As more and more electronics working around us, it is common sense to us that power adapters (or power supplies) are a ubiquitous part of our electronics-laden lifestyle, so does laptop power adapter. A power adapter takes the output of one power source, like a 120-volt AC wall socket, and converts it to a different output, for example a 19.5-volt power supply for a laptop. Usually these devices work dependably and without worry. With the right tool, however, you can check the output of your Sony VGP-AC19V27 AC Adapter and see if that's the source of the problem.
Set your multimeter to the proper range for measuring the output of your power adapter. Take into account the voltage and the amperage you'll be measuring. Consult the manual for specifics on how to set your particular model of multimeter.
Check the data plate of your power adapter to find out which portion of the plug is positive and which is negative. For example, on some power adapter plugs, the outer shell of the plug is positive, while on others it's negative.
Examine your Sony VGP-AC19V27 AC Adapter. Every power adapter will have the input voltage and amperage requirements printed on it, as well as the output voltage and amperage rating. We'll be testing the output of the power adapter, so write down the specs. An example would be this, taken from a laptop power adapter: Output - 19.5V....3.34 amps. We'll measure the output of the power adapter with a multimeter -- a very handy tool for anyone working with electronics. A multimeter can measure voltage, current, power output and resistance of electrical circuits by touching the electrical circuits or device with a set of probes. See Additional Resources for a good tutorial on multimeters.
Touch the probes of your multimeter to the corresponding portions of the Sony VGP-AC19V27 AC Adapter's plug and note the readout. Compare that with the rated output of the power adapter. If it varies significantly, replace the power adapter.
If possible, prepare the multi-meter before testing the laptop adapter.