From Repair Mobile
How to repair Nokia N70 Music Edition
Mobile dispaly problem & LCD repair
The first thing to check in cases of complete video failure is the power status. If you can always hear your mobile fan when you turn on the mobile and now you can't it's not a video failure, it's a power (Power Supply) or main board failure. The next troubleshooting step is to connect an screen with a standard VGA connector, whether a CRT or an screen. If your mobile won't light up the screen, it's extremely likely that either the mainboard or the internal video adapter (if it's not part of the main board) has failed. If the video adapter is a discrete component and you can find a replacement for under $5, it might be worth gambling on replacing, but it's almost never cost effective to replace a main board. There is a small chance that the internal connection to the video port has coincidentally failed with the mobile's own video subsystem, but it's not all that likely. If the screen works fine, your failure is with the mobile video subsystem, which is usually contained entirely in the screen/lid assembly. There is a decent chance that one of the cable bundles (video signal or power) that run through the hinges to the video subsystem has failed, so unless the failure is obvious (cracked screen, fading in a corner, faint image, bad pixels), you should still open up the main body of the mobile as well to visually inspect the connections. The easiest problem to identify is obviously a cracked screen, but a slowly increasing number of dead spots or whole rows or columns on the screen indicates the actual screen assembly is bad. Replacing the screen is pretty much the same on most , mobile has a nice backlight design, and the real challenge is getting the lid open and removing it without breaking anything. If your screen brightness seems to flicker or sometimes is bright and sometimes almost fades out completely, even then the unit is plugged into the wall (don't get fooled by power saver mode), then you probably have a failing inverter or backlight. Between the two, the inverter is several times more likely to fail, it plays the role of the solid state ballast in modern fluorescent lights. The backlight itself is a CCFL (Cold Cathode Fluorescent Lamp) with a very long meant time between failure, while whole generations of inverters have been lemons on some mobile models, you can easily research your model on Google. I did an illustrated guide to how to replace an inverter or backlight on a Toshiba mobile; the process is similar for any mobile.
