Lenovo ideapad L340-15API is no backlight

[Nyashman]

Hi I have a problem with my Lenovo ideapad L340-15API there is no backlight and the LCD seems not to show anything, but I tested the laptop with an external monitor it works. I have tried to flash a new bios but it did not work. I tested the LCD power circuit and backlight power circuit I am getting the right voltages for both. I tested my screen and cable on another laptop and it works fine. So I don't know what to do now I am now suspecting the CPU, should I reflow the CPU?????

[Techtiger]

Re: Lenovo L340-171RH no backlight

Hi I have a problem with my Lenovo ideapad L340-15API there is no backlight and the LCD seems not to show anything, but I tested the laptop with an external monitor it works. I have tried to flash a new bios but it did not work. I tested the LCD power circuit and backlight power circuit I am getting the right voltages for both. I tested my screen and cable on another laptop and it works fine. So I don't know what to do now I am now suspecting the CPU, should I reflow the CPU?????

What voltage you get JEDP1 pin1 21 23

[Nyashman]

Re: Lenovo L340-171RH no backlight

Pin 1= 11.23V on battery 19.56V on charger

Pin 21= 3.33V

Pin 23= 3.33V
That is what I'm getting

[Techtiger]

Re: Lenovo L340-171RH no backlight

Pin 1= 11.23V on battery 19.56V on charger

Pin 21= 3.33V

Pin 23= 3.33V
That is what I'm getting

If you have the schematic uploaded it in schematic section & for data & clock dispoff ?

[Nyashman]

Re: Lenovo L340-171RH no backlight

[QUOTE=techtiger;1263573]If you have the schematic uploaded it in schematic section & for data & clock dispoff ?

I uploaded the schematic look at page 17

MOD Edit: Link to schematic https://www.badcaps.net/forum/showthread.php?t=102633
Reminder ,rules and organization of this section https://www.badcaps.net/forum/showthread.php?t=117483
.

[Nyashman]

Re: Lenovo L340-171RH no backlight

For dispoff I have 0V
dmic data = 3.22V

[Techtiger]

Re: Lenovo L340-171RH no backlight

Merci voltage on SIO pin 119? 109?

[Nyashman]

Re: Lenovo L340-171RH no backlight

Sorry what do you mean

OK I get it let me check

119= 0

109= 3.31v



[Mod. Edit-Vesko356] Use if you want to add something instead of posting a new reply!

[Techtiger]

Re: Lenovo L340-171RH no backlight

Voltage on U14 all pins ?

[Nyashman]

Re: Lenovo L340-171RH no backlight

there is 3.32V on both the bottom pins and 0V on the top pin which is ground


Edit

I fixed it the cpu just needed a reflow and it worked.
Thank you techtiger for the support