Lenovo Yoga 3 (80jh) (Board shorted by me)

[matic]

Firstly i used pre-programed one and there was also like that problem. And i would like to add that when i replaced it i saw some smoke around Q23 but i could not see exatly from where and i thougt i burned again The KBC

Have you checked the transistor Q23?
Measure the resistance between pins 26 and 27 of that pre-programmed (burned) KBC chip.

[barkinaksoy]

Firstly i used pre-programed one and there was also like that problem. And i would like to add that when i replaced it i saw some smoke around Q23 but i could not see exatly from where and i thougt i burned again The KBC

Have you checked the transistor Q23?
Measure the resistance between pins 26 and 27 of that pre-programmed (burned) KBC chip.

I checked the Q23 when system is working normaly ( i mean if i dont plug the fan,hdd and battery. There are 3.3 v both ways.
pre- programmed one, i got angry and i trew it.

[matic]

Check the resistances between listed pins of transistor Q23:
a) Between pin 1 and pin 2.
b) Between pin 1 and pin 3.
c) Between pin 2 and pin 3.

Measure the resistances to ground on pins 1, 3 of Q23.

Q23 pin count:

[barkinaksoy]

Check the resistances between listed pins of transistor Q23:
a) Between pin 1 and pin 2.
b) Between pin 1 and pin 3.
c) Between pin 2 and pin 3.

Measure the resistances to ground on pins 1, 3 of Q23.

Q23 pin count:

a)468 kΩ
b)46 kΩ
c)513 kΩ

pin1 34 Ω
pin3 46 kΩ

Best regards.

[matic]

pin1 34 Ω

. If this measurement is correct, there is a short circuit to ground on "+3VALW_PCH" power rail.

Please, recheck these measurement.

[barkinaksoy]

Sorry, i made mistake it is 34 Ω.

[matic]

Sorry, i made mistake it is 34 Ω.

If it is correct measurement, it is a short circuit to ground.
If so, the APU hybrid is more than likely damaged.

[barkinaksoy]

Sir what is it APU hybrid? This board is UMA version and i have display.

[matic]

APU hybrid is main BGA chip (processor).

Measure the resistance to ground on pin 8 of BIOS chip.

[barkinaksoy]

APU hybrid is main BGA chip (processor).

Measure the resistance to ground on pin 8 of BIOS chip.

There is 34 Ω too.

[matic]

Much too low resistance.
Try to remove the BIOS chip from the board and remeasure that resistance.
If the resistance will not change it is 99% sure bad the APU hybrid.

If you have a picture, that does not mean the APU chip is 100% good.

[barkinaksoy]

I removed the bios chip and still there is 34 Ω. I did not remove the q23.

[matic]

Unfortunately the APU hybrid is bad almost for sure.
These chips are not cheap, so the repair is probably unprofitable.

[barkinaksoy]

But when i plug the charger this short is gone. There is 3.24 volt. If i turn off computer. And if charger is still pluged still there is not short. There is too high resistance. On pin 3 there is 3.3 volt.

[matic]

But when i plug the charger this short is gone. There is 3.24 volt. If i turn off computer. And if charger is still pluged still there is not short. There is too high resistance. On pin 3 there is 3.3 volt.

The resistance measurement on the component that is under the voltage is completely wrong.

Resistance can be measured only, when the board is completely disconnected from all power sources.

[barkinaksoy]

So in this case there is not something more to check ?
Thank you so much for your help.
Best regards.

[matic]

So in this case there is not something more to check ?

Unfortunately I don't see any other option except the APU replacement.
You are welcome.