Motherboard Repair and Diagnosis

Introduction

• Urgent job to fix a Microsoft Surface laptop today.
• Customer is paying extra (total of £130) for expedited service.
• Laptop has been previously opened by someone else.
• Main issue perceived: the laptop is dead.

Initial Diagnosis

1. Power Supply and Voltage Checks

   • Laptop plugged into the original charger.
   • Light indicator is on, but no voltage on the motherboard.
   • No voltage on the main power rail; capacitors also showing no voltage.
   • Suspicion of an issue with the power supply on the board.

2. Components and Voltage Testing

   • Identified input circuit and two MOSFETs: found 15V input, but no voltage after the MOSFETs.
   • MOSFET gates are not showing the correct voltage (should be 25V).

3. Battery Checks

   • Battery itself is not charging: initially showing zero volts.
   • Connected to an external power supply to attempt charging: minor success, but still not sufficient.
   • Main board operates from battery power but does not appear to be charging properly.

4. Possible Issues Identified

   • Problem likely in power management area including MOSFETs and related circuits.
   • Battery capable of receiving some charge directly:

Detailed Diagnosis

1. Further Power Circuit Analysis

   • Checked various power supply chips and components across the motherboard.
   • Found some capacitors and coils were in good condition, but main power still absent.

2. Removal and Inspection of Board Components

   • Removed motherboard to inspect the other side.
   • Identified additional power supply components: no visible defects.

3. Chip and Diode Testing

   • Identified specific power supply chip and double Schottky diode (likely both are faulty).

Component Replacement

1. Ordering and Installation of Components

   • Ordered new chips and diodes from a specialized supplier.
   • Replacement process for the faulty chip and diode.

2. Soldering and Resistor Adjustment

   • Replaced burnt resistors to ensure proper current flow;
   • Used a thermal camera to check for any excessive heating post replacement.

3. Testing and Reassembly

   • Connected charger and checked voltage: main power rail restored.
   • Reassembled the laptop partially for a working test: success in booting to Windows.

Conclusion

• Diagnosed and fixed a complex power issue on the motherboard.
• Successful charge and power-on test.
• Emphasized gaining experience through challenging repairs.
• Encouraged continuous learning and not setting low expectations.

Final Notes

• The motherboard repair process requires patience, thorough diagnostics, and often specialized parts.
• Even successful fixes might come after troubleshooting many non-faulty areas.
• Overall, a successful repair is also an educational process.