820-00239-09 No Backlight

[iFix]

Hi Guys.

U8400 had damaged 4 contacts but i rewired them:
8 - NC
9 - ISNS_LCDBKLT_N
10 - ISNS_LCDBKLT_P
11 - BKLT_SD

Q8400 : PPVIN_S0SW_LCDBKLT_R - 13v and LCDBKLT_EN_L is 12.2v the others are 0v.

Also i replaced u8400 of course. Any ideas would be appreciated.

Thanks

 

[2informaticos]

Do you get image and USB activity?

 

[iFix]

Image yes, usb haven't tried since it's type c and it's powering on showing picture normal

 

[2informaticos]

Q8400 requires 0V at BKLT_SD; controlled by U8400.
Do you get 3V at BKLT_EN_R?

Check all surrounding components of U8400.
Post voltage and diode mode at BKLT_SCL/SDA; do the same for BKLT_PWM bus.

 

[iFix]

EDP_BKLT_EN is 0v.

BKLT_PWM_TCON2MLB 670 - 0.9v
BKLT_PWM_MLB2TCON 710 - 0v

BKLT_SCL/SDA both 5v

 

[iFix]

I measured again and Q8400 LCDBKLT_EN_L is 9.3v all other contacs on q8400 are 13v and on R8402 LCDBKLT_EN_L is 9.3v and BKLT_SD is 5.3v

 

[2informaticos]

BKLT_SD shouldn't drop if BKLT_EN_R is low.
You may have bad U8400 now...

 

[iFix]

Hi turns out that the lcd is bad or the flex cables from it... my repair was successful, now i need to see if possible the lcd flex to be fixed