820-01041 NO BACKLIGHT NEED HELP MISSING 60v

[alfredposadas09]

820-01041 i manage to repair the leak capacitor in C846x now the diode reading is ok i think u8400 is not working
F8400=12.56v
R8400= 12.56v
PPVOUT_S0_LCDBKLT= 1.1diode reading= 0v
PP5V_G3S_BKLT_A=5v
PP5V_G3S_BKLT_D=5v
EDP_BKLT_EN=0v <<suspicious
ISNS_LCDBKLT_P= 3.3v
ISNS_LCDBKLT_N=3.3v
I2C_BKLT_SCL=i didnt check it yet
I2C_BKLT_SDA=i didnt check it yet

[mon2]

PPVOUT_S0_LCDBKLT= 1.1diode reading= 0v

Diode reading implies a short circuit on this rail. Switch to resistance mode on your meter. Check the resistance to ground of this same PPVOUT_S0_LCDBKLT rail. Post the measurement.

[alfredposadas09]

Diode reading implies a short circuit on this rail. Switch to resistance mode on your meter. Check the resistance to ground of this same PPVOUT_S0_LCDBKLT rail. Post the measurement.

DIODE READING =0.1v before when i remove the leak caps it goes 1.1v based on flexbv5 software the reading is 1.1v diode i guess (red probe on ground and black probe on that rail)

[alfredposadas09]

does macbook lcd needs 12v to the lcd to communicate to the pch?

[alfredposadas09]

i sucessfully remove the leaked caps here in PPVOUT_S0_LCDBKLT but still no 12v

[alfredposadas09]

i sucessfully remove the leaked caps here in PPVOUT_S0_LCDBKLT but still no 12v

PPVIN_S0SW_LCDBKLT_FET=12v
LCDBKLT_EN_L=12v
voltage divider doesnt work as well u8400

[mon2]

U8400 (backlight ic) may be defective. If available, replace with a known good controller.

[alfredposadas09]

U8400 (backlight ic) may be defective. If available, replace with a known good controller.

ok sir i forgot to tell that the camera connector is blown .. ok tommorow i will replace backlight ic and give u update sir thank you so much for ur help i really appreciate it

[alfredposadas09]

i replace backlightd driver still not working

[mon2]

Review this page:

https://logi.wiki/index.php/Backlight_Troubleshooting

[mon2]

Do you have caps key led toggle?

Do you have graphics if viewed with a phone torch light on the front of the lcd? Logic board works with external display?

check the smbus lines from the camera connector. They maybe impacting other smbus slave devices/sensors.

Open lid sensor voltage to ground is ok?

[alfredposadas09]

Do you have caps key led toggle?

Do you have graphics if viewed with a phone torch light on the front of the lcd? Logic board works with external display?

check the smbus lines from the camera connector. They maybe impacting other smbus slave devices/sensors.

Open lid sensor voltage to ground is ok?

i have key caps toggled .. we hear the chime sound too

[mon2]

Check the voltage to ground of the i2c lines used by this backlight IC.

Each of the return backlight led lines must reach the backlight IC from the lcd connector.

If the lcd is not detected, the backlight will not enable.

If the lid is considered to be closed using the trackpad sensor, the backlight will disable.

Does this keyboard feature a backlight? Does it function?

[mon2]

Adding to the list...remove all power. Meter in DIODE mode. Red meter probe, yes RED to ground.

Black meter probe to point to test.

Measure the following points of interest in this DIODE mode:

I2C_DISP_SCL
I2C_DISP_SDA

Post each measurement. The above I2C / SMBUS lines are used to configure the graphics MUX (multiplexer) @ U9801. If these lines are defective or not working correctly then the LCD display will not be powered, backlight will not be enabled.

[alfredposadas09]

Adding to the list...remove all power. Meter in DIODE mode. Red meter probe, yes RED to ground.

Black meter probe to point to test.

Measure the following points of interest in this DIODE mode:

I2C_DISP_SCL
I2C_DISP_SDA

Post each measurement. The above I2C / SMBUS lines are used to configure the graphics MUX (multiplexer) @ U9801. If these lines are defective or not working correctly then the LCD display will not be powered, backlight will not be enabled.

sir this is the result upon checking

DIODE MODE:
I2C_DISP_SCL =0.422
I2C_DISP_SDA =0.422
VOLTAGE MODE:

I2C_DISP_SCL= 1.2V << is this normal?
I2C_DISP_SDA= 1.2V << is this normal?
PP3V3_S5_GPIOX_R=3.3v
PP1V8_S5_GPIOX_R=1.799v

[alfredposadas09]

hello anyone?

[mon2]

No, the parked I2C_DISP_SCL / I2C_DISP_SDA voltage is not normal. It is a good find.

Carefully review the voltage to ground of PP5V_G3S. This is the pull-up voltage rail used by this I2C pair of communication lines.

Carefully, measure that you have a valid 5 volt reading on each side of R8444 and also R8445. This power rail is used to power the backlight IC and other parts of the logic board.

Next, remove all power -> meter in resistance mode (not diode mode) ->measure the resistance to ground of PP5V_G3S. If there is a shorted part on this rail, the voltage will be lower than expected.

This power rail is created by U7650 buck regulator. This regulator may be defective or have a shorted part on the output. Measure the resistance (not diode mode) to ground @ L7600 (either side is ok).

Post each measurement.

[alfredposadas09]

No, the parked I2C_DISP_SCL / I2C_DISP_SDA voltage is not normal. It is a good find.

Carefully review the voltage to ground of PP5V_G3S. This is the pull-up voltage rail used by this I2C pair of communication lines.

Carefully, measure that you have a valid 5 volt reading on each side of R8444 and also R8445. This power rail is used to power the backlight IC and other parts of the logic board.

Next, remove all power -> meter in resistance mode (not diode mode) ->measure the resistance to ground of PP5V_G3S. If there is a shorted part on this rail, the voltage will be lower than expected.

This power rail is created by U7650 buck regulator. This regulator may be defective or have a shorted part on the output. Measure the resistance (not diode mode) to ground @ L7600 (either side is ok).

Post each measurement.

R8444\R8445=5v each side
L7600=3.3k ohm

[mon2]

Go back to the i2c lines and measure their voltage to ground on each side of the pull up resistors.

I2C_DISP_SCL
I2C_DISP_SDA

[alfredposadas09]

R5215 = PP1.8V_S5 = 1.8V /I2C_DISP_SDA=1.8V
R5216=PP1.8V_S5 = 1.8V /I2C_DISP_SCL=1.8V