ASUS K53U No Power

Hi, here we have a ASUS K53U laptop with no power at all. We check the voltage of the adapter (charger), and it is 19 Volts, as it should bee. Good thing with this laptop is that it have a cover on the bottom side, that allow us to measure the Voltage on the motherboard, by placing the measuring instruments probes on the jack as assigjed on the picture with the red arrow. This plug comes from the power jack, and if everything is OK, the Voltmeter should measure 19 Volts.

That was also the case with this laptop. The voltage come to the motherboard, but the laptop won’t power up. The LED that notify when that laptop battery is charging, does not light. So, that mean that the problem is not simple, and we need to disassemble the laptop and check the power supply on the motherboard.

After we disassemble the laptop we have the motherboard on the table:

The motherboard is PBL60 LA-7322P Rev:1A. 

Examining the motherboard we notice that on resistor from the upper side is blown. That resistor have a SMD code  “100”, what means that it have value from 10 Ohms.

But, we analyze the schematic (Page 36) that this resistor is connected with Battery Charger Controller Chip ISAL6251AHAZ.

Here you can download ASUS K53 Schematic from the link below:

and the datasheet for Battery Charger Controller Chip ISAL6251AHAZ:

There on the next picture is from the motherboard schematic and show that the blown resistor is a between the Zener diode PD101 and the Chip ISL6251AHAZ.

We check the Zener diode and it was fine, and we came with conclusion that the ISL chip is faulty, because the resistor cannot blown by himself if all surrounding components are good.

We replace the ISL chip and the resistor.

After this we can do check by connecting the battery and power adapter (charger).

As we see from the picture, the seconf LED light turn RED, what mean that the battery is charging.

Now after we fix the no power problem, we only need to assemble the laptop and we are done.