Lenovo yoga 3 14 /80JH/BTUU1 NM-A381/ restarts continuously

Hi ,
this laptop start , fan and keyboard light works 2 seconds , and restarts continuously

voltages on :
PL 201 is between 2,1 and 2,8v
PL202 = 5,1v
PL101=8,42v

these voltages are present only for 2 seconds when laptop start:
PL401= 1,079v ; PL801=1,7v ; PL301=1,36v

i tried other bios , ram mémory,
screen and wifi card , keyboard , battery removed
what i have to check ?
Best regards

Hello!

Measure the resistance to ground on coil PL201.
Does the voltage on coil PL201 varies in standby as well (without pressing to the power button)?

Remove the jumper PJ202 and measure the voltage to ground on coil PL201.

matic hat geschrieben:Hello!

Measure the resistance to ground on coil PL201.
Does the voltage on coil PL201 varies in standby as well (without pressing to the power button)?

Remove the jumper PJ202 and measure the voltage to ground on coil PL201.

laptop try to start when i plug
resistance to ground on PL 201 is 11MΩ sometimes drops to 6MΩ
voltage on PL201 is 2,8v but sometimes drops to 2,1v

If i remove PJ202 voltage on PL201 is 3,3v
there's a short after ?
Best regards

Place the jumper PJ202 back to the place and measure the voltages to ground on pins 1, 2, 5, 8 of PU201.

PU201 pincount (top view):

Hi
here's voltages on PU201

pin 1 = 3.9v but drops to 3.3v when laptop start 2 seconds
pin 2 = 0v
pin 5 = 3.9v but drops to 3.3v when laptop start 2 seconds
pin 8 = 8.4v

Best regards

Measure the voltages to ground on pins 2, 12, 14, 18, 21, 74, 108, 109, 124, 128 of KBC chip.

Measure the voltages to ground on pins 86, 110 of KBC chip in the following cases:
a) Power button released.
b) Power button pressed.

Hi,
pin 2 = 1,5v
pin 12 = 1,9v
pin 14 = 3,9v drops to 3,2v when laptop starts
pin 18 = 0v
pin 21 = 0v
Pin 74 = 3,9 drops to 3,3v when laptop starts
pin 108 = 0v
pin 109 = 2,9v drops to 2,4v when laptop starts
pin 124 = 0V up to 3,2v when laptop starts
pin 128 = 1,2v

pin 86 and 110 = 0v with power button pressed
pin 86 and 110 = 3,9v drops to 3,3v when laptop starts

Best regards

Measure the voltages on pins 86, 93 of KBC.
If the tensions are present, there is no dialogue with the APU.
Try another bios. Save the old version.

Try to reflash the KBC chip.

Hi

Machine hat geschrieben:Measure the voltages on pins 86, 93 of KBC.
If the tensions are present, there is no dialogue with the APU.
Try another bios. Save the old version.

i tried other bios nothing change.
There's the same voltages on pin 86 and 93:
there's 3,9v and after 2 seconds drops to 3,3v and after 2 second drop and drops to 0v after go to 3,9v continually.

matic hat geschrieben:Try to reflash the KBC chip.

Laptop try to start continually and voltage not stable , can i reflash KBC , there is no risk ?

Best regards

Go quiet and do a KBC reflash.
Save the old bios first.

I have a problem with my programmer (Vertyanov PCB v2)
it doesn't communicate with the board .
i must use keyboard connector or i can connect wire directly on the board ?

Best regards

Try to remove the jumpers PJ202, PJ206 and check, if the machine is still in restart loop.
If not, reflash the KBC chip in this case. Don't forget to save the old dump.

sebuncle hat geschrieben: i must use keyboard connector or i can connect wire directly on the board ?

No matter, in both cases it has to work.

If the programmer still doesn't communicate with the board, replace the KBC chip.
If the new KBC chip still does not change anything it is bad APU part of the hybrid BGA, which is unfortunately quite likely in your case.

Hi,
it doesn't works
i'm waiting for new KBC and i'll tell you.
Best regards

Hi ,
i check wire and tried again without PJ202 and PJ206
flash works with this files https://www.elvikom.pl/yoga-3-15-nm-a381-t49174.html.
So nothing change.
You think APU is bad ?

Best regards

sebuncle hat geschrieben:You think APU is bad ?

Yes, unfortunately the APU is bad almost for sure.

matic hat geschrieben:

sebuncle hat geschrieben:You think APU is bad ?

Yes, unfortunately the APU is bad almost for sure.

Hi ,
APU is expensive , so motherboard will not be repaired.

Thank you for your help.