A2141 820-001700-A - Reboot at 5 V

[Praveen Sahwal]

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]

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

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