Recently I had a customer call me with a power jack problem. The jack was obviously broken and malfunctioning on his IBM ThinkPad. DC power jacks are one of the most common problems with laptops. I quickly plugged in the AC adapter and the laptop appeared to be functioning properly. I dropped off the laptop at the customers work and thought I was done.
A few hours later the customer called me back saying his laptop had no power. My first thoughts were that the power jack was damaged and something had gone wrong. After further inspection I realized that the AC adapter was also malfunctioning. The AC adapter after visual inspection had no apparent problems. After reading the DC output on the back of the AC adapter I went to test it with my multimeter. My multimeter probes would not fit into the end of the AC adapter. so to get around this problem I used a small nail. I just used alligator clips to connect the probe to the nail. That gave me the connection that I was looking for. just take the black negative lead and attach it to the outside metal part of the AC adapter. Now I set my multimeter to volts DC and proceeded to test the output voltage. The first indication was that there was no power at all on the multimeter. After wiggling the nail around a little bit I sporadically recieved some voltage on the multimeter. If you attempt this, you should use a nail that fits in snugly, not too tight and not to loose. This AC adapter was not outputting properly, and needed to be replaced. So the customer had not only a bad jack but also a bad power adapter. When I dropped off his laptop he had another one waiting with the same problem. I proceeded to taking apart the HP Pavilion DV 5000. I got about halfway through tearing it apart when I thought I better check the power supply first. This AC adapter looked to be relatively new; however it was worth the check. The output voltage was way below what the adapter was rated at. Which I believe was 18.5 V; I also saw wild fluctuations in voltage. The customer thought he needed another power jack replacement, I was happy to report to him it was just an AC adapter. However, I had already taken the laptop halfway apart. Sometimes it’s good to listen to what the customer thinks is the problem, but also don’t let that override your own troubleshooting skills. This one was kind of weird because he had two laptops with bad AC adapters at the same time. Unfortunately he must have purchased cheap AC adapters. Test the easy things before you go replacing the power jack.