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220-1201 Practice Question: That their laptop's built-in display shows…
A user reports that their laptop's built-in display shows distorted colors and horizontal lines, but when they connect an external monitor via VGA, the external display works perfectly. What is the most likely cause?
⚠ Common exam trap
Many candidates assume any display issue is caused by a failing GPU or driver, but the key diagnostic clue is that the external monitor works perfectly, which rules out the shared components and points to the internal display path. In CompTIA A+ troubleshooting, always isolate whether the problem is with the internal display assembly or the shared video subsystem by testing an external monitor.
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 laptop's LCD panel or its video cable is damaged
The external monitor works perfectly via VGA, which bypasses the laptop's internal LCD panel and its video cable. Distorted colors and horizontal lines on the built-in display, combined with a flawless external display, isolate the fault to the LCD panel assembly or the LVDS/eDP cable connecting the panel to the motherboard. The GPU and driver are shared between both displays, so they cannot be the cause when the external display functions correctly.
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 laptop's GPU is failing
Why it's wrong here
If the laptop's Graphics Processing Unit (GPU) were failing, it would typically affect all video output generated by the system. This means both the internal LCD panel and any external monitors connected would exhibit display issues, such as artifacts, distorted images, or a complete lack of signal. Since the external monitor is confirmed to be working correctly, the GPU is likely functioning as intended, ruling out a general GPU failure as the cause for the internal display problem.
- ✗
The VGA cable is defective
Why it's wrong here
A VGA cable is specifically used to connect an external monitor to a laptop's external video output port. The built-in display of a laptop does not utilize a VGA cable for its internal connection; it uses a proprietary ribbon cable. Given that the external monitor functions correctly when connected, it confirms that the VGA cable itself is operational and not the source of the problem with the laptop's integrated display.
- ✓
The laptop's LCD panel or its video cable is damaged
Why this is correct
When a laptop's internal display fails while an external monitor works perfectly, it strongly indicates a problem with components specific to the internal display assembly. This includes the LCD panel itself, which might be physically damaged or have a failed backlight, or the delicate video ribbon cable that connects the LCD panel to the motherboard. This cable often runs through the laptop's hinge, making it susceptible to wear, pinching, or disconnection over time.
- ✗
The display driver is corrupt
Why it's wrong here
Display drivers are software components that facilitate communication between the operating system and the graphics hardware. If the display driver were corrupt or improperly installed, it would typically impact the functionality of all displays controlled by that driver. This would result in display issues on both the internal LCD and any external monitors. Since the external display is working without problems, the display driver is likely stable and not the root cause of the internal display's malfunction.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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