HP 520 LA-3491P High Side MOSFET Heat Problem

[Lex-]

1.8v rail shorted, PQ16 high side mosfet of the 1.8v rail badly damaged with a hole on the middle of it, SI4800 maybe, can´t read it, replaced with FDS8884 as indicated in the schematic, now the 1.8v rail present but PQ16 heats up a lot instantly, can someone have an idea on what to check please ?

Also disconnected PJP4 no change, PQ16 heats a lot !

Schematic:

[Lex-]

Re: HP 520 LA-3491P High Side MOSFET Heat Problem

Someone who can help me please ?

[caspian]

Re: HP 520 LA-3491P High Side MOSFET Heat Problem

check the 19v rail for being shorted to ground. If it was shorted, search the entire mainboard to see why 19v is shorted. do not plug the laptop in until the short is gone.

[khaahk]

Re: HP 520 LA-3491P High Side MOSFET Heat Problem

What is resistance from PL7 to gnd after PJP4 open?
PU11 might be dead after PQ16 shorted.

[Lex-]

Re: HP 520 LA-3491P High Side MOSFET Heat Problem

caspian:

19v rail not shorted to ground.


khaahk:

Fluke 26III, red probe connected to ground, black probe connected to PL7:

ohms scale: 0.892 k ohms

continuity (beep) scale: 149.3 ohms
Note: if I invert test probes (black to Gnd, red to PL7) then no read -OL.-

Thank you.

[Lex-]

Re: HP 520 LA-3491P High Side MOSFET Heat Problem

What is resistance from PL7 to gnd after PJP4 open?
PU11 might be dead after PQ16 shorted.

Fluke 26III, red probe connected to ground, black probe connected to PL7:

ohms scale: 0.892 k ohms

continuity (beep) scale: 149.3 ohms
Note: if I invert test probes (black to Gnd, red to PL7) then no read -OL.-

Any advice ?

Thank you.