LCD TV with the panel removed, showing the grid of lit LED backlights
Generic photo: RobertKuhlmann · CC BY-SA 3.0

Field pattern: TV has sound but a black screen (flashlight test before the main board)

If a faint picture shows under a flashlight, the panel and main board are working and the backlight is the fault: failed LED strips, an LED driver or the power board's backlight output. The wrong turn is ordering a main board or T-con because the screen is black; the flashlight test takes a minute and points to the right section. Also rule out the source and settings first.

Cross-checked ~30 min moderateBrands: Samsung, LG, Vizio, TCL, Hisense, All

Before you start

  • The power supply board can hold a dangerous charge after unplugging; do not touch it until discharged and verified
  • Backlight drivers run at high DC voltage; live measurements only with insulated probes and one hand
  • Lay the TV face down on a soft, clean surface; panels crack easily
  • OLED TVs have no backlight; this test does not apply to them

Diagnostic steps

Unlock all 6 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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Field pattern: TV has sound but a black screen (flashlight test before the main board) · OnCall Tech