This IS NOT the
Laptop Power Supply


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Laptop AC Adapter or Power Supply

AC Adapter makes your laptop truly global, no matter what country you go to it will step the AC power down to the voltage you need for your laptop...

I get a lot of questions about laptop AC Adapter and power supplies such as:

  • My battery will not charge.
  • My computer will not power up when plugged in to AC.
  • My battery dies after ten to fifteen minutes.

And so on. For the most part these problems are not the power supply but either the battery or the adapter that plugs in to the wall AC outlet and then in the power connector in the case of the laptop.

Power Supplies in laptops like their counter part desktops are extremely reliable.

Normally what fails is the battery, after all it batteries do have a limited life time. That is they wear out. One way to extend the battery life time is to ensure you are depleting the battery completely before recharging.

Now this may be a little hard to do because you normally don't think or remember to let the computer run the battery all the way down. Normally you use your computer on battery in the field then you get to your office/home and you plug in the AC. If you want to do a battery depletion (run the battery all the way down) leave the computer on, if you have the battery properties set in the control panel when it gets to a certain per cent of charge the laptop will shut down. Or you could use Battery Care, a program that will "stress" the battery down to shut down of the computer.

Note: Newer laptop batteries have a built in charging/discharge circuit that will prevent a complete discharge of the battery. Because there is a small circuit board inside the battery you should NOT freeze these batteries because the lower temperature of freezing the battery will cause micro fracture of the solder for those components thus ruining a good device.

The next part that will fail before the power supply is the A.C. adapter. Now it is not a power supply it is a small transformer with a rectifier circuit that changes 120/210/220/240 volts AC to 16-20 volts DC at what ever amperage the adapter is rated for. This is one of the features that give the laptop it's global compatibility. What normally fails in the AC adapter is the rectifier circuit. Occasionally the connector/cables fail.

In my career working on laptops I have only seen two power supply failures, a lot of adapter failures and hundreds of battery failures.

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Because the newer laptops have the higher powered processors using your hand to detect a power supply that is over heating is not reliable. On older laptops if you suspected power supply problems you could feel an increase in heat in the area of the power supply.

If you know the battery is charged and the computer will not power up with the battery or the adapter then the power supply has failed.

Another indicator of a failed power supply is when you plug the AC adapter in and the power indicator does not light up. If the power indicator lights up but is a different color (normally amber or orange) and stays that way or flashes then the charging circuit is telling you the battery will not charge. (Check the owners manual for the battery charging procedures and indicators).

Bottom line on power is the first thing to suspect/change is the battery, the next thing is the adapter, last is the power supply. A good rule of thumb for a laptop is when you buy it and decide to keep it is to purchase an extra battery and a adapter. (This is a 'Best Practice' for most companies by the way).

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Now you know the AC adapter only converts the AC to DC at a lower voltage for the internal power supply.

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