Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

What you will do if your ac adapter for you pc doesn't work?
The most common type of AC power adapter involves a small box, with one wire to go to the computer and another wire to go to the wall. There is usually an LED light on it, to tell you that it is on. (Is it lit on yours?) By the way, Apple notebook power adapters often have an LED that is actually built into the side of the computer, not into the adapter box, so obviously it won't light up when it's not connected to the computer.

The power adapter box does several things. It lowers the voltage from the wall's 120 volts AC to typically 19 volts DC (it will be labeled with the exact voltage). It includes some power noise filtering. It often includes an automatic circuit breaker or overload detection. If this gets tripped, you can generally reset it if you unplug it from everything for a few minutes.

You can measure the voltages on your AC adapter with a multimeter. When it is unplugged from the computer but still plugged in to the wall, it is normal to find that the voltage may be 1 to 3 volts higher than the printed output rating.

Troubleshooting: AC Power adapter LED is off when you plug the adapter into the wall but not into the computer
Has it been overloaded? Is the power strip turned on / is the outlet working? Is the cord from the adapter to the wall fully plugged in on both ends (try wiggling)? Your adapter may be fried- try borrowing an indentical adapter from a friend and seeing if that one will work in it's place (but do not plug it in to your computer, or you might fry your friend's adapter).

Troubleshooting: Check output voltages with a volt meter/multimeter
For those of you with circular connectors, your task is easy. Measure the voltage between the inside and the outside. A diagram on the adapter's label will tell you which should be positive and negative.

Troubleshooting short circuits
An ohm-meter / multimeter will read less than ~3 ohms when you measure the resistance between sides of power going into a short circuit. When measuring between then power pins going into the back of your computer, consider the 2 pins where you expect voltage to be applied by the AC adapter. If the resistance indicates a short circuit, this is bad.

A common trick to help isolate possible problems is to try to removing anything that might be a short circuit. Take out the battery, the hard drive, the DVD/CD drive, the floppy drive, PCMCIA cards, USB devices, miniPCI cards. See if the computer will then turn on.