Lenovo Legion 5 15arh05 NM-D281 REV1.0 mobo

[ukpicasdo]

State: when power button pressed white power button led lights up for 10sec the off for 8sec and then back on for 10 and that is happening in the loop. When charger connected charging light is on battery is charging. Checked with mmeeter. Done some basic fault finding but no luck. I've reprogrammed bios. No good. I want to start from scratch. Please guide me what to measure first cause I'm lost now. Thanks.

[Sephir0th]

Simply everything. A overview of the whole board, resistances to GND and voltages of all easy accessible power rails would be a good start.

[ukpicasdo]

Attached voltage and resistance on each coiI and also boardview for this mobo. When powered on voltage does not change. Looks to me that I got 1.2V missing. RT8231A voltage regulator. What should I do next ?

[MOD EDIT] Link to schematic - https://www.badcaps.net/forum/troubl...ion-5-15arh05h

Reminder: rules and organization of this section - https://www.badcaps.net/forum/troubl...f-this-section

[mcplslg123]

PU2701 is your ram IC.Check whether you have voltage on pin7/8(after pressing power button). Pin12 VDD is present or not.PR2711-voltage on both sides. Do check whether 3/5V ALW rail is switched to 3/5v VS.

[ukpicasdo]

Attached results for PU2701 and PR2711 resistor after pressing power button.
Just not sure how to check whether 3/5V ALW rail is switched to 3/5v VS. Can you advise?

[mcplslg123]

Enables are missing for ram regulator.SLP_S3/SLP_S5 both are missing as PCH is not responding. DC-dc transfer of 3v/5v to 3v/5v VS must be checked. Without schematics i cant confirm where is the conversion circuit.You need to look at mb closely-its not that difficult to locate it on mb.

[ukpicasdo]

I found schematics. Attached. Check if you can guide me how to check dc-dc transfer 3v/5v to 3v/5v VS?

https://www.badcaps.net/forum/troubl...16#post3169416

[mcplslg123]

Refer to page62 of linked diagram.

[ukpicasdo]

I have checked UX2. 3VS and 5VS not present. Does that mean UX2 is faulty or rather that switch is not being enabled due to lack of signal on EN1 EN2? I also recorded video of actual boot loop on this mb like https://youtube.com/shorts/duwQGyFZx...fwlGCsR2fvRHZu

[mcplslg123]

Without Enables,UX2 will not convert 5V ALW to 5V VS. With no power attached,measure resistance to GND on

pin1-2/6-7/8-9/13-14/5 of UX2

Similarly check other dc-dc conversion circuits for resistance to GND.

Idea is to check if there is anything shorted

[ukpicasdo]

Resistance to GND

pin1-2 (3.7k)
6-7 (14.1k)
8-9 (94k)
13-14 (6.6k)
5 (88k)

Doesn't look like anything is shorted here.

[ukpicasdo]

I got SUSP signal on the various points of the board but no SUSP# on pin 124 of kbc UE1

I will also check as advised resistance to GND for other dc-dc circuits bit ater.

[ukpicasdo]

I have read few other posts about missing SUSP# and according to some info if EC is not outputting SUSP# signal EC is faulty? Would that be final diagnose? EC need to be replaced? On the other hand isn't SUSP# coming on only during certain phases of booting sequence? I also saw video on YouTube guy soldering a wire from +5V to EC1 and EC2 and laptop did boot, however I am not sure if that is safe solution because #SUSP signal should not be there permanently?