Alienware m15 R5 Ryzen No Power

[Green Probe]

Hello, I have an Alienware m15 R5 Ryzen, P109f002, with motherboard GDL56 LA-K453P Rev:1.0, Ryzen 9 5900HX, RTX 3070. I got it due to it having liquid damage. I am quite new to chip-level repair, and this is my second post, so please be kind with my incompetence. The charging IC is an ISL95522ah in HPB mode as far as I'm aware. I've been using a schematic for a LA-K455PR10_0525A that is available in the forum, and it seems to match for the most part. If it's okay I can link the schematic, or insert the pertinent page into my post.

It had some crusty areas that I've cleaned up.

It had a short at the current sense resistor PRB4 after the second mosfets. That ended up being a capacitor. I removed the capacitor for now (it went to ground and had friends in parallel). I now have 170ohms to ground at PRB4.

The liquid got to the current sense resistors, so I replaced them with 1ohm resistors as per the schematic.

On the ISL95522ah charging IC:
I have 19.3v to Pin17 DCIN
I have 5.26v on Pin8 VDDP, and on Pin18 VDD
I have 5.17v on Pin12 BOOT
I have 19.7v from 19VIN to PRB9, but no only around 130mV after the voltage divider to Pin16 ACIN . From 19VIN, power goes through a voltage divider to Pin16 ACIN. The voltage divider consists of a 374k resistor (PRB9), and a 52.3k resistor to ground (PRB12). This should produce 2.4v at Pin16 ACIN. Also connected to the voltage divider for Pin16 ACIN is the drain of mosfet PQB2. The source of PQB2 is connected to ground. The gate of PQB2 goes to the EC. I get ~1.3v on the gate of PQB2.

This is where the schematic loses me. The schematic lists a MEC1515 EC, while I have a ENE KB9542QE. The schematic shows the MEC1515's PinA7 AC_DIS connected to the gate of PQB2. From my ENE KB9542QE I get ~1.3v to the gate of PQB2.

This is where the stupid questions start...

1. Does 170ohms at PRB4 after the second mosfets sound right? Still seems a bit low.
2. It sounds like the EC is supplying 1.3V to PQB2's gate, causing it to close and effectively ground the voltage divider. I'm assuming this is a safety mechanism (AC_DIS...able?). Is that right? Is there a condition that needs met for the EC to let go?
3. I suspect something GPU related is shorted. The 19v power rail before the GPU DrMOS's is 170ohms to ground, but the coils for the GPU show 0.1ohm. Considering the short is after the GPU DrMOS, and not on the 19v power rail, can I still see sings of life like charging?
4. I have a DC power supply and a thermal camera. I was able to find the shorted capacitor with just 750mV and 750mA. What is a safe voltage and current to do power injection on the GPU? I keep the voltage low and turn up current for results, but I would love some advice.
5. Extra silly question: If the GPU is shorted, Could I remove the DrMosfets or coils to the GPU to have a laptop that works on integrated graphics?

I would greatly appreciate any advice anyone has. I am in over my head, but I have a lot to gain from trying. Please let me know if I should post any more information.

Thanks!
-Green Probe

[Green Probe]

Hey guys, I'm new and have an incredibly stupid question, but I'm second guessing myself. I'm working on a laptop charging circuit on an Alienware m15 R5 Ryzen, Mobo LA-KB9542 that has had water damage. The schematic is showing the CSIN and CSIP resistors as 1_0402_1%. That does mean they are 1 ohm resistors, right? I'm getting 6.7m and 1.9m on them, and it seems suspicious for two resistors labeled as such. Any advice would be greatly appreciated!

[mon2]

1 ohm and is 1% accuracy in an 0402 SMD footprint. The values are critical as they are in the path of the current sense circuit. Always buy spares as the parts are tiny and easy to lose. Be sure to have nice tweezers + flux + use low air pressure to melt the solder and not disturb the nearby parts. Good luck and may the (hot air) force be with you.

if your measurements are correct - yes this is a root cause and will cause the unit to shut down as the current draw measurement will not match what was expected from a known good unit.

[Green Probe]

Thanks a million (ohms)! I have a feeling the liquid damage is more extensive, but this is definitely a good start. I've been using a JBC C210 knockoff soldering iron, and it seems to work a treat with the small stuff. I'm sure it won't be long before I'm back with more embarrassingly basic questions. Thanks again, mon2!

[mon2]

Ask away. We too have a JBC clone and recently brought in spare tips from Aliexpress. They appear to work well and come in assorted shapes.

[mcplslg123]

170 ohms to GND at PRB4-Clear indication of 19V rail being partially shorted. Desolder PRB4 and inject 1V/5A on the side showing low resistance. Resistance here should be in kilo ohms.

[Green Probe]

Mcplslg123, thanks for the advice. I did as you said, but it only consumes 12mA. After voltage injection the resistance on the system side of PRB4 dropped to 72ohms. I can't find a heat source with the thermal camera.

[Green Probe]

Well, I must be the luckiest noob around.

Using you guys' advice I kept looking for the short. I looked several times with my thermal camera, but it was only consuming 1V@10mA, so not much heat. After a lot more troubleshooting I tried the camera again, and found the faintest glow coming from the 19v pins on the EDP connector. The liquid damage had affected that area the worst, and some of the solder mask had flaked off leaving a bare trace, so I kept assuming it was a reflection. Turns out 2 of the 19v pins from the EDP cable were stuck inside the EDP connector. I removed the pins, and the 19v rail went to 4kohm. I tried powering it on while connected to an external monitor, but without the EDP cable connected it flashed error codes for failed CPU and failed Display. So, I tombstoned the fuse and soldered the 19v wires to it for now. "It's for testing purposes only." Until I can get a new EDP connector and cable in. Tried it again and it works flawlessly. Even the keyboard still works.

Things I learned:
-You guys are awesome! I can't thank you enough. High fives all around.
-When doing voltage injection, applying power on and off can help illustrate tiny shorts. The hot spot pulsing helps it catch your eye over reflections.
-Resistors do not like liquid damage! Every one that the liquid touched was way out of spec.
-Mobile RTX 3070 coils can totally look like a dead short, despite being healthy. I was getting 0.1ohm at most. It looked like my probe resistance. (For reference, about 50ohms on VRAM, 5ohms on CPU, 15ohms on PEX if I recall correctly. I can't remember the rest, but I'll soon get a known-good resistance reading on the coils to hopefully help someone else in the future.)
-Ryzen 9 CPUs have some crazy thermal profiles. According the the manual, it's perfectly fine for the CPU to show >100*c. Spooky.
You guys are awesome! This is a pretty huge win for me, and I'm feeling great! Lord help me, I got a gaming laptop!

All my thanks!
-Green Probe

[mcplslg123]

Yes the gaming laptop resistance to GND on coils for CPU/GPU confuses a lot of members with such low resistance. Its becoming very very difficult to differentiate what is shorted and what is not when even a resistance to gnd value of 0.1 ohms is correct on GPU. Glad to know you fixed it.