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A2141 820-001700-A - Reboot at 5 V

P

Praveen Sahwal

Member
Hi,

I’ve got a MacBook Pro A2141 that is rebooting at 5V when using U3100 and U3200.

  • It stays at 20V when connected at UB300, but there is no current draw.
  • With UB400, it remains at 5V and either does not reboot or takes a long time to reboot.
I observed abnormal behaviour at U3100 — it reboots every 2 seconds. With U3200, the reboot cycle is around 9–10 seconds. I replaced U3100, but the issue remains the same after replacement.

I’ve checked most of the power rails around the power ICs, and everything appears normal. I couldn’t find any suspicious shorts, faults, or signs of liquid damage around these ICs.

Any suggestions would be appreciated.
 
2informaticos

2informaticos

Administrator
Staff member
Compare diode mode readings around all CD3217 chips; start with their LDOs.

Did you replace U3100 with one from same board model and position?
 
P

Praveen Sahwal

Member
Diode Mode reading of all CD3217.

U3100 U3200 UB400 UB300
PPBUS_G3H- 0.463
UPC_XA_DBG_PD 0.674
PP1V8_SLPS2R 0.374 0.373
I2C_UPC_XA_DBG_CTL_SDA 0.626 0.616
I2C_UPC_XA_DBG_CTL_SCL .627 0.616
SPARE_UPC_XA_USB3_RP 0.627
SPARE_UPC_XA_USB3_RN 0.750
PP5V_S4_X_USBC 0.241 0.241
PP3V3_G3H_RTC_X 0.439 0.439
PP3V3_UPC_XA_LDO 0.528 0.508
PP1V5_UPC_XA_LDO_CORE- 0.532 0.537
USB_UPC_PCH_XA_F_N- 0.508 0.506 0.506
USB_UPC_PCH_XA_F_P- 0.509 0.076 0.506 0.506
UPC_XA_SS- 0.611 0.607
UPC_XA_R_OSC- 0.494 0.498
PPDCIN_XA_G3H_F- 0.582 0.567
PPVBUS_USBC_XA- 0.168 0.199
UPC_XA_GPIO4- 0.717
UPC_XA_FAULT_L 0.702 0.681
PP3V3_S5 0.345
UPC_XA_UART_RX 0.578
UPC_XA_UART_TX 0.578
UPC_XB_SPI_MISO 0.647

U3200 has a short on USB_UPC_PCH_XA_F_P
This has been replaced but problem still persist
 
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