LENOVO YOGA 900-13ISK2 NM-A921 BIOS

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LENOVO YOGA 900-13ISK2 NM-A921
BIOS LISZT (CYG41/CYG40/BYG40) NM-A921
Lenovo Yoga 900-13ISK LCFC NM-A921 Schematics

NM-A921 KB_pins=30 (JKB1) PD0=20 PD1=16 PD2=14 PD3=9 PD4=13 PD5=17 PD6=10 PD7=12 BUSY=23 STB=15 AFD=26 INIT=19 SLIN=18 KSI4=22 KSI5=21

 

[mrfraga]

Change TPD8S300

Help! lenovo thinkpad yoga l13 missing Power Ic - Badcaps

Technical discussions covering any type of laptop, notebook, netbook, tablet, or smartphone. Any and all brands and models welcome. When starting a new thread, please put the make AND model of your device in the thread title. Also be VERY descriptive of your issue, that way you'll get the best...

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[mrfraga]

This time it took 5 days for the error state to reappear and now it's not reverting back again.
The voltage across VCC-GND (pin 8-4) on the Winbond 25Q64FVIQ SPI Flash when the computer is powered on is 3.27V with 2.1mV ripple.
It's the same both in the error state and in the functional state.
The datasheet says that -0.6 to 4.6V is the maximum rating for VCC.
The voltage relative to GND doesn't exceed the maximum rating of -0.6 to VCC+0.4V on any of the other pins either.

I forgot to clarify about point 3 in the previous message; with the battery unplugged the voltage incoming from the power-adapter is still 5V, which again isn't enough to run the computer so it refuses to power on if the battery has also run out.

Here is a picture of the top right corner of the main PCB where the power connector JP23 from the external adapter is located:
View attachment 90411

Here is a close up of those smaller chips to the left of the power connector:
View attachment 90412

The markings on them are:
PQ5:
"7411 GV511C"

PQ6:
"7752 GA6D2A"

PQ11:
"7405 BA6B12"

PQ13:
"7405 BA6B12"

I can't find any information about these chips, does anyone know what they are?

I'd like to look at the datasheets for them.
If they have something to do with communicating against the power-adapter, then maybe I can look at and set registers in them with the Bus Pirate to force commands to the adapter.

 

[mrfraga]

View attachment 326420

They should to the trick.

 

[mrfraga]

Yes, the logo matches that of Alpha & Omega Semiconductor.
Thanks, they are all mosfets, in that case they are not relevant to my specific situation.

Repair Daemon; when you have the power adapter plugged into the computer, what voltage do you have across the outer pins on JP23 on the main PCB?
If you have 20V on yours and the computer still won't power on, then I guess that you and I have two different problems.

I think that the. MOSFETs are closed because of to little GDv from other power management. Look at what feeds the MOSFETs for gate.