Troubleshooting Laptop Power Issues
By Stephen Bucaro
You plug your laptop in the wall outlet and turn it on and - nothing. One of the most frequent
causes of a totally dead laptop is a defective power adapter. In this article you learn how to
determine if your laptop's power adapter is defective.
A laptop power adapter consists of an AC line cord plugged into a power inverter with a DC
line coming out the other side that plugs into the power port on the laptop. Most people
refer to the power inverter as the "brick". I usually call it the "anchor" because when I move it,
it feels like I'm dragging an anchor.
The function of the power adapter is to convert AC power from a wall outlet into DC power
for the laptop's circuitry. Because it takes the negative side of the alternating current sign
wave and flips it over to be positive, it's sometimes called a power inverter. It also reduces
the voltage level and cleans up the signal.
In a desktop computer the power inverter is inside the computer's case. But because the
power inverter generates considerable heat, and the designers don't want that heat inside
the laptop case, a laptop uses the power brick configuration.
Laptop Power Adapter Troubleshooting
Now, I've been troubleshooting electronics for a long long time so I can tell you almost all
problems end up being something stupid. For example at my house some of the AC outlets
are switched by a wall switch. This is so that you can plug a lamp in them. Now if the switch
was turned off and someone had their laptop plugged into it for a few hours, their laptop
battery would totally discharge, their laptop shutdown, and they wouldn't have a clue as
to why. The moral of this story is - always check the obvious stuff first.
1. Make sure that you're getting AC power from the wall outlet.
2. Make sure the cable going into the adapter is secure.
3. Make sure the cable coming out of the adapter is securely plugged into the laptop.
4. Is the light on the power supply brick lit?
5. Lightly wiggle the plug where it plugs into the laptop. Many people, when they carry
a laptop leave the adapter plugged into the laptop, causing the connector to break inside the laptop.
One side of the brick has the adapter specifications printed on it. It usually lists the
required input voltage as being between 100-240V. This is so you can use the adapter in
other countries that use different voltage than the 110V used in the U.S. It also indicates
the polarity of the DC plug. The outside of the plug is usually negative and the inside positive.
With the adapter plugged into the wall outlet, you can use a multimeter to check the output
of the adapter. With the multimeter set to the appropriate range, put the positive (red) probe
in the center hole of the plug, and touch the negative (black) probe to the outside of the
plug. Do not let the metal of the two probes touch while connected to the plug.