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Difficulty: MediumMobile Device Hardware and Display Issues

A technician completes a motherboard replacement on a smartphone. Following the repair, the device vibrates and plays notification sounds upon powering on, but the OLED screen displays no image. Additionally, the phone displays 'No Service' and fails to connect to the cellular network, even though a known-good SIM card is installed. Which TWO of the following actions should the technician take to resolve these issues?

  1. Contact the cellular carrier to update the network registration with the new motherboard's IMEI.Answer
  2. Inspect and securely seat the OLED screen's display ribbon cable connector on the motherboard.Answer
  3. C
    Replace the high-voltage backlight inverter board connected to the display assembly.
  4. D
    Reprogram the SIM card to update the device's stored IMSI number to match the new motherboard.

Answer

The technician should contact the cellular carrier to register the new motherboard's IMEI and securely seat the OLED display ribbon cable on the motherboard.
Replacing a smartphone motherboard alters its unique hardware identifier (IMEI), requiring update with the service provider to re-establish cellular access. Additionally, a blank screen on a device that boots successfully with audible prompts points to a disconnected or improperly seated display ribbon cable. Addressing these two root causes resolves both symptoms.

Step-by-Step Solution

1
Diagnose the display failure using hardware architecture principles.
Checking the internal display ribbon cable ensures proper signal and power transmission to the screen.
OLED panels emit their own light per pixel and rely on direct motherboard data connections rather than backlight inverters.
2
Diagnose the cellular network registration failure using device identifier roles.
Providing the cellular carrier with the new International Mobile Equipment Identity (IMEI) enables device authentication.
The IMEI is a unique hardware identifier bound to the motherboard. Swapping the board changes the IMEI required by the carrier network.

Key Concept

Mobile device hardware identifiers (IMEI vs IMSI) and OLED display troubleshooting.
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Topics

Mobile Device Hardware and Display Issues

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