Dell latitude E7240 not turning on if adapter plugged in

[shakib200]

Laptop turns on only on battery but if I plugged the adapter with battery, it is not turning on. After turning on the laptop using only battery (no adapter plug in), then plugging the adapter everything works fine also charging ok. Anyone have any clue what’s wrong?

[mcplslg123]

Mention mb markings and link schematic,if available.
Adapter is dell genuine? Bios screen shows adapetr detected properly?

[Chaminda4191]

Check pin 20 of PU700 for B+ voltage without the battery. If the voltage is missing, there may be a fault in PU800 or the +DC_IN_SS path (PD701)

[shakib200]

19v present on current sensing resistor but not present on any other parts on motherboard. 800mV present on main 19v lines.

[mon2]

Post #2

[shakib200]

B+ voltage present.. No short in +DC_IN_SS path.. Adapter detected property in bios..

[mon2]

Board is LA-9431P ?

Remove all power. Meter in resistance mode.

Measure the resistance across the following DCin mosfet pins of PQ700:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement.

[shakib200]

Board is la-9431p
All Resistance of PQ700 over 300 kohm. Why main power rail not present when adapter plugged in? No short found yet.the board Only works on battery.