Del latitude 3550 (LA-B071P) not powered on,
no shortage on any gray coil
Some measurements are :
1st and 2nd mosfet 20.4v
CLR 20.4v
(BQ24777)
Acdrv 25.1v
Acdet 3.14
Acok 3.1
SDA 0
SCL 0
B+ 0
so no voltage on 3v/5v ic
(also when board came no step down ic was there (TPS51285B) so temporarily used TPS51225 (only have 3v ldo always-on instead of required 3&5v Ldo always-on)
As per schematic step-down ic got B+ from charging ic, so it means charging ic faulty? It's upper and lower mos changed also but same result)
Any guidance please
no shortage on any gray coil
Some measurements are :
1st and 2nd mosfet 20.4v
CLR 20.4v
(BQ24777)
Acdrv 25.1v
Acdet 3.14
Acok 3.1
SDA 0
SCL 0
B+ 0
so no voltage on 3v/5v ic
(also when board came no step down ic was there (TPS51285B) so temporarily used TPS51225 (only have 3v ldo always-on instead of required 3&5v Ldo always-on)
As per schematic step-down ic got B+ from charging ic, so it means charging ic faulty? It's upper and lower mos changed also but same result)
Any guidance please
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