Lenovo Yoga 2-11 NM-A201 - Not powering on, standby voltage ok

KenM0560 hat geschrieben:Is it possible PC112 is defective? Because PR95 and PR98 are ok and PU11 is swaped with new chip.

No, the PC112 is more than likely ok.

Why is the highlighted resistor white color? Is it turned upside down?


Remove the jumper PJ13 and measure the voltage to ground on coil PL9 in this case.

Yes the top resistor was turned upside down. I have since reversed it so the black face is upwards.

I have removed PJ13 and now the voltage on PL9 is 1.755V

Solder the resistor PR94 and capacitor PC115 to its place (they are factory not placed).
Use the values according to the schematic:
PR94= 4,7Ω/5%, package 1206
PC115= 680pF/50V, package 0402

hi matic, sorry for the delay. I had to order the components.

i soldered PR94 and PC115 to the board and now PL9 is getting 1.83V.

This is still with jumper PJ13 open. powersupply pulls 0.11A still

KenM0560 hat geschrieben:This is still with jumper PJ13 open.

So try to connect the jumper PJ13 and measure the voltage again.

with PJ13 connected PL9 is measuring 2.4V

Remove the jumper PJ13 again and load the converter with a 1.5 - 2.2Ω resistor. The resistor power rating should be at least 1W or more. Measure the output voltage in this case.

Where about would i attach the resistor? Can i use a resistor from an old board, what package would it be? or best way to find one.

Do you have an idea what is causing the higher voltage? When the jumper is disconnected the standby voltages 3v,5v and 1.8v seem ok. Is somthing from further on power sequence is raising it.

KenM0560 hat geschrieben:Where about would i attach the resistor? Can i use a resistor from an old board, what package would it be? or best way to find one.

You need to load the 1.8V power rail only for test purpose.
You need to solder that resistor on the output of converter between the output side of coil PL9 and ground.

As I said, you should use at least 1W or more powerful resistor. You will not find such resistor on the motherboard. Go to the store with electronic components and buy it.

Hi i managed to find a 1.8ohm 1W resistor from a neighbour.

I removed jumper PJ13 and attached the resistor to the output side of PL9 and to a random GND spot. The voltage on PL9 and resistor is 1.83V. This was same with jumper removed before (with no resistor).

Remove that resistor from the board, solder the jumper PJ13 back to the place.
Remove the following components from the board one by one and check the voltage on the jumper PJ13 in each case.
- Jumper PJ17
- BIOS chip
- Transistor Q29

Do you get the correct voltage (around 1,8V) in any case on the jumper PJ13?

Do you get the correct voltage (around 1,8V) in any case on the jumper PJ13?

Yes, on the side of JP13 and PL9 voltage was 1.83V, on the other side of JP13 was 2.44V

Ok i remove the resistor and connected JP13

I remove each component one at a time and test voltage at PJ13

JP17 = 2.73V
BIOS (UC6) = 1.83V
Q29 = 2.8V

When i removed the bios chip i noticed pin 8 (VCC) did not look right. So after testing i attached it correctly back in place and now PJ13 and PL9 read 1.83V.

I put laptop together and it was powering on, i tested it for a while and it was working ok. But then after say 40mins i tried to power on again and nothing.

Now it is back to same problem as before. 2.4V on PL9.. and on 8th pin on bios.

even tho reattaching BIOS pin 8 temporarily worked.

Use a thin wire and try to bridge pin 8 of the BIOS chip to the jumper PJ13.

Do i remove PJ13?

with JP13 connected there is 2.4V

No, do not remove the jumper, just solder the jump wire on it.
If the voltage in this case is still 2.4V, try to replace the BIOS chip.

Ok, i removed the bios chip again to dump bin file from it, and when UC6 is removed 2.4V is still on PJ13 and PL9. Even tho when i removed bios the first time it dropped to 1.8V

I have ordered a new bios chip and will programme the bin file to it and see if it makes a difference.

But now im confused, i dont know why JP13 is 2.4V with no bios chip on board when before it was 1.8V with no bios chip.

For security, replace PC112 = 68P_0402_50V.

@matic - i gentley heated board with 420 degrees for around 60seconds and try powering on with same results.

@machine - i swapped PC112 with same from another board and still same result. 2.4V on PL9.

If you have anymore suggestions i will try if not i will scrap the board for parts. Thank you for your contribution so far.