Practice Test Geeks(CMT) Certified Mobile Tech Practice Test
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Device Troubleshooting & Repair Flashcards

7 cards from real CMT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Device Troubleshooting & Repair flashcards as text

  1. A technician replaces a screen on a Samsung Galaxy and the new display has yellowish tint in the corners. This is most likely due to:

    Answer: Adhesive not fully cured after the repair

    OLED adhesive (LOCA or OCA) can appear yellowish until it fully cures under UV light or over time—this is a common post-repair cosmetic artifact.

  2. A device intermittently loses Wi-Fi but cellular data works fine. The issue persists after OS reinstall. What is the most likely hardware cause?

    Answer: Damaged Wi-Fi antenna or loose Wi-Fi module connector

    Wi-Fi and cellular use separate antennas; intermittent Wi-Fi after OS reinstall points to a hardware issue like a damaged antenna or loose RF connector.

  3. What does ESD (Electrostatic Discharge) protection during mobile repair primarily prevent?

    Answer: Invisible damage to sensitive ICs from static electricity

    ESD can silently damage semiconductor junctions in ICs causing immediate or latent failures that are difficult to diagnose.

  4. A phone's proximity sensor fails after a screen replacement, causing the screen to stay on during calls. Where is the proximity sensor typically located on modern smartphones?

    Answer: Integrated in or near the front-facing camera/earpiece assembly behind the screen

    Most smartphones integrate the proximity sensor into the front sensor bar or earpiece assembly, which can be damaged or misaligned during screen replacement.

  5. A phone dropped in saltwater is brought in for repair. After rinsing with fresh water, what is the next critical step before attempting power-on?

    Answer: Disassemble, clean with 90%+ isopropyl alcohol, and fully dry before any power attempt

    Saltwater is highly corrosive and conductive; powering on before thorough IPA cleaning and complete drying causes short circuits and accelerates corrosion.

  6. A customer's iPhone Face ID stopped working after a third-party screen replacement. What explains this?

    Answer: Face ID's TrueDepth camera module is paired to the logic board and transfers with the original screen

    Apple's TrueDepth camera system is cryptographically paired to the original logic board; the sensor assembly must transfer from the original screen to restore Face ID.

  7. When using a heat gun for phone adhesive removal, what safe practice must be followed?

    Answer: Keep the heat gun moving and use a thermometer or heat indicator stickers to avoid exceeding safe temps

    Continuous heat on one spot can cause battery thermal runaway; moving the gun and monitoring temperature prevents overheating the battery or components.