820-02020 no backlight

[Dave35]

hello,

820-02020 liquid damage on few spot, i have image.

-FP800 ok
-QP800 ok
-PP5V_SW_LCD ok
-PP3V3_SW_LCD ok

-VIN ok on UP800
-BKLT_EN_R present (1.8v)
-All trace ok on UP800
-Diode mode ok on motherboard pad UP800
-All resistances tested near UP800 and QP800
-2 good screen tested
-Change Up800, backlight back few minutes only, never back again.

No voltage on PPVOUT_LCDBKLT

Any idea ?

thanks

 

[2informaticos]

Apart of enable, UP800 requires good communication with M1 and LCD assembly, through I2C_BKLT_SCL/SDA lines.
Check voltage and diode mode on that bus.
Be sure RP850-53 and their traces are good.

Also check continuity between DP800 and RP831.

 

[Dave35]

in diode mode : .460 on I2C_BKLT_SCL/SDA screen plug .473 with screen unplug
traces good on RP850/1/2/3

continuity ok on DP800 to RP831 and RP831 to chip.

 

[2informaticos]

Check BKLT_SD level; should be 0V.

 

[Dave35]

Nop, high, 11v8 and of course the QP800 stay close

 

[2informaticos]

Tried SMC reset?
Just in case, see if DFU revive helps.