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Laptop won't turn on?

Laptop not turning on:

Laptop won't turn on. This symptom can be relatively simple to solve, as 80% of the defects related to it are easy to diagnose even for those who are starting it.

When a laptop is not turning on, you need to perform some basic tests to diagnose where the defect is coming from.

Much of the problems that appear on laptops are not related to the motherboard, as most technicians who are starting.

But yes, there are also defects related to the motherboard that will require more specific knowledge such as basic electronics of laptop (component testing) and reading schematics.

The knowledge and tips you will read in this part, you will be able to solve or at least diagnose the laptops that reach you.

The first step is to define which symptom, they are:

1. Laptop won't turn on (no signal at all)
2. Laptop turns on and does not give video
3. Laptop turns on and off quickly.

1. Laptop won't turn on (no signal at all)

When you have a laptop on the bench that when you press the power button nothing happens (no LEDs do not turn on, the fan doesn’t turn, anyway, no signal), you will follow two lines of analysis to find the defect, they are: basic power supply laptop or defect on the motherboard circuits.

Laptop Power supply testing:

Step 1:
Check the charger.
If when connecting the laptop, it continues with the led access is a good indication that it is ok. If the led don’t light up or flashes, it means that the charger or the motherboard is shorted.

Step 2: See also the charger's output voltage.
With the multimeter on the 20v scale you will check if 18.5v, 19v or 20v is coming out, depending on the laptop model.

Step 3: Check the condition of the JACK.
The JACK is the component that receives the voltage from the charger to supply the motherboard, check if the pin is not broken, if yes, replace it.

Step 4: Test also if the voltage is passing through it and feeding the motherboard.
For this, measures on the multimeter’s DC20V scale the coil that is at the entrance, after the JACK.

Step 5: Check the condition of the Power button.
Check that there is no oxidation preventing the button pads from making contact with the motherboard, or if there is a lack of voltage.

Step 6: Disconnect all peripherals from the motherboard.
Leave only the motherboard and the charger connected and check for any changes in the initial symptom.
Sometimes a simple shorted Wifi card can cause this symptom (laptop won't turn on).

Look for defects in the motherboard circuits::

After making sure that everything is ok with the basic supplies of the laptop and even then it does not turn on, then you will really have a defect in the motherboard that needs to be analyzed.

And that is where the good part comes, as few technicians can solve this type of defect.

That would be one of the reasons why this service is more expensive.

Basically what you are going to do now is to know if all the motherboard switched sources are present.

To do this, just look for the large coils you have on the motherboard and measure with the multimeter on the DC 20V scale if they all have voltage. Why the coils and not any other component?

Simple, every laptop motherboard has some switching sources that make it start and work.
A switching source is basically formed by a PWM IC , a high and a low Mosfet , a coil and a filter capacitor .
Precisely the coils that are in these sources is where we should check if there is a voltage output.

And the main sources switched from the motherboard, form the following voltages:

  • 3V voltage (Primary PWM)
  • 5V voltage (Primary PWM)
  • 1.5V voltage (Secondary PWM - RAM)
  • 1.05V voltage (Secondary PWM - Chipset)
  • 1V voltage (Secondary PWM - Processor).
So all you need to know is whether all switching sources are working and generating these voltages so that the motherboard can turn on.
 
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