Jeff, connect an external monitor for a diagnostic test.
Laptop OFF, monitor OFF, connect a VGA monitor to the VGA port on the back of the laptop,
(RGB/Monitor connector,
http://en.wikipedia.org/wiki/VGA_connector )
The external/VGA monitor can be a CRT type (Looks like a small TV), or a flat LCD screen that has a VGA cable.
Turn the external monitor on. If a CRT type allow it to warm up.
Turn the laptop on.
By default the display should show on the external monitor. If not press, and hold down on the Fn key, and tap the F5 key. (One of the Hot Key's)
If the display still does not show, hold down on the Fn key, and tap the F5 key again.
There are three display options;
1) Internal monitor of laptop ONLY
2) Internal monitor of laptop AND external monitor
3) External monitor ONLY
If graphics show on the external monitor, you have a problem in the Display Assembly, and/or the Video Cable.
If graphics do Not show on the external monitor, you have a problem with the graphics chipset on the motherboard.
(ATI Radeon 3100)
http://www.irisvista.com/tech/laptops/Toshiba-Satellite-Pro-L450-L455/laptop-disassembly-1.htm
Video Cable
1) Could be the connections. The connection of the video cable TO the motherboard, and the other end of the video cable TO the back of the LCD screen. (In the Display Assembly)
2) Could be damage to the video cable. Check the sheath of the cable for obvious signs of damage. If so, the thin tiny wires inside may be damaged also.
Cable should be checked for continuity of each wire in the cable. (Ohm's with a multimeter)
Video Cable condition, and tightness of connections check out, it's on to the screen Inverter.
Primer:
An LCD screen does not produce light by itself. It needs an additional light source.
A Backlight is the additional light source.
A Backlight is a CCFL, or a series of LED lights.
The Toshiba Satellite L455D-S5976 Notebook PC, uses 1 single CCFL for a Backlight.
Cold Cathode Fluorescent Lamp.
Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.
A screen Inverter is used to convert the power (Electricity) from the laptop, for the LCD screen, and Backlight.
90 PERCENT OF THE TIME the fault is the Inverter.
The screen Inverter is a small rectangular circuit board, and is located behind the Display Bezel, an at the bottom of the LCD screen,
Example of screen Inverter,
http://www.battery-stores.co.uk/laptop-inverter.php/toshiba_Satellite+L455D-S5976_205_5226.htm
Link to a free Service Manual for the Toshiba Satellite L455D series of Notebook PC's,
http://www.tim.id.au/blog/tims-laptop-service-manuals/#toc-toshibaUnder the main Toshiba heading go down to the subheading -
Satellite A10. (A10 is in blue)
In this 'paragraph' go down to the third line, and scroll across to -
L450D, in blue.
Click on L450D.
This is a PDF file. The computer you are using now has Adobe Reader on it, which uses PDF files.
After you click on the file name { L450D } it may take up to 30 seconds before the first page comes up.
Would appreciate it if you would post back in a Comment with your findings.
Regards,
joecoolvette
On a Toshiba A75 S206 which key is used with the FN to use an external monitor. It isn't F4.
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