A+ Lab 3 — No Display: Cable, Input, or GPU?

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CompTIA Cyber Path • A+ Lab Series • Lab 3

A+ Lab 3 — No Display: Cable, Input, or GPU?

This lab teaches one of the most common support complaints: “My screen is black.” Your job is to avoid random hardware replacement, check the physical basics first, and isolate whether the issue is the monitor, cable, input selection, or a deeper display path problem.

Simulated Ticket

User reports: “My computer turns on, but the monitor stays black.”

Priority: Medium • Scope: Single workstation • Goal: determine whether the failure is caused by power, display cable, wrong input source, or an internal graphics/output problem.

Time + difficulty:

⏱ 20–30 minutes • 📊 Beginner / early A+ • Goal: observe → isolate → fix → verify.

A+ aligned Display troubleshooting Help desk workflow Local progress saved
Progress: 0%

What a Real Tech Should Ask First

  • Is the PC itself powering on?
  • Does the monitor have power?
  • Is the monitor on the correct input source?
  • Was anything unplugged, moved, or reconnected recently?

Print mode auto-shows all steps and hides the hero image + progress UI.

Computer and monitor troubleshooting themed image for A+ no display lab
Black screen does not automatically mean bad GPU. Start with what is easiest to verify.

What You Need

Hardware
Setup
  • A desktop or monitor-connected system
  • Power cable and display cable connected
Focus
Goal
  • Check monitor power and input source
  • Confirm the display cable path
  • Only consider deeper hardware after basics are verified
Common mistake:

Don’t jump straight to “bad GPU.” A black screen is often just a wrong input source, loose cable, or monitor power issue.

Real-World Translation

Why this matters:

“No display” is a common office and home support ticket, especially after desks are moved, cables are reseated, or monitors are swapped.

A real technician checks the lowest-risk, highest-probability causes first: power, cable, input, then output path.

Break / Diagnose / Fix

Break
Simulate No Display

Create a safe display issue without damaging hardware.

Option A — Wrong input source

  1. Turn the monitor on.
  2. Use the monitor menu to switch to the wrong input (for example HDMI 2 instead of HDMI 1).
  3. Leave the computer itself running normally.

Option B — Loose display cable

Gently loosen or disconnect the display cable from the monitor side, then reconnect it later during the fix step.

Confirm the symptom

The screen should stay black, show “No Signal,” or fail to display the desktop even though the system is powered on.

Diagnose
Physical Checks

Isolate whether the problem is monitor power, cable path, input, or system output.

Check in this order

  1. Confirm the monitor has power.
  2. Check the monitor’s input source.
  3. Reseat the display cable on both ends.
  4. Confirm the cable is plugged into the intended output port.
  5. If available, test with another cable or monitor.

What healthy vs broken looks like

  • Healthy monitor power → power LED is on
  • Wrong input → monitor powered, but desktop does not appear
  • Loose cable → no signal / intermittent display
  • Deeper issue → basics verified, but still no display

Look for clues

  • Does the monitor show a menu when buttons are pressed?
  • Does the system sound like it booted normally?
  • Was the machine recently moved or cleaned?
  • Did the user plug into the wrong video port?
Fix + Verify
Resolution

Restore the correct display path and verify the system is visible again.

Possible fixes

  1. Switch the monitor back to the correct input source.
  2. Reconnect and reseat the display cable firmly.
  3. If needed, test with another known-good cable.
  4. If basics are verified and still no display, document findings before escalating.

Verify

  • Confirm the desktop or login screen appears
  • Move the mouse or open a window to verify active display
  • Confirm the user symptom is resolved
Technician habit:

Only escalate after you have checked power, input, cable, and obvious output-path issues.

Write the ticket note

Use: Symptom → Checks → Actions → Result

What This Skill Maps To

  • Troubleshooting methodology
  • Display and peripheral support
  • Physical-layer diagnostics
  • Escalation discipline
  • Ticket documentation discipline

Self-Check Quiz (Unlock Next Lab)

Score ≥ 75% to unlock the next lab link. Your score is saved on this browser.

1) A user reports a black screen, but the PC tower is on. What should you check first?

2) Which clue suggests the monitor itself still has power?

3) If the monitor is on but set to the wrong input, what is the most likely symptom?

4) Which ticket note is strongest?

Next Lab

🔒 Locked until Quiz ≥ 75% and you Mark Complete
A+ Lab 4 — Printer Offline: Queue, Spooler, or Connection?

Tip: update the next lab link when the page exists.

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