"Power passes through the laptop but the monitor is black"
I'll assume you mean the Indicator LED lights come on, and the Harddrive Activity LED light flashes.
[Not that you have tested the Voltage going to the Inverter, or Voltage coming out of the Inverter to the LCD screen]
1) Suggest you first test to see if the problem is the Inverter, or the graphics chipset on the motherboard.
Attach a VGA monitor to the VGA connector on the back of the laptop. (Laptop and monitor off)
http://en.wikipedia.org/wiki/VGA_connector
Turn the VGA monitor on, allow it to 'Come to life'.
Turn the laptop on.
Press and hold down on the Fn key, then tap once on the F key that toggles the display over to an external monitor.
(Generally the F5 key. The display toggle key may have two symbols on it.
One is an icon of a laptop that is open, then there is a slash /, and an icon of a Monitor. (Rectangular outline)
Since you did not post the Model Name, and Model Number, I can only give you generic information)
No display? Tap the display toggle key again.
Display?
Chances are that you just have a bad Inverter.
An LCD screen cannot produce enough light by itself. It requires an additional light source.
A Backlight is the additional light source.
A Backlight is a CCFL.
Cold Cathode Fluorescent Lamp
Similar to Fluorescent lighting used in homes and businesses, but on a Much smaller scale in size.
[Typical example of a Backlight,
http://www.buy.com/prod/ccfl-backlight-lamp-toshiba-satellite-1805-s204-13-3-wxga/q/sellerid/23962916/loc/101/215969147.html ]
An Inverter is used to provide power to the LCD screen, and the Backlight.
An Inverter is small circuit board. Typically 3 to 5 inches long, and the width of a finger.
An Inverter is typically located behind the Display Bezel, and at the bottom of the LCD screen.
Attached with a screw, two screws, or tape.
90 PERCENT of the time the fault is the Inverter.
[Typical example of an Inverter,
http://www.laptopbattery-usa.com/toshiba-satellite-p20-p25-p30-p35-laptop-lcd-inverter-p-1959.html?zenid=refnsit173e8eti5lg1ffp8sh0
2) IF the display does Not come on the external monitor.
Some models of laptops have a poor cooling system design for their GPU chipsets.
(Graphics Processing Unit. or slang term > graphics chipset)
The cooling system varies from laptop manufacturer to laptop manufacturer, and model to model, but typically;
A) Cooling Fan
B) Heatsink
C) Cooling Tube
Typical construction of a Heatsink is a plate of metal with tall, thin fins protruding from it.
The tall, thin fins absorb heat from the plate of metal.
The fins then radiate the heat away.
The Cooling Tube is attached on one end to the Heatsink. The Cooling Tube is normally filled with Nitrogen.
The other end of the Cooling Tube has a metal plate, or plates, attached to it.
The metal plate sits on top of the Processor's case. Some designs also have another metal plate, which sits on top of the graphics chipset.
Some do not.
The Cooling Tube absorbs heat from the Processor, and graphics chipset, then transfers the heat to the Heatsink.
The Cooling Fan draws air into the laptop through the Air Intake Duct, then flows air through, and around the fins of the Heatsink.
With some laptop cooling system designs, as mentioned above, there is no metal plate sitting on top of the graphics chipset.
The Processor, and graphics chipset are the two hardware components that put out the most heat.
If no metal plate is used to transfer heat away from the graphics chipset, the graphics chipset can overheat.
Other laptop cooling designs are inadequate in the cooling system provided, in relation to, if they do have a metal plate sitting on top of the graphics chipset.
The fan size, and/or the Heatsink's capability, are underrated in relation to taking care of both the Processor, and graphics chipset.
The Processor may receive adequate cooling, but the graphics chipset does not, and overheats.
If a Processor overheats, it turns off. (BIOS turns it off) This is so the Processor does not burn up.
Not so with a graphics chipset. It will overheat, and burn up.
Usually before the graphics chipset does burn up however, there is another process that happens.
The graphics chipset is mounted in a BGA surface mount, to the motherboard.
With the older Processors there were pins that came out of the bottom, and inserted down into socket holes in the processor socket.
With a BGA surface mount the chipset has solder balls in place of the pins.
The motherboard has matching copper pads.
The chipset is set into place on the motherboard's copper pads, then the chipset is heated until the solder balls melt.
This action solders the chipset to the motherboard.
If a graphics chipset becomes too hot, the solder begins to melt again.
The solder connections are now bad, and no graphics are displayed on the LCD screen.
Monitor is Black.
This is information on the problem above, in relation to the HP Pavilion dv2000 series, dv6000 series, dv9000 series, and a lot of other laptop computers.
Also a possible solution to repair.
(I would use a Heatgun instead)
http://www.youtube.com/watch?v=bnkQNmKauEc
If you post the Model Name, and Model Number, I may be able to find a free Service Manual for your Toshiba laptop.
(Example Toshiba Satellite P105-S9937
Toshiba: Laptop manufacturer name
Satellite: Model Name
P105-S9937: Model Number)
Regards,
joecoolvette
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