Before I begin, I'd like to note that I am very unexperienced in the electronics field, so some things that may be obvious are completely unknown to me.
I recently was dealing with a laptop that would not charge, boot, or show any signs of life. After some discussion over the phone, I learned that the AC adapter's wire was frayed, and so I immediately ordered a new one. When it arrived, there was still no success in getting any power to the laptop. I proceeded to use a multimeter to test both AC adapters, and like I suspected, the old one was reading 0V. The new one, however, was reading only 15.3V on the multimeter. The adapter says it should be outputting at 19V (both on the adapter itself and on the box it came in). Additionally, the battery is labeled at 14.4V, if that matters at all.
So my question comes down to this: could the fact that the multimeter read 15.3V instead of 19V on the AC adapter be related to why the laptop refuses to show any signs of life? If not, I will probably have to start taking it apart until I get can at the power connector.
Best Answer
At first, your laptop power source may be really weird one (not likely). Some chargers do provide only lower voltage, until device that's going to be charged requests higher voltage. Good thumb of rule: if there's only two connectors (typically round one, outer one is ground), then it should provide correct voltage all the time.
If that's not the case, then either your multimeter is showing wrong readings or your power adapter is broken.
You can check your multimeter with some known voltage, for example new 9V battery.
Typically laptop power adapters provide overvoltage without any load. It's not unusual to get for example 23V from 19V AC adapter, when it's not loaded.
Your laptop charger circuit regulates whatever is coming from AC adapter to more appropriate voltage for charging battery. In the same way, battery voltage is regulated down to 3.3V, 5V and probably also 12V for computer internals (processor, memory, motherboard, display and so on).