A laptop inverter is a necessary device to light up the laptop’s LCD screen. It is located within the laptop’s lid, just below the LCD. It is usually a thin but long device, made with a few electronic components. The inverter is only necessary for luminescent lamps; hence, laptops with an LED don’t have any inverter on them.
To find the inverter, you first need to know the number of the part, or to know the model number of the laptop. It is located differently on different laptop models.
On the IBM T20, it looks like long module with a two slots for cables. You can see in the picture below how it looks.
 
It is relatively quite simple to disassemble the laptop's screen. You need only unscrew a four or five screws to gain access to LCD and inverter. To understand how to disassemble the laptop screen, you could see the pictures below. This is the shortest possible guide. You can merely search on the Internet for the particular model, such as the Tecra M3 screen disassemble and you will see several images.
If your laptop inverter is causing problems, there are various indications. First of all, if the indicator fails, there won’t be any backlight at all. You will just see a very dim picture on the LCD. This is the main symptom of a failing inverter. Also, sometimes you can experience a flickering of the light when the laptop lid is turned on. This seems to happen when there is a broken lead.
Below are some pictures of a laptop inverter from various brands.
 
There are separate laptop inverter models for each laptop brand and even for each laptop model. Today, laptop inverters are already becoming a history as almost all laptops are made with LEDs.
Where to Get Laptop Inverters?
The best source for it is, of course, eBay. There are many sellers selling used laptops and laptop parts. You can even find new laptop inverters here. Even we sometimes wonder where people get their new laptop parts from. They probably must have good connections with some retailer friends!
Laptops with faulty inverters can also be repaired in local computer shops. If you are an engineer, you are easily qualified to do these jobs. But, hiring a professional means you will have to pay extra for the service.