Dell cedar 13269-1 Problem - without adaptor , plugged in charging

Dell cedar 13269-1 Problem - without adaptor , plugged in charging 👉 First check vin and charging section impedance - all ok 👉 Check value of all MOSFETs of both sections - all good 👉 Connect battery and check PU4402 - it passes the battery voltage ( 2nd mosfet should be block the battery voltage ) 👉 Check PU4402 gate , it's 1.2v With battery this gate should be 13v 👉 Back trace to PQ4402 pin no 2 - its high logic ( here should be low logic in battery mode ) 👉 Back trace pwr_chg_acok and found PQ4408 PQ4408 pin no 5 gate is low logic ( in battery mode it should be high logic ) 👉 This pin (AC_IN#) connects to the charging ic pin no 5 ACOK# 👉 I just remove PQ4408 and check pin no 5 - now its high logic 👉 Replace PQ4408 from scrap board 💥 BOOM now PQ4408 pin no 5 gate is high in battery mode and low in adaptor mode, Check PU4402 mosfet gate - now gate is 13v Problem solved Copyright Case Study For Learning