The MacBook Air M1 (A2338) is favored by many users for its slim design and efficient performance. However, even such a sophisticated device can encounter "no power" issues due to hardware failures. Recently, we received an A2338 device with board number 820-02020-A, where the user reported it wouldn’t turn on and the Type-C ports were unresponsive. In this article, China Phonefix will detail the repair process—from fault diagnosis to chip replacement—to uncover the solution for "boost chip failure," providing a reference for repair professionals and tech enthusiasts.
I. Preparation of Repair Tools
Before starting the repair, ensure the following tools are ready to improve efficiency and prevent secondary damage:
Basic Tools: Screwdriver set (including P5 Torx, T5 Torx, Phillips PH000), plastic pry tools, anti-static tweezers, suction cup.
Measuring Tools: Digital Multimeter (for voltage/resistance testing), thermal imager (for locating overheating components), oscilloscope (for waveform signal measurement).
Soldering Tools: Hot air gun (300-350°C, for chip desoldering), soldering iron (fine tip, for small components), flux, solder wire (0.3mm).
Auxiliary Resources: XZZ Schematic Diagrams (820-02020-A), A2337 timing reference document (for repair ideas).
II. Fault Diagnosis Steps
1. Initial Inspection: Eliminating Short Circuits and Power Anomalies
Disassembly and Visual Inspection: After opening the bottom cover, no obvious water damage, corrosion, or burnt components were observed on the motherboard.
Resistance Testing: Using a Digital Multimeter to measure the resistance to ground of major power supply points (e.g., PP3V3_S5, PP5V_S0) on the motherboard, all showed no short circuits (normal resistance ≥200Ω), ruling out motherboard short circuits.
Type-C Port Testing: Testing both Type-C ports revealed the left port was completely unresponsive (no current, no voltage), while the right port showed a standby current of 0.070A (normal standby should be 0.010-0.020A), indicating an anomaly in the power supply path.
2. Thermal Imaging Localization: Identifying Overheating Components
Using a Thermal Imager Camera to observe the motherboard temperature when the right port was powered on, two CD3217B12 chips (Type-C power management chips) were found to be slightly overheating (approximately 40°C; normal should be room temperature). It was initially suspected that damaged chips caused power supply abnormalities.
III. Repair Process: From Chip Replacement to Timing Troubleshooting
1. Replacing CD3217B12 Chips to Resolve Initial Power Supply Issues
Desoldering Chips: Use a hot air gun (320°C, wind speed level 3) with tweezers to remove the two overheating CD3217B12 chips and clean residual solder from the pads.
Installing New Chips: Solder new CD3217B12 Charging chips (ensure pin alignment to avoid cold solder joints), apply additional flux, and heat to solidify.
Test Results: Inserting the right Type-C port restored standby current to 0.015A (normal), and the motherboard powered on automatically. However, the current rose to 0.070A, persisted for 2 seconds, then shut down and restarted. The 5V voltage failed to boost to 12V, indicating the fault was not fully resolved.
2. Timing Troubleshooting: Locating the Cause of 5V Boost Failure
Reference to Timing Documents: According to the A2337 timing sequence, the 5V boost (PP5V0_USB_IN → PP12V_S0) requires a path through CD3217B12 → UF260 (boost chip) → downstream loads.
Key Signal Measurements:
U5200 (12V Regulator): Output voltage was 12V (normal), ruling out main power supply issues.
U5700 (3.8V Power Chip): Output PP3V8_S0 was normal, meeting core power supply requirements.
Crystal Oscillator and ROM Communication: The Y0600 (24M crystal oscillator) waveform was normal, and pin 1 of U1970 (ROM chip) showed a read waveform on SPI_SOCROM_1V8_CS_L, indicating normal communication between the CPU and ROM.
Thermal Imaging Recurrence: Re-powering the motherboard revealed the UF260 chip (marked 8N120, 5V boost chip) was slightly overheating. Combined with the "5V boost failure" symptom, it was determined that a damaged UF260 caused the boost failure.
3. Replacing UF260 Boost Chip to Fix Shutdown-Restart Fault
Desoldering UF260: Use a hot air gun (300°C, wind speed level 2) to remove UF260, clean the pad, and apply flux.
Installing High-Quality Chip: Solder a high-quality used UF260 chip (ensure no pin oxidation) and re-test power supply.
IV. Repair Validation
Standby Current: Inserting the Type-C port showed a stable standby current of 0.018A with no shutdowns.
Boost Test: A multimeter measured PP12V_S0 voltage at 12.1V (normal), confirming restoration of the 5V boost path.
Startup Verification: Pressing the power button caused the current to jump to 0.350A → 0.800A → 1.200A, and the screen lit up with the Apple Logo, indicating successful repair.
V. Repair Conclusion and Summary
This A2338 "no power" issue was caused by the combined failure of two CD3217B12 power management chips (leading to initial power supply abnormalities) and the UF260 boost chip (preventing 5V from boosting to 12V). Both are critical components in the Type-C power supply path, and either failure alone would block the startup sequence.
Key Repair Takeaways:
Thermal Imaging Utility: Quickly identifies overheating components, avoiding blind chip replacement (e.g., initially targeting CD3217B12).
Importance of Timing Checks: After initial repairs cause "shutdown-restart" issues, strict timing-based testing of power supplies and waveforms is essential to avoid missing secondary faults (e.g., UF260 damage).
Chip Quality Control: Use reliable used or new chips when replacing boost components to prevent recurrence.
Through these steps, the A2338 no-power fault was successfully resolved, validating the effectiveness of the "diagnose first, repair later" logic in repair workflows.
MacBook Air A2338: Troubleshoot No Power Issues
