Hi everyone,
I know that this is likely a futile endeavor, but I have a defective (yet optically pristine) laptop mainboard here which I would very much like to repair if possible. The CPU and GPU are still pretty powerful (i7 4720HQ, GTX 960M) and a replacement would be uneconomical, so it's at least worth a shot.
Due to the nature of the failure, there may be a glimmer of hope: It conked out under full load while running a game, drawing nearly peak power (around 100W). Now it is completely dead, not even the battery indicator light will turn on when I connect the AC adapter. I am therefore hoping that the issue is related to power delivery. The first thing I tried was unplugging the battery. Then I tried swapping the AC adapter and using this device's adapter with another device. The AC adapter works fine, but I noticed 2 things when plugging in the other (different model) AC adapter: It started chirping in ~1s intervals. Also, The original adapter (which is not chirping) will provide 19V when freshly plugged into the wall and its voltage permanently drops to a random low value (such as 3V or near zero) when I plug it into the defective board. It does not have a "smart" pin btw, so I am a bit curious why there are 6 wires coming from the jack.
I am not an electrical engineer, but experience leads me to suspect something shorted out? I therefore measured for continuity at the power jack, but my multimeter says it's an open circuit. However, since 2 wires become 6 at the board, there might just be some "smart" wizardry going on and the short circuit may only occur once 19V are delivered? The 3 cell battery also seems to be very "smart" with 10 wires coming from it and only like 0.01V coming from the 3x2 cell wires while it is unplugged.
The machine saw some heavy use over the last ~3 years, but the CPU was slightly undervolted, the GPU was mostly underclocked, high performance thermal grease was applied, the fans were regularly cleaned and operational and the laptop was even propped up a bit in order to reduce heat/strain, so I don't believe the CPU or GPU died.
I finally poked a few components such as the VRMs with my multimeter leads and didn't get any readings I would consider suspicious, but I don't really know enough about electronics to analyze the readings. I DO know that you can't really measure much while a component is still mounted though...
Does anyone have a suggestion what I could try next? It would be much appreciated. Besides the multimeter, I have a soldering iron with fine tips and enough experience to remove the bigger components. I do not have any tools for SMD stuff, but I know someone who could help me out with that if there's something worth trying. The images below are as high-res as the board rules will allow, if you need better quality let me know and I will upload them somewhere else.
Thanks in advance!