Laptop won't turn on

I'm running into an issue with an older laptop, a Dell Latitude. It was working perfectly fine just a few days ago—my brother was using it for his college courses—but after he brought it home, it suddenly went completely dead. If I leave it unplugged for a while, once I plug the charger back in, the indicator light shows it's receiving power, and when I hit the power button, the LEDs flicker for less than a second as if it's trying to boot, and then... nothing. Total silence. No lights, no response. Interestingly, if I let it sit unplugged for more than 24 hours and then plug it back in, the cycle repeats. But during that first day after plugging it in, absolutely nothing lights up.

I've already tried stripping it down—removed the RAM, HDD, DVD drive, and even the keyboard—to see if I could get a minimal boot, but no luck. Eventually, I took the whole thing apart and connected just the motherboard to the power supply. Theoretically, at least the motherboard LEDs should illuminate to show it's getting juice, but they don't. The connector linking the DC jack to the motherboard is a mess; it looks pretty bad, but honestly, it’s been like that since the last time I opened it up for cleaning. I checked the charger with a voltmeter, and it’s putting out a solid 19V, which is what it should be. However, once I plug it into the laptop and measure the voltage directly on the motherboard, it drops to a measly 8V!? I've double-checked my measurements multiple times to make sure it wasn't just a bad contact between the probe and the board, but it consistently reads 8V. There are two red wires and two black wires running from the jack to the motherboard, but those pairs are shorted together—meaning the two reds act as one and the two blacks act as one—which might be due to high current draw, though it seems odd to me.

Here are some photos:
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The connector looks pretty rough in these shots 😁 but again, it was in this state before and it was functioning. I suppose I could try replacing it. Looking at how melted it is, it looks like there might be a short between the positive and negative rails, but my instruments aren't showing a short, and nothing gets hot when I connect the charger. What else could be causing this? Maybe the charger itself is failing given the massive voltage drop when connected to the laptop, but I'm stuck on how to isolate the charger from the laptop to test them individually.

You definitely need to grab a new connector. Here’s what happened in my experience: because of a loose connection at that port, things started melting after I left my laptop plugged in for a long time. That poor contact creates high resistance, which is why when you test the board, you're only seeing 8V. Try cutting those wires—which you’ll have to do anyway once you go to swap out the connector—and then measure the voltage directly on the wires while the charger is plugged in; I’d bet money you'll see a normal reading there. The issue is definitely sitting right in that connector. If you're really stuck, you might even be able to bypass the connector entirely by soldering the wires directly to the board from underneath.

I mean, I'm probably wrong, but maybe try doing an electrostatic discharge:
-unplug it from the wall
-pop the battery out
-hold down the power button for about a minute
-leave the battery out for now
-plug the charger back in
-try turning it on normally with a quick tap of the button

Based on what you're describing, there's also a chance—this actually happened to me with my Lenovo—that the processor pins melted slightly and aren't making full contact with the motherboard anymore. If that's the case, you'd need to do a CPU reballing, which honestly probably costs more than the laptop itself, so it's usually not worth the money. There is this other option where you pull the motherboard out, stick it in the oven, and bake it at a specific temperature for a bit so the pins melt and reform... it actually works! There are tons of videos on YouTube showing how to do it. Just a heads-up though, I tried it myself and set the temp way too high and ended up frying my entire motherboard. Oops.

Well, turns out it was the connector after all. Dammit. I had a gut feeling it wasn't just that one little part, which is why I started this thread in the first place—I was convinced something on the motherboard had fried. I ended up smashing the thing, ripped the wires out, and soldered them directly onto the contacts. Now the LEDs are lighting up. When I connect just the display and the power button, the laptop kicks on, the fan spins, and the lights flash, but then it just shuts itself down after a few seconds and restarts in a constant loop. The screen stays black. I'm assuming that’s just because there's no RAM or hard drive installed yet.

Now I need to find someone who actually knows how to solder properly, because my cheap iron and mediocre skills aren't cutting it. I couldn't even get the original connector off; the solder wouldn't melt it, so I just ended up crushing the plastic—well, more like pulverizing it since it was already half-melted—and soldered the wires to whatever pins were still sticking out of the motherboard. It won't hold for long. Ideally, those pins need to be removed so I can solder everything cleanly to the board. I'll probably hit up my buddy; he's got much better gear and way more experience with these tiny micro-components.