• Lenovo Z50-70 won't turn on

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#1 Lenovo Z50-70 won't turn on


by pavelsss 10 September 2019, 12:54
Hello,
my laptop Lenovo Z50-70 won't turn on when I press the power button. There are two LEDs on the front side of the laptop. The first one is indicating if the power cord is plugged in and the second one is indicating the state of battery. Both of them are off, even when the power cord is plugged in.
The power supply is fine.
Now I am checking the motherboard ACLUA/ACLUB NM-A273 Rev 1.0. After a visual inspection under microscope, there are no defects found. I've been measuring the voltages from the DC input connector (there is 20,1V), then to the first mosfet PQ301 --> 20,1V on input and 20,1V on output. Then second mosfet PQ302 20,1V on input and 20,1 on output. Then there is battery controller BQ737 (in schematic its called BQ24737). Now I will list all the controller's pins with voltages, that I've measured on these pins: 1: 20,1V | 2: 20,1V | 5: 0V | 6: 2,5V | 8: 0V | 9: 0V | 10: 0V | 11: 0V | 12: 1,7V | 13: 1,7V | 15: 1,7V | 16: 5,8V | 17: 5,5V | 19: 1,7V | 20: 20,1V|
A picture of the motherboard's related part:

Image

If somebody could point me in the right direction and advise with the next step, I would be really greatful. Thanks in advance.

Re: Lenovo Z50-70 won't turn on


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#3 Re: Lenovo Z50-70 won't turn on


by pavelsss 11 September 2019, 18:50
Ground represent by motherboard screw ESD contact
--------------------------------
Power supply disconnected, battery disconnected (no power state):

PU301 (BQ737): resistance between ground to PIN 8 = 4,1kOhm
PU301 (BQ737): resistance between ground to PIN 9 = 4,1kOhm
--------------------------------

Power supply connected, battery disconnected, free motherboard without peripheries:

PU301 (BQ737): voltage to ground of PIN 8 = 0,33V
PU301 (BQ737): voltage to ground of PIN 9 = 0,33V

Voltage to ground, PL303 = 0,05V
Voltage to ground, PL304 = 4,92V

PU904 - very high temperature (touch not possible)
PINing - look at the image, I don´t know the pinning of these package
Voltage to ground,
PIN1 = 1,15V
PIN3 = 0,02V
PIN4 = 0,05V
PIN5 = 1,23V
PIN6 = 1,13V
PIN7 = 20,45V

Voltage to ground, JRTC1(internal battery) = 3,05V

PU905 - hot temperature (touch possible)
PIN1 = 1,16V
PIN2 = 0,03V
PIN3 = 0,6V
PIN4 = 5,08V
PIN5 = 3,32V
PIN6 = 8,37V
PIN7 = 5,08V

Image

#5 Re: Lenovo Z50-70 won't turn on


by pavelsss 12 September 2019, 16:09
OFF state:
resistance to ground of PL303 = 5,77kOhm
resistance to ground of PL304 = 39,3kOhm

Opened PJ304

resistance to ground on pin 5 of PU904 = 100kOhm-180kOhm unstable

Power adapter connected:
voltage to ground on pin 5 of PU904 = 3,33V
PU904 is cold

#7 Re: Lenovo Z50-70 won't turn on


by pavelsss 16 September 2019, 19:52
KBC not replaced yet.

1.step Power adapter not connected:
I connected power source U=3V Imax=0,3A to PJ304 (opposite side of pin 5 of PU904)
Current consumption I=0,1A-0,3A unstable with power voltage 2-3V unstable.

2.step Power adapter connected:
I connected power source U=3V Imax=0,3A to PJ304 (opposite side of pin 5 of PU904)
LED4 and red LED5 shortly switch ON
Current consumption I=0,3A stable with power voltage 2V.
Temperature of IT8586E -a little warm after one minute.

3.step Power adapter not connected:
I connected power source U=3V Imax=0,3A to PJ304 (opposite side of pin 5 of PU904)
Current consumption I=0,12A stable with power voltage 3V

#9 Re: Lenovo Z50-70 won't turn on


by pavelsss 18 September 2019, 14:30
Power supply disconected, battery disconected (no power state), PJ304 open:
Resistance to ground on pins 26 of KBC(IT8586E) R=5,65kOhm

Just some additional info: computer went dead after switch on acoustic amplifier connected into headphones connector on laptop.

#10 Re: Lenovo Z50-70 won't turn on


by matic 18 September 2019, 18:26
Measure the resistances to ground on pins 4, 5, 6, 8, 9, 10, 22, 23, 39 of audio codec UA1.

#11 Re: Lenovo Z50-70 won't turn on


by pavelsss 19 September 2019, 09:52
Resistances to ground on pins 4, 5, 6, 8, 9, 10, 22, 23, 39 of audio codec UA1(CX20752-21Z), PJ304 open, power supply disconected, battery disconected (no power state):

pin 4 = 581k
pin 5 = 685k
pin 6 = 495k
pin 8 = 667k
pin 9 = 820k
pin 10 = 1M6
pin 22 = 26k
pin 23 = 26k
pin 39 = 1M3

#12 Re: Lenovo Z50-70 won't turn on


by matic 22 September 2019, 10:33
Measure the resistance to ground on jumper PJ304 (pin on the opposite side of pin 5 of PU904).
Measure the resistance to ground on pin 7 of PU905 (PU905 pin count is as indicated in the picture in post #3).

#13 Re: Lenovo Z50-70 won't turn on


by pavelsss 23 September 2019, 10:49
Power supply disconected, battery disconected (no power state), PJ304 open:
Resistance to ground on jumper PJ304 (pin on the opposite side of pin 5 of PU904): R=31R
Resistance to ground on pin 7 of PU905: R=1M5

#14 Re: Lenovo Z50-70 won't turn on


by matic 23 September 2019, 13:54
pavelsss wrote:Resistance to ground on jumper PJ304 (pin on the opposite side of pin 5 of PU904): R=31R
Remove the KBC chip from the board and remeasure the resistance to ground. If resistance will increase to the kΩ range (or grater), replace the KBC chip.

#15 Re: Lenovo Z50-70 won't turn on


by pavelsss 24 September 2019, 22:07
KBC chip removed, Resistance to ground on jumper PJ304 (pin on the opposite side of pin 5 of PU904): R=27R5

#16 Re: Lenovo Z50-70 won't turn on


by matic 25 September 2019, 20:01
Inject 3,3V from the laboratory power supply to the shorted pin of jumper PJ304. Wait a few minutes to stabilize the temperature and check, which component on the board gets warm.
Pay special attention to the small core of the APU hybrid.

#17 Re: Lenovo Z50-70 won't turn on


by pavelsss 1 October 2019, 13:41
Power charger disconnected, battery disconnected (no power state):
PJ304 - shorted
Resistance between PJ304 to ground: R=32R
Power supply U=3,3V connected to PJ304. Current consumption from power supply I=0,1A-0,16A
Termogram on pictures.
The highest power dissipation is on UA1

Image

Image

#19 Re: Lenovo Z50-70 won't turn on


by pavelsss 13 October 2019, 21:41
Since I had to remove the KBC chip, because of the testing, I can't use it again. So I was looking to buy a new one, but I am having difficulties with finding identical model "IT8586E 1435-FXA SC25NA" which is used on my nm-a273 motherboard. The only common notation I can find is IT8586E FXA, but the rest of the characters are always different. For example I found "IT8586E 1306-FXA ECZ71A".

Is there any way to obtain the original chip? If yes, where do I find it, if not, are those similar models with FXA notation compatible with my nm-a273 motheboard?

Also I don't have the opportunity to program this chip. Should I buy a programmed one, because I came across an information, that the chip will program itself after some time, when connected to power.

Thank

Photo of the original chip:
Image

#20 Re: Lenovo Z50-70 won't turn on


by matic 14 October 2019, 07:31
pavelsss wrote:So I was looking to buy a new one, but I am having difficulties with finding identical model "IT8586E 1435-FXA SC25NA" which is used on my nm-a273 motherboard. The only common notation I can find is IT8586E FXA, but the rest of the characters are always different. For example I found "IT8586E 1306-FXA ECZ71A".
The chip designation is IT8586E - FXA, all other markings are not important (it is manufacturers lot and other markings).

pavelsss wrote:Also I don't have the opportunity to program this chip. Should I buy a programmed one, because I came across an information, that the chip will program itself after some time, when connected to power.
Theoretically that KBC chip should program itself (loads the program from BIOS chip), if there are no other issues on the board.

Re: Lenovo Z50-70 won't turn on


by Google Adsense [BOT] 14 October 2019, 07:31

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