Let's go over the situation where if your dc jack on a laptop is bad and is not making a connection to the motherboard then it might look like the battery is bad as well because the battery is now not holding a charge or even taking a charge. Now this has happened a lot in my shop with my customers where their dc jack goes bad, they think their batteries gone bad because is not taking a charge anymore, they got and buy a new battery and then they decide to bring their computer in because of the battery's still not charging even with the new battery, that's because the dc jack is bad. You're going to probably right in to this a lot where the battery's not charging because the dc jack is bad and until you fixed that the battery's never going to charged. So how do you test if your dc jack is bad, it's simple, plug in the ac adapter, take the battery out of the computer. If the computer doesn't power on then you know you have a problem with the dc jack. If the computer does power on you could put the battery back in and see if it charges, if the battery is not charging at this point it's pretty likely its a bad battery.
Now it can also be but it's pretty unlikely that the charging mechanism inside the computer on the motherboard is bad. Now I've done a lot of laptop repairs and I've maybe seen that one time. So I think that's a very rare situation, so it's pretty safe to say right now that the battery is bad. Now let's go over some other reasons why a battery won't be charging it could possibly be that the contacts between the battery and the motherboard are not making a connection maybe something spilled in there or there some film covering the contacts and they're not making a clean connection. One thing you can do is take a toothbrush and just scrub in between the pins of the battery there and also srub down the pins where the motherboard connection is. Make sure that you use a dry toothbrush preferably one that has not touch human teeth. Now I've also seen instances where there's just some some kind of flukiness that's happening with the computer where if you just take the battery out and you put it back in it might start charging. Maybe there was a malfunction on the motherboard or some circuit and it wasn't actually taking a charge. Try simple things before you determine that the battery is bad. You know reboot the computer, power the computer down, power back on, take the battery out, put it back in, once or twice and see what happens just doing that may fix the problem. Now if you done all of the above and you're fairly sure that the battery is bad it's time to buy a new battery.
Another one, there's four main symptoms that could go wrong with the laptop and they are:
1. Computer won't turn on
2. Components won't work
3. Computer shuts down randomly
4. Computer acts abnormally
Number one, the laptop won't power on.
Two, components in the laptop are not working malfunctioning.
Three, the computer shuts down randomly.
And four, the computer acts abnormally.
Now, we are going with these symptoms one by one. There could be more symptoms but these are the ones that I've found in my experiences. Now number one, computer won't power on. We got a laptop that doesn't power on. How can you tell if the motherboard is bad? Well, you just ask yourself why else wouldn't a computer power on? Number one, if it's on battery power, the battery is dead or the battery is bad and number two the AC adapter could be bad, so let's roll out number one.
Pull the battery out, keep the battery out of the computer for this test and then take your AC adapter and check the voltage with the voltmeter and I'm going show you how to do that right here. Take a voltmeter and what you want to test for is voltage. Put the meter at 20 volts DC and take the tip, the power jack tip. You hold your black, your negative on the outside of the tip and you put the red in the hole in the inside of the tip. Be very careful not to touch the red and the black and the tips together, otherwise it will create a short circuit. After doing these things, be sure you have 19 volts DC or just about 19 volts DC registered on your multimeter so we can know that the power adapter works. Now, just to make sure the connections is tight, kinda bend the power cord a little bit and make sure that the registered 19 volts DC on the multimeter or voltmeter will not fluctuate or move when you bend the power adapter cord a little. Okay if you're still getting 19 volts DC when bending the power adapter cord, jiggle the power adapter cord a little bit around make sure that there's no crimson wire. Now, after you bend the power adapter cord and jiggle it and you still have 19 volts registered on your multimeter, then the power adapter tip is probably good. A lot of time you know the tip will break, great in this area here, and you wouldn't get that 19 volts DC after you do that, after it's broken. So instead of just taking the whole computer apart and finding out if the laptop has appropriately good power jack, test the power adapter first.
Now another reason a motherboard might not turned on is because it's not getting power to the power jack. Power jack might be damaged, so absorb what you can from the outside and see if it's the power jack is loose or detached from the motherboard and if it is then you know you have to replace the power jack probably, but if it looks like it's secure the only way we we're gonna be able to test the power jack is to get down to the motherboard level and look it where the power jack is soldered on to the motherboard and this I cover in many of the case study videos.
Now there's a few other things that might cause a motherboard not to turn on or computer not to turn on, it could have a bad processor, but bad processor are fairly rare I would say 1 out of 75 computers are working on, it's the processor rather than the motherboard that's bad and also there's like maybe the power button on the actual laptop is broken or something mechanical like that, but again that's unlikely but you could check those things too.
2. Components won't work
Okay number two, components on a laptop won't work. For example, a CD drive or a wireless card don't show up in windows. Whether not working properly, well that could possibly be a motherboard but the way to test that is to replace that component. If your CD drive is not working replace the CD drive if it's still not working maybe the CD drive controller or the motherboard is bad. I've had that happened on a couple Toshiba laptops I worked on. I've bought a brand new CD drive put it in, still not working, still wasn't recognized by the BIOS and it was a bad motherboard. Now HP, I also had a problem of their wireless card but it wasn't the wireless cards that were bad it was the actual controller on the motherboard, that controls the card that was bad. I think it was positioned next to a chip that got real hot like the graphics chip or something like that, on the motherboard. So if you have a laptop with components not working, you replace the components and they're still not working then you might have a bad motherboard. Now how do you roll out if windows isn't causing this problem or the operating system's not causing the problem. Well, test it with a different operating systems. This is always a good test of the motherboard using like Linux distribution like knoppix or using the Ultimate Boot CD for windows. These are both bootable CD's and it's essentially testing the hardware of a laptop because you're running it on a different operating systems. Last thing to try if components aren't working and you suspect is your motherboard. Flash the bios of the motherboard, maybe the BIOS got corrupted somehow, and since the BIOS is like handles the basic functions of a computer, maybe it's not doing it's job and causing some abnormal activity in the computer.
Hope you find this answer helpful, God bless.