220-1101 Question 178
Single answerLiquid crystal display (LCD)A user reports that their laptop powers on and boots into Windows, but the built-in LCD appears extremely dim. When the technician shines a flashlight at an angle against the screen, the desktop is faintly visible. An external monitor connected to the laptop displays normally. Which component is the MOST likely cause of the problem?
- A
Failed LCD backlight or backlight power circuitry
- B
Defective GPU on the system board
- C
Incorrect display resolution setting in Windows
- D
Failed Wi-Fi antenna routed through the display assembly
Show answer and explanation
Correct answer: A
Explanation
This scenario tests recognition of a common laptop LCD symptom: the flashlight test. If a faint image is visible only when light is shined on the display, the LCD panel is still producing an image, but the backlight system is not illuminating it properly. In modern laptops, this usually points to the backlight itself or associated display power circuitry rather than the GPU. A working external monitor is a key troubleshooting clue because it helps isolate the issue to the internal display assembly. CompTIA A+ Core 1 objectives expect candidates to distinguish between display panel issues, backlight problems, cable issues, and graphics subsystem failures using practical troubleshooting observations.
- A. Correct.
Correct. A very dim image that is still faintly visible with a flashlight is a classic symptom of a backlight problem in the laptop display assembly. On LCD-based laptop screens, the image can still be generated by the panel, but without proper illumination from the backlight or its supporting circuitry, the screen appears nearly black. The fact that an external monitor works normally also indicates the system is rendering video correctly, pointing away from the GPU and toward the laptop's internal display illumination components.
- B. Incorrect.
Incorrect. If the GPU were defective, video problems would typically affect both the built-in display and the external monitor, or would cause broader artifacts, instability, or no video output at all. Because the external monitor works properly and the faint desktop image is visible on the laptop LCD, the graphics subsystem is most likely functioning.
- C. Incorrect.
Incorrect. An incorrect resolution setting can cause stretched images, black borders, or an unsupported display mode, but it does not usually make the screen so dim that a flashlight is needed to see the desktop. The flashlight test specifically suggests the image is present but not being illuminated.
- D. Incorrect.
Incorrect. A Wi-Fi antenna issue can affect wireless connectivity, especially because antennas are often routed through the laptop display bezel, but it does not cause a dim LCD image. This distractor is plausible because the antenna is physically located in the display assembly, but it is unrelated to screen brightness or backlighting.