, a screen Inverter is used, the small cable from the Video Cable, that connects to the screen Inverter; is not connected, or has a loose connection to it. (screen Inverter)

4) An LCD screen, and a screen Inverter are a Matched unit.
If it's the wrong LCD screen......................?

5) IF, a screen Inverter is used; the diagnosis was wrong, and the LCD screen was replaced.
90 PERCENT of the time, the fault is a bad screen Inverter.

A) Laptop's LCD screen uses a CCFL, (Or more than one), for a Backlight; the laptop uses a screen Inverter.

Diagnostic flowchart leads from Graphics Chipset, to Video Cable, to screen Inverter, THEN, LCD screen.
Expensive LCD screen was replaced, instead of the actual part that needed replacing;
Video Cable: $9 to $22
Screen Inverter: $9 to $22

LCD screen: $60 to $245

B) Laptop's LCD screen uses LED backlighting, and does NOT use a screen Inverter:

Diagnostic flowchart is;
A) Video Cable;
A Video Cable should have it's connections PHYSICALLY checked.
You have to try to push the connectors in tighter.
Visual inspection alone will NOT do.

Making sure the Video Cable connections are tight, and this does not fix the problem, then the Video Cable needs to be removed; and every wire in the Video Cable checked for Continuity with a multimeter set to OHM's. (1K)

Not feasible, then take the Video Cable down to the nearest small computer shop; and have the resident tech check it for Continuity.
Should only be a few bucks.

Or just replace the Video Cable.
(Parts changing I know, but...........?)

Primer:
An LCD screen cannot produce light. It needs an additional light source.
A Backlight is the additional light source.

A Backlight can be a CCFL, (Or more than one), or a series of LED's.
(Light Emitting Diode)

A CCFL is a Cold Cathode Fluorescent Lamp. (Bulb)
Similar to Fluorescent lighting used in homes, and businesses; but on a MUCH smaller scale.

Average thickness is 2mm. That is a little large than 1/16th of an Inch.
Average thickness is almost as long, as the LCD screen is in height.
View the last 8 photos,

http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/

A screen Inverter is used to convert the power, (Electricity), from the laptop; for the LCD screen, and Backlight.

As previously stated, Backlighting that uses CCFL, uses a screen Inverter.
LED backlighting MAY, or MAY NOT use a screen Inverter.
When the LED backlight technology first came out, it seems some did use a screen Inverter.
It also seems as the technology advanced, LED backlighting does Not use a screen Inverter.

Regards,
joecoolvette

1) Take a flashlight and shine at the LCD screen at various angles. See if there are faint images.
If faint images are seen the problem most likely will be the Inverter.

An LCD screen cannot produce enough light by itself. There needs to be an additional light source.
The additional light source is a Backlight.

A Backlight is a CCFL
Cold Cathode Fluorescent Lamp
Similar to Fluorescent lighting used in homes, and businesses, but on a Much smaller scale.

(A typical Backlight is varies in length, and is usually half the diameter of a No.2 pencil.
Example of a typical Backlight,

http://www.buy.com/prod/new-15-inch-ccfl-backlight-for-toshiba-satellite-a55-s106/q/sellerid/23962916/loc/101/212931234.html

In the example given there are 9 Backlights shown. Click on the Backlight images to enlarge)


An Inverter is used to change the power from the laptop, and provide power to the LCD screen, and Backlight.

90 Percent of the time the Inverter is bad.

An Inverter is a small circuit board, and is located behind the Bezel, and usually at the bottom of the LCD screen.
(The thin plastic 'frame' going around the front of the LCD screen, is the Bezel)

If faint images are seen with the flashlight, replace the Inverter.

If you post the laptop's manufacturers name, and Model Number in a Comment, I may be able to give you a link to a free Service Manual detailing how simple it is to replace an Inverter.

I could also give links to possible choices for an Inverter.
(The Model Number is on the bottom of the laptop)


2) If no faint images are seen there is a problem with the graphics.
This could be due to something as simple as a Display Video Cable, or the graphics chipset itself.
(Not so simple)

The Display Video Cable comes from out of the body of the laptop, and usually runs next to one of the hinges. It then leads up into the Display Assembly, and attaches to the back of the LCD screen.

Constant opening and closing of the laptop may have damaged the cable, or could have sightly unplugged it.
The first thing to try would be to see if the cable's connector has come loose.
The next thing would be to check the continuity of the cable, and if damaged replace the cable.

(The continuity of the cable can be checked with a multimeter set to OHM's. An economical multimeter can be purchased for as little as $10 to $12)


There is also a Display power cable that goes to the Inverter. With some laptop models it is incorporated into the Display Cable. This cable can be damaged by opening, and closing the laptop repeatedly, or become loosened, and slightly unplugged.

(Some laptops are designed where this is never a problem. Other laptops are designed where this can be a frequent problem. Poor engineering design)


2A) There are some laptops, specifically the HP Pavilion dv2000 series, dv6000 series, and dv9000 series that have a problem with the graphics chipset is overheated.
Poor cooling design inside the laptop.

This explains more about it,

http://www.youtube.com/watch?v=bnkQNmKauEc

For questions please post in a Comment.

Regards,
joecoolvette

You might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp.

In this service manual, you will find an illustration of how to disassemble the laptop & replace either the LCD cable or screen inverter board:
http://h10032.www1.hp.com/ctg/Manual/c01295820.pdf

Try attaching an external monitor to the laptop & see if you could get any display on it. If this is successful, then you might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp

Try attaching an external monitor to the laptop & see if you could get any display on it. If this is successful, then you might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp

Try attaching an external monitor to the laptop & see if you could get any display on it. If this is successful, then you might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp.

Try attaching an external monitor to the laptop & see if you could get any display on it. If this is successful, then you might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp.

You can determine if the bulb is bad by simply connect a monitor to the fifteen pin AGP port located at the side of your computer usually color blue. If your computer display the desktop on the monitor,you should change the bulb in your computer display.To change the backlight you need to follow these steps :Power off your Toshiba laptop and make sure the AC adapter is unplugged.
Remove the screws on the side of your laptop screen. Once the screws are removed, you can remove the plastic bezel (screen guard).
Pop the bezel out, exposing all of the LCD screen. Pull the LCD screen gently away from the computer by the corner. Be mindful that the screen is still connected to the computer by a ribbon cable.
Remove the tape over the ribbon cable where it connects to the screen, and gently pull the cable to disconnect it.
Turn the LCD face down, and remove the piece of tape that holds the top metallic foil against the back of the LCD.
Lift the metallic foil to expose the backlight. Remove the single screw at the end of it that holds it in place. Unclip the wire at the end of the backlight from the inverter (power source to the backlight), and remove it from the LCD. Replace it with the new backlight (available at any electronics store or online), and reassemble the device the same way you took it apart.

This might be a sign of a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp.

Test with an external monitor attached to the laptop. If you get display on the external monitor, then this confirms the case

Sounds like either your backlight bulb has failed or the inverter that powers the bulb has failed or a connection has come loose from the inverter to the LCD panel. Unless the laptop was "Jarred" or dropped, I doubt the bulb has burned out....most likely if no damage occued, the inverter has failed or there is a loose connection with the inverter.