Yesterday, my laptop wouldn't charge when I plugged it in. The battery had drained overnight, so the laptop was unusable. I quickly figured out that the AC adapter has suddenly stopped working.
My nearby Staples had a universal adapter in stock at 20% off, so I picked it up and was soon back in business.
But then I wondered why the "old" adapter had failed. The technician at Staples said that most fail due to a broken wire near the connector that plugs in to the computer. I know that if you flex any wire enough that it will break. But this computer was kept in the kitchen at home, and the cable stayed in one place most of the time. I decided to take it apart and fix it.
Most of the repair guides for Laptop AC Adapters resolve a break or short in the wire at one of the ends of the DC cable. One even recommends that you cut off the connector, and splice a new connector on, which is silly given that no casual user has a spare connector lying around. This same guide says that if there's no voltage after cutting off the connector, the adapter is dead and you have to buy a new one. Turns out, that's not true at all.
My repair approach was different. I decided that I would crack open the adapter housing and then verify continuity from the circuit board to the connector with a DMM. But as soon as I removed the housing, I saw the problem: Cold Solder Joints. Whoever soldered the wires to the circuit board failed to thoroughly heat up both the pad and the wire. So the solder didn't flow down the via hole and fully coat the wire. This never would have passed inspection at my company.
I fired up my soldering iron and reflowed the three connections in less than two minutes. It took at least five times longer for me to break open the housing. Message to manufacturers of consumer electronics: If you won't bother to assemble the electronics properly, at least design the housings so that they're easy to take apart and put back together! I glued it back together with RTV, and it's curing as I write this.
I've fixed several items with this type of reflow repair, including a fairly expensive audio receiver. A soldering iron and the ability to use it can keep you from throwing out perfectly good electronics.