LENOVO 310-141bk

[String2016]

I need help on this laptop lenovo 310 NM-A751 rev:1.0 , the problem is turns on but screen is black and i see flicker, so i tried replacing good screen same results, tried rehet u5 CHIP its working for a whille, but it comes back again same issue, so tried replacing U5 chip same results.I noticed that on U5 pin4 PCH_ENVDD voltage from 3.3v fluctuating.Anyone can help on this please , attached is the schematic

[String2016]

Re: LENOVO 310-141bk

Also noticed PQ801 source is shorting to gate beeping and , could it be this mosfet is the prob?anyone please help

[String2016]

Re: LENOVO 310-141bk

Anyone can help please

[String2016]

Re: LENOVO 310-141bk

PCH_ENVDD on the U5 pin4 is fluctuating voltage

[mon2]

Re: LENOVO 310-141bk

When you have the unit on, press the key caps key on your keyboard - do you see the LED toggle on / off ?

While on, if you apply a flashlight on the front face of the LCD - can you see any of the graphics on the LCD panel ?

Does an external monitor work with this unit ?

Trying to understand if the fault is with the backlight or something else on this unit.

[String2016]

Re: LENOVO 310-141bk

@mon thanks for the response the unit is working fine before until it stock for a couple of days, its working fine on external on internal screen flashing tried replacing good screen same results, notice U5 PIN4 PCH_ENVDD voltage is fluctuating

[String2016]

Re: LENOVO 310-141bk

anyone can help?

[mon2]

Re: LENOVO 310-141bk

If the enable pin for pch rail is pulsing then some current trigger must be surfacing on the logic board. Check the resistance to ground of the rail that is turned on by this enable signal.

What is the reading?

[String2016]

Re: LENOVO 310-141bk

Do you mean the R1 resistor?That is my prob i cannot find where is located

[mon2]

Re: LENOVO 310-141bk

No. Remove the LCD display.

When you see the PCH_ENVDD signal pulsing, does the LCDVDD_CON rail (pin # 20 & 21) on the LCD connector @ JEDP1 also pulse ?

[String2016]

Re: LENOVO 310-141bk

Problem solved, R1 resistor is the culprit replaced it and its working fine now