DELL XPS L502X Notebook no booting repair

Machine model: DELL XPS L502X

Main board version number: dagm6cmb8d0erev: d
Malfunction: Notebook no booting

Maintenance process:
A DELL XPS L502X notebook, whichnotebookIf the battery is damaged, it will work directly with the external adapter. If the power cord is accidentally unplugged when the notebook is used, there will be no switch when it is turned on again.

DELL XPS L502X Notebook no booting repair Figure 1.
Insert DC power supply standby to 0, and judge that there is something wrong with standby. Remove the motherboard measurement standby Inductor without Short circuit, but diode value only has 90 or so, which is obviously low. Change the upper and lower tubes of 3\5V first.Inductor diode value has reached 400 or so. After power-on again, there is still no 3V output, and diode value has been pulled down to 0. After removing Inductor, there is no Short circuit,diode value 300+ in the post-test stage, which proves that the post-test stage is ok. With 3V Inductor,The standby chip has only slight high temperature and no large current. Test the working conditions of the standby chip, 19V VCC is normal, and LDO3.3V 5V output is normal.

DELL XPS L502X Notebook no booting repair Figure 2.

DELL XPS L502X Notebook no booting repair Figure 3.
This standby chip should first show +5V_ALW2, press Switch and then show 3.3V_ALW_ON, and then+3.3V _ AlW will come out. Now 3.3V has not come out. Push up, find 3.3V _ AlW _ on, and then measure.

DELL XPS L502X Notebook no booting repair Figure 4.
It is found that 83 pin of EC is ALW_ON, and Diode value is normal is measured. After power-on, this pin has no VCC output, which is originally the problem of EC. Measure several resistances from EC to the middle of the standby chip. No Open circuit or pin are connected, and corrode is normal.

DELL XPS L502X Notebook no booting repair Figure 5.

DELL XPS L502X Notebook no booting repair Figure 6.
EC sends the +3.3V EN2 signal to the standby chip 27 pin through PR112. If the LDO3.3V output is normal, give the VCC of the LDO to PR112 and borrow EN. From LDO3.3V of the standby chip to Jump wire to PR112 directly, plug in again, and the standby current reaches 0.011.

DELL XPS L502X Notebook no booting repair Figure 7.
Measuring Switch pin, there are already 3.3V VCC,short-circuit Switch, current up to 1.5A Switch, installing, plugging in, starting up,or so. Troubleshooting, maintenance ends here.