My Pres C300 laptop works fine with an attached monitor. But its own LCD screen is currently having 3 equal horizontal sections. First (top) section is normal, second flickers and is normal when pressed, 3rd section is completely black. What might be the problem?

Did you plug one end in backwards?

THe screen on your laptop is faulty by the sound of it as the same processor is used for VGA out as the internal screen.
Check the cables and connectors to your screen before replacing it.
Consult a Toshiba Computer agent for confirmation if you are not sure.

Hello, It sounds like you have a bad display screen. Here is the replacement.

You have failure/weakening in the vertical section , the retrace lines appear due to the change in the freq.
Check out small value capacitors in this section. confirm by shorting parallel with the right polarity. Unless you are familiar with electronics please do not attempt unless with help. the fault is not very serious and could be attended with low expense.

If only one section of the LCD is blank/black it is defective and needs to be replaced. The condition could be Horizontal section or vertical section not showing up.

The screens are about $65 on ebay, and recommend opening to get the model number before ordering because they do change vendors and sometimes it is a AUO or Samsung or LG-Phillips.

go to the vertical section n change caps like 100uf, 2.2uf around the section in addtion check some caps in the line o/put like 22uf 250v

It sounds like your LCD is starting to go out - the screens are usually sectioned off in thirds or quarters, so when a third or a quarter starts having trouble, it's probably time to either replace the LCD, or replace the computer - because of the age of that laptop, it's possibly going to be cost prohibitive to replace the LCD. You can, however, hook it to a desktop monitor and continue using it just fine.

I can supply a brand new replacement LCD screen for £45.00 & VAT,
Sean
Require it

[email protected]

This is a problem I have seen with a few LG monitors.
Your Inverter circuit is fine (that powers the lights to your screen so you can see the image on the LCD panel) but the monitor does not like having a video signal attached to it.

1. Bad capacitors on the power board can upset the current going to the controller board. This board included the video input circuit and the power supply needs to be stable for this to operate.
2. The controller IC that translates the video signal into what the LCD panel controller can understand is failing. Normally this fault occurs in the horizontal and vertical input of the IC. The fact you can see the other message on screen is due to it going through it's own internal and seperate section of the IC. In this case the only repair option is to replace the internal video board. Sony will not supply the parts directly to the public, but if you are really nice, they "may" tell you where to get one externally to Sony.

Hope that helps =)

The problem should be dry joints in powersupply section and horizontal output section.Resolder all components mounted on heatsinks HOT Vertical O/P Ic etc.
Samir