Asus F541U turns on standby and power lights and nothing else MB X541UVK

Hello everyone!
The laptop is an Asus F541u with X541UVK REV 2.0 motherboard
I hope you can help me. This laptop was working but had a faulty keyboard. After disassembling it to replace the keyboard and cleaning it because it was very dirty, the laptop no longer powers up normally.

With the motherboard removed and nothing else connected, initially, when I connected the power, the charging LED would light up and draw 10 mA. When I grounded PWR_SW#, the power LED would light up but it wouldn't do anything else.

Lately, without having changed anything, when I connected the power, the orange charging LED would automatically light up, followed by the power LED, but it wouldn't do anything else. It draws 90 mA. Occasionally, when I connected the power, the white power LED would light up and the charging LED would turn off.

I measured the voltage across the main coils and I have:
PL8901 (P_CHG_RSENS_SHAPE)... 0,84V
PL8302 (+1.0VSUS) ... 1V
PL8101 ( +VCCGT) ... 0v
PL8102 (+VCCCORE) ... 0V
PL9301 (+FBVDDQ) ... 0V
PL8600 (+1.2V) ... 0V
PL8701 (+3VA_DSW) ... 3,3V
PL8702 (+5VSUS) ... 5V

Can someone please help me?

Thanks

Start by checking the RAM supply voltages:

PJP8600 (pin 1) – should read 2.5 V (VDDQ)

PJP8602 (pin 1) – should read 1.2 V (VDD)

Add the exact motherboard model and revision to your post – you might have a different board version.

Also, measure directly on the RAM slot for accuracy:

pins 258, 259 – 2.5 V

pin 241 (example) – 1.2 V

If both voltages are present and stable, proceed with further diagnostics.

Hello, thank you very much for your response and help, and I apologize because I thought I had included all the motherboard information.

The initial post has been edited and information about the X541UVK REV 2.0 motherboard has been added.

ado писал(а):PJP8600 (pin 1) – should read 2.5 V (VDDQ)

PJP8602 (pin 1) – should read 1.2 V (VDD)

PJP8601 (+1.2V) .... 0,09V
PJP8602 (+2,5V) ... 2,5V

ado писал(а):pins 258, 259 – 2.5 V

pin 241 (example) – 1.2 V

Pins 257, 259 .... 2,5V
Pin 241 .... 0,09V

I'm going to check the +1.2V line.

EDIT: I've opened PJP8601 and I still see continuity between +1.2V and P_1V2_VO_S.
How could this be?

On the PR8607, I have 19V on one side, and on the other side, which goes to pin 9 of the PU8600 P_1V2_TON_10, I have 0.77V.
On the PQH8601, between G-S (pins 16 and 17 of the PU8600), the resistance is very low at 1Ω.

PU8600 is bad?

Zemog писал(а): I've opened PJP8601 and I still see continuity between +1.2V

Desolder PL8600 and measure the resistance on both sides to determine where the low resistance is coming from.
You can also perform a short injection test on the side showing the short – just make sure not to exceed 1V during the test.
I suggested a short-circuit test in post , because the issue might be caused by a shorted MOSFET, a faulty capacitor on the line, or the IC itself (PU8600 – the buck converter controller for the +1.2V rail). You can also try desoldering PqL8602 and repeat the measurements. If the short remains after that, PU8600 is likely to culprit

I don't think I explained myself well.
On the PJP8601, with the pad open, if I check the ground, everything is correct. However, if I place one lead of the multimeter on pad 1 of the PJP8601 and the other on pad 2, the resistance is very low, as if the jumper weren't open.

Zemog писал(а): I've opened PJP8601 and I still see continuity between +1.2V and P_1V2_VO_S.
How could this be?

I'll answer that myself. It was just a matter of paying attention to the schematic and seeing that the PR8609 was the cause of this low resistance between the pads.

The device is now working. Because it sometimes worked randomly, I cleaned the DDR memory bank again (although it had already been cleaned previously and nothing unusual was observed).

After this cleaning, the device started working without problems, so it's possible that there was a short circuit on some of the pins, which is why it wasn't generating 1.2V.

Thank you very much.