Hi everyone,
I'm working on a MacBook Air 2020 (A2337, board 820-02016) and running into a strange USB-C issue. I've gone through quite a bit of testing and part replacement, but I'm stuck β hoping someone here can shed some light.
π Original Issue
The machine initially wouldn't negotiate 20V over USB-C β stuck at 5V.
Diagnosis showed PP1V5_UPC0_LDO_CORE shorted to ground.
I replaced U3100 (UF400) using a donor board (A2179), and the machine powers on fine now.
β οΈ New Problem: One USB-C Port Only Works in One Orientation
β’ UF400 (one USB-C port) works fine β detects a wired mouse normally.
β’ UF500 (the other USB-C port) only detects the mouse in one orientation.
β’ Power seems fine (mouse LED lights up both ways)
β’ A USB flash drive works in both directions, oddly enough
π Suspected Cause: CC Line Detection
Comparing with another known-good MacBook that uses CD3217, I found the issue seems tied to the CC1/CC2 lines, which determine plug orientation.
On the known-good CD3217-based MacBook(not A2337):
β’ No device: CC lines = 0V (pulled to ground)
β’ Device plugged in: CC lines rise to around 1.6V via Rp pull-up
β’ Resistance to ground: ~7MΞ©
β’ Diode mode: ~0.550V
On my faulty MacBook:
β’ No device: CC1/CC2 fluctuate between 1.0Vβ2.4V (should be 0V)
β’ Resistance to ground: ~7MΞ©
β’ Diode mode: ~0.550V
Mouse Test:
β’ Normal direction:
β’ USBC1_CC1 β 1.6V, USBC1_CC2 β 0V
β’ Reversed plug:
β’ USBC1_CC1 β 0.1V, USBC2_CC2 β 1.6V
β‘οΈ This confirms only one direction is being detected.
π Parts Already Replaced (No Change):
β’ Both CD3217 chips ( A2338)
β’ CF513, CF514
β’ DZF676, DZF686
Key Voltage Readings:
Signal / Point Value
C20 PP3V3_S2_UPC 3.3V
C22 PP3V3_UPC1_LDO 3.3V
E22 PP1V5_UPC1_LDO_CORE 1.5V
L18 USBC1_3V3LDO_EN 1.79V
RF901 0Ξ©, 1.79V
RF112 100K, 1.79V
CF110 3.79V
CF115 3.28V
RF100. 3.28V
Possible issue:
USBC1_3V3LDO_EN only shows 1.79V β not a full 3.3V.
Could this be preventing LDO or CC detection logic from working properly?
β Looking for Advice:
1. Should USBC1_3V3LDO_EN be a full 3.3V?
2. Besides CD3217, are there any other components that could interfere with CC line detection or LDO enable?
3. Has anyone seen a similar βone orientation onlyβ USB-C issue β and what was the cause in your case?
βΈ»
Any tips or guidance would be greatly appreciated π
Happy to provide schematics/snippets if needed.
Thanks in advance!β
I'm working on a MacBook Air 2020 (A2337, board 820-02016) and running into a strange USB-C issue. I've gone through quite a bit of testing and part replacement, but I'm stuck β hoping someone here can shed some light.
π Original Issue
The machine initially wouldn't negotiate 20V over USB-C β stuck at 5V.
Diagnosis showed PP1V5_UPC0_LDO_CORE shorted to ground.
I replaced U3100 (UF400) using a donor board (A2179), and the machine powers on fine now.
β οΈ New Problem: One USB-C Port Only Works in One Orientation
β’ UF400 (one USB-C port) works fine β detects a wired mouse normally.
β’ UF500 (the other USB-C port) only detects the mouse in one orientation.
β’ Power seems fine (mouse LED lights up both ways)
β’ A USB flash drive works in both directions, oddly enough
π Suspected Cause: CC Line Detection
Comparing with another known-good MacBook that uses CD3217, I found the issue seems tied to the CC1/CC2 lines, which determine plug orientation.
On the known-good CD3217-based MacBook(not A2337):
β’ No device: CC lines = 0V (pulled to ground)
β’ Device plugged in: CC lines rise to around 1.6V via Rp pull-up
β’ Resistance to ground: ~7MΞ©
β’ Diode mode: ~0.550V
On my faulty MacBook:
β’ No device: CC1/CC2 fluctuate between 1.0Vβ2.4V (should be 0V)
β’ Resistance to ground: ~7MΞ©
β’ Diode mode: ~0.550V
Mouse Test:
β’ Normal direction:
β’ USBC1_CC1 β 1.6V, USBC1_CC2 β 0V
β’ Reversed plug:
β’ USBC1_CC1 β 0.1V, USBC2_CC2 β 1.6V
β‘οΈ This confirms only one direction is being detected.
π Parts Already Replaced (No Change):
β’ Both CD3217 chips ( A2338)
β’ CF513, CF514
β’ DZF676, DZF686
Key Voltage Readings:
Signal / Point Value
C20 PP3V3_S2_UPC 3.3V
C22 PP3V3_UPC1_LDO 3.3V
E22 PP1V5_UPC1_LDO_CORE 1.5V
L18 USBC1_3V3LDO_EN 1.79V
RF901 0Ξ©, 1.79V
RF112 100K, 1.79V
CF110 3.79V
CF115 3.28V
RF100. 3.28V
Possible issue:
USBC1_3V3LDO_EN only shows 1.79V β not a full 3.3V.
Could this be preventing LDO or CC detection logic from working properly?
β Looking for Advice:
1. Should USBC1_3V3LDO_EN be a full 3.3V?
2. Besides CD3217, are there any other components that could interfere with CC line detection or LDO enable?
3. Has anyone seen a similar βone orientation onlyβ USB-C issue β and what was the cause in your case?
βΈ»
Any tips or guidance would be greatly appreciated π
Happy to provide schematics/snippets if needed.
Thanks in advance!β
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