220-1201 Hardware Practice Question
A user reports that their laptop display is extremely dim, but when connected to an external monitor, the image is bright and clear. The laptop is a few years old and has been used daily. Which of the following is the MOST likely cause?
⚠ Common exam trap
Candidates often confuse a backlight failure with an inverter failure; inverters are only in CCFL displays, while LED displays use a different driver circuit.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The backlight is failing.
The external monitor working correctly indicates the GPU and video output are fine. The dim internal display points to a failure in the laptop's backlight system. In LED-backlit LCDs, the backlight LEDs can degrade over time, causing dimness. Replacing the backlight or the LCD panel is the solution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The video cable is loose.
Why it's wrong here
A loose video cable would typically cause flickering, color distortion, or no image at all, rather than uniform dimness. If the cable were loose, the external monitor would not be affected because it uses a separate connection. The symptom of a consistently dim internal display while external output is normal points away from a cable issue. Reseating the cable might help if there is intermittent contact, but it is not the most likely cause here.
- ✗
The inverter has failed.
Why it's wrong here
An inverter failure would cause the backlight to not turn on at all, resulting in a completely dark screen, not just dim. Inverters are found in older CCFL-backlit laptops, but many modern laptops use LED backlights that do not have an inverter. Since the external monitor works, the GPU is fine, but the dim internal display suggests a backlight issue that could be the inverter, but it's less likely if the screen is still visible. The symptom of dimness rather than total darkness points to a different cause.
- ✓
The backlight is failing.
Why this is correct
A failing backlight, especially in LED-backlit displays, often causes gradual dimming. The external monitor works because it uses its own backlight. The laptop's display remains functional but dim, indicating the backlight LEDs are degrading. This is common in older laptops. Replacing the backlight or the entire LCD panel is typically required. This is the most likely cause given the symptoms.
- ✗
The GPU is overheating.
Why it's wrong here
GPU overheating would affect both internal and external displays, often causing artifacts, crashes, or shutdowns. Since the external monitor works perfectly, the GPU is not the problem. Overheating would also likely produce other symptoms like fan noise or performance throttling. The dim internal display isolated to the laptop panel suggests a display-specific component failure.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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