Lenovo IdeaPad 1 15ALC7, motherboard JS471/JS573 NM-E541 Power on sequence?

[L.L.]

Hello, I have this board in question. When I connect an AC-DC adapter charger (without a battery), the consumption is 19mA, with only +5VALW and 3VL present. When I press the power button, all voltages appear OK, the consumption rises to 260mA and remains stable. There's no video.

My question is if anyone has this board or information on the power-up sequence, and if the other ALW voltages are present when the load is connected.

What I noticed is that at first, 3VALW and 1.8VALW appear for a second or less. The BIOS is never read. Even so, the BIOS has been reprogrammed without success.

I have brd where, no sch.
Thank you very much to anyone who can help me.

[mon2]

Remove all power. Test the resistance to ground of each inductor. Checking if there is a short on an inductor which will force that leg of the power supply to turn off.

[pc_okay]

Not same laptop 3rd gen ryzen but might be similar…

[L.L.]

No short is measured on any coil.

Relatively low ohms on the +0.75LALW output (30 ohms and 60 ohms reverse).
Can anyone confirm this is correct?

When connecting the AC plug, the "ALW" voltages appear (3V, 5V, 1.8V, and 0.75V), but they immediately drop to 0V, leaving only the +5VALW.
Can anyone with the same board confirm this is correct? If not, can I suspect the EC?

The strange thing is that when I press the power button, all the "ALW" voltages are correct.

Note: Without a ROM BIOS chip, same behavior.

[pc_okay]

That’s weird yes…
Where do you put your black probe to get ground when you take your mesurement?
One time I was putting my black probe on the display port frame and getting thoses weird drop of voltage!

Please mesure next signals & voltage after pressing power button.

[mcplslg123]

I confirm that measurements at post#4 is correct. The ALW rails(except 5V) are supposed to go to deep sleep mode in offline mode-So they should logically disapperar after few seconds.

Is the ram soldered onboard?

[L.L.]

Confirmo que las mediciones en la publicación n.° 4 son correctas. Se supone que los rieles ALW (excepto los de 5 V) entran en modo de suspensión profunda en modo sin conexión, por lo que deberían desaparecer lógicamente después de unos segundos.

¿Tienes la misma placa y la has medido, o se supone que debería?


¿La RAM está soldada a la placa?

Sí

thank you mcplslg123

[L.L.]

I initially ruled out RAM because there were no BIOS reads at any time.

[L.L.]

Can someone with the same motherboard measure if there is output data on the "UB1" ROM IC when connecting the AC-DC adapter?

[UKBREFIX]

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