CompTIA A+ Core 1: Chapter 12 Lab
Mobile Device Diagnostics Bench
Diagnose real mobile faults: gather evidence, test your theory, apply the right fix, verify the result
A Mobile Isolation Techniques (Objective 5.5)
Tests that isolate the real cause
- 1Cross-device swap. Try the same cable/SIM/accessory on a known-good device, or a known-good cable/accessory on the faulty device. Whichever side still fails is where the fault lives.
- 2Isolate the variable. Remove one factor at a time (case off, charger unplugged, protector removed) and re-observe before touching hardware.
- 3Battery health check. Read the device's own battery-health/cycle-count report before assuming a software cause for battery symptoms.
- 4Safety first. A visibly swollen battery is a fire/chemical hazard. Never press, bend, or puncture it. Power the device off and route it to certified service.
Why the order matters
- 1A fix chosen before you isolate the cause is a guess. Replacing a battery when the fault is a setting wastes a repair.
- 2A theory that ignores the evidence you gathered is still a guess, even if it sounds technical.
- 3Testing separates a real cause from a plausible-sounding one. A disconfirmed theory sends you back to Theory, not forward to a fix.
- 4The repair should directly address the CONFIRMED cause.
- 5Never call a fault resolved until you have verified the device end to end.
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B Live Device View
Reported symptom
1. Investigate
2. Theory
3. Test
4. Repair
5. Verify
Step 1: Investigate
Gather evidence before you guess. Run at least 2 checks, then continue.
Findings
No findings yet.
Step 2: Establish a Theory
Pick a theory. It must be grounded in evidence you actually gathered; a theory is locked until its evidence is on the board.
Step 3: Test the Theory
Run the test before you touch anything. A disconfirmed theory sends you back to Step 2.
Step 4: Repair
Pick the fix that addresses the CONFIRMED cause. A fix that does not match the cause solves nothing.
Step 5: Verify + Prevent Recurrence
Pick a real preventive measure, then verify the device is fully resolved.
Exam Tip