What does it mean when the laptop adapter light blinks?

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Here I will explain why you get a blinking light on a laptop power adapter.
Here is what happens. You plug the power adapter into the wall socket and the power adapter light is solid green. Now you plug the plug to the laptop and the light on the adapter goes off, or it starts blinking. This will continue until you unplug the adapter’s plug from the laptop. So what’s going on?


Well, this is very simple. Your laptop motherboard simply has a short, or in other words it is “fried”.

How can you make sure this is the motherboard and not the power adapter? If you have at home a multimeter (if not you can pick one up for a fiver online), test the power adapter following these procedures:

Set the multimeter to show voltage and choose 20V. The adapter gives voltage that is 19V which is very close to the limit, so we can set the multimeter to the 200V range.

Place one probe inside the plug and the other probe on the cylindrical aluminium surface.

Observe what numbers the multimeter is showing on its LCD display. The reading should be about 19 Volts. 20 or 18 Volts is still normal.

Here I will show you some very technical stuff. You can skip it if you do not want to get into it.
Here is what all the laptops have inside them. It is a MOSFET, or in other words a switch that controls the power flow.

And here is why this happened. If you look in the picture below you will see a small piece of plastic with small legs. That’s right.

This is so called MOSFET. It acts as a switch on the laptop motherboard and helps make voltages that are needed for the laptop to function.

I would not blame this chip as it usually works really hard, and if it works too hard for a long time then sometimes it fails with a bang and a smoke.

The other component that can cause the power adapter light to blink is the DC jack itself. Here is an example of a DC jack place on the board that has burned and of course has a short inside.

Usually one laptop model develops this kind of fault and then many of the same model start to fail.

What should you do if you have the situation mentioned above? Well, if the so-called MOSFET has given up there’s nothing you can do about it. The laptop needs to be repaired.

In the situation where the DC jack alone is faulty you could try to use a fully charged battery that has been charged in another laptop.

How much can it cost to repair this fault? Well, this is a somewhat complicated repair so it really depends on where you live and what kind of shops are around you. Alternatively, you can do it online. Louis Rossmann would repair this fault on a Mac, though I am not sure that he will repair a PC laptop. You can check him out, as he has a website.

I could just open the laptop myself and replace the DC jack or the MOSFET. The DC jack is inexpensive and that MOSFET may cost couple of bucks.

Do you have a similar problem?


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