DC Jack on a Laptop

Is their a way to test the dc jack with a volt meter on ohms to see if the jack is good before unsordering it from the motherboard. Many times in the past when thinking it was a bad dc jack only to find out when I replaced the jack and go to power up to find that it was a dead mother board from the get go. As you know taking this things apart is tedious and a takes lot of time and work.

Yeah, it can be a drag taking everything apart. It is also a lot of work trying to unsolder those darn power jacks. Here's how I check things before doing all the work. First of all, remove the battery from the laptop. We don't want the battery to mask an intermittent power connection. Instead, to test if the laptop is having an intermittent power issue, power the laptop up and use the F8 key to prevent windows from booting. Let the laptop sit at the startup menu, and then start wiggling all the power connections from where it plugs into the wall all the way to the back of the laptop. If the laptop shuts off you know you have a bad connection there somewhere. If the laptop does not power on at all it too may be a power problem. However, almost always, if you wiggle the power jack or put force on it from side to side, or top to bottom you will see the ac/charging light on the laptop flicker or flash briefly. This is another sign of a problem at the power jack. Verify that the power adapter is OK. Power adapter ends are bad as often as power jacks are. Therefore, either try a different power adapter, or use a volt meter on the questionable power adapter. If you use a different power adapter, plug it in. Does the laptop power on now? If so, you know you might have a bad power adapter. But wait, also wiggle the power jack around and see if the laptop will stay on like described above. If everything is solid and you have no more power issues, you know it was a bad power adapter. If the laptop still goes in and out you know it is a power jack on the motherboard. If you don't have another power adapter to try, use a voltmeter. Most jacks have two connection points on their ends with the exception of a few adapters, especially ones used on Dells. One on the interior, and one on the exterior of the metal, male, connector. The outside is usually negative, and the inside is usually positive. If you have one of those weird Dell adapters that have a large male connector with a very small center pin then there are three connection points. The center pin is the "communications" line that tells the laptop information about the adapter. You can ignore that line. Instead, check for voltage between the outside connection on the jack and the inner side of the jack. Do not touch the communications pin in the middle. On other jacks, if you have a problem getting the meter's probe into the center of the jack, use something like a paper clip to get in there. Establish a solid connection to the jack and hold it firmly in your hands so that there is no movement where the meter is connected to the jack. Now, wiggle the wire immediately behind the jack. See if your voltmeter jumps or fluctuates. An analog meter works best for this because it is better at showing brief intermittent connection problems where as a digital meter will make it much more difficult. Obviously if you get no reading on the meter the power adapter is not putting out any power and needs to be replaced. This procedure will allow you to determine with pretty good certainty if it is the power adapter or end. Once you eliminate the possibility of a bad power adapter, and the laptop will not power on at all you could try to use an ohm meter on the laptop's power jack. If the power jack is securely connected to the motherboard you should be able to see at least some brief continuity readings at the jack. Try reversing the polarity of your meter probes if you don't get any continuity in one direction. The only way to conclusively tell if the power jack is bad or not is to visually inspect it on the motherboard. With the laptop all apart you will see physical damage where the power jack connects to the motherboard. It will be darkened, the solder will be split, and there will be obvious signs of arcing. If all the solder looks solid and shiny there is very little chance it is a power jack. However, to be absolutely sure, make sure nothing is shorting out on the motherboard and that it is not laying against anything conductive like a metal object and plug in the power adapter to the jack. Now, take your voltmeter and follow the traces back on the motherboard to the first place they connect to after leaving the power jack. Check for voltage there. If you have voltage further back on the motherboard when the power adapter is plugged in you know that the power jack is working fine.

Cool, very good info and thanks. This clears up a lot of issues and makes a good way of trouble shooting problems. Like I said in the past when taking these darn things apart and to change out a jack only to find out the jack was not the problem, imo blows and makes me want to go bang my head upside a wall This is a very good break down of checking the jacks, in the past I just flew by trial and error and most times error wins over Thanks appleoddity for you kind help Have a good day

However, to be absolutely sure, make sure nothing is shorting out on the motherboard and that it is not laying against anything conductive like a metal object and plug in the power adapter to the jack. Now, take your voltmeter and follow the traces back on the motherboard to the first place they connect to after leaving the power jack. Check for voltage there. If you have voltage further back on the motherboard when the power adapter is plugged in you know that the power jack is working fine.

The question at this point and I assume, is it safe to plug in the adapter with the mb out of the labtop case or if possible leave it in the case and if you can get to the connector points to check for voltage output do so?

I remove the motherboard completely from the laptop. Be careful with electrostatic discharge, and metallic objects that may short it out. In other words, don't leave your screw driver or any screws sitting under it. At this point the heatsinks are usually removed. So, you shouldn't be powering the motherboard up in any way unless you figure out a way to anchor the heatsinks back to the CPU and other components if they have them.