Display doesn't turn on

First thing to try is a screen self-test -- hold D through powerup.  If you don't see a series of self-test screens, the display panel is bad.

If you do, the fault lies elsewhere.

Any further troubleshooting requires that you supply the system model number (i.e., Inspiron N5110, 7348, etc.).

Run a hardware diagnostic test.

Running a hardware diagnostic test helps you identify potential hardware failure. Dell laptops, desktops, all-in-ones, and Windows-based tablets have an integrated diagnostic test that is called the SupportAssist Pre Boot System Assessment or Enhanced Pre-Boot System Assessment (ePSA).

• If the Dell computer cannot boot into Windows, run the preboot diagnostic test. To learn more, see the Dell knowledge base article How to Enter the Integrated Diagnostics (32-bit Diagnostics, SupportAssist ePSA, ePSA, and PSA).
• If the Dell computer can boot into Windows and has an active Internet connection, run the online diagnostic test that is powered by SupportAssist. To learn more, see the Dell knowledge base article How to run the Online Diagnostics and use the Diagnostics for Troubleshooting.