Macbook A1502 820-3476-a no backlight

[mon2]

Re: Macbook A1502 820-3476-a no backlight

Yes, that is the output of this load switch. The input voltage is on pin #3. Confirm that pin # 3 voltage remains stable at all times.

Finally, confirm the voltage on pin # 2 = enable for this load switch.

What is the voltage reading here to ground ?

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

on pin 3 the voltage is stable, on pin 2 without connected display 3.3v with connected display 2.1v, in both cases for a temp of about 3-4 seconds to then return to 0v

[mon2]

Re: Macbook A1502 820-3476-a no backlight

Voltage on pin #3 also goes off after 3-4 seconds?

Is the display a known good display? Works ok on another board, if you have a spare test board?

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

on pin 3 the voltage is stable, the screen should work, nothing else to try nor other logic.
I replaced the lvds cable on the screen and am waiting for a new LVDS connector for the logic.
I recovered the LVDS cable from an A1398 screen and I'm sure it worked, maybe it's time to buy a new cable to clear my doubts...

[mon2]

Re: Macbook A1502 820-3476-a no backlight

Measure the voltage to ground of:

ISNS_LCDBKLT_P
ISNS_LCDBKLT_N

EDP_BKLT_EN (U8330)
LCD_PSR_EN (U8330)
EDP_PANEL_PWR (U8330)

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

ISNS_LCDBKLT_P 5.1v
ISNS_LCDBKLT_N 12.5v

EDP_BKLT_EN (U8330) 0v
LCD_PSR_EN (U8330) 0v
EDP_PANEL_PWR (U8330) 0v

[mon2]

Re: Macbook A1502 820-3476-a no backlight

ISNS_LCDBKLT_P 5.1v
ISNS_LCDBKLT_N 12.5v

Something is incorrect about these measurements.

Can you confirm the voltage to ground of PPBUS_G3H?

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

yes, I actually made a mistake, here are the correct measurements

PPBUS_G3H 12,5v
ISNS_LCDBKLT_P 12,5
ISNS_LCDBKLT_N 0v - diodo mode 0,80 ohm

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

sorry, i'm messing up, i realized now that i was measuring the wrong place, u5450 is not present on the logic.... here are the measurements

PPBUS_G3H 12,5v
ISNS_LCDBKLT_P 12,5
ISNS_LCDBKLT_N 12,5v

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

Something is incorrect about these measurements.

Can you confirm the voltage to ground of PPBUS_G3H?

what do you think of the measurements? do you think it makes sense to replace the LVDS connector?

[mon2]

Re: Macbook A1502 820-3476-a no backlight

do you think it makes sense to replace the LVDS connector?

No.

Carefully measure the voltage to ground of the following pins on J8300 with the LCD connected:

pin 3 I2C_BKLT_SCL
pin 4 I2C_BKLT_SDA

pin 6 SMBUS_SMC_0_S0_SCL
pin 7 SMBUS_SMC_0_S0_SDA

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

pin 3 I2C_BKLT_SCL 5.1v (for about 2 seconds 4.8v then back to stable 5.1v)
pin 4 I2C_BKLT_SDA 5.1v

pin 6 SMBUS_SMC_0_S0_SCL 0v (at pin 1 of the r5351 I have 3.3v, in diode mode at pin 2 I give a very low value practically 0 ohm)
pin 7 SMBUS_SMC_0_S0_SDA 0.4v

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

without display connected in diode mode to pin 6 SMBUS_SMC_0_S0_SCL I have a normal value, about 0.64 ohm and 3.3v, also the resistance value corresponds to 2 kohm, so the connected display certainly creates some problems

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

No.

Carefully measure the voltage to ground of the following pins on J8300 with the LCD connected:

pin 3 I2C_BKLT_SCL
pin 4 I2C_BKLT_SDA

pin 6 SMBUS_SMC_0_S0_SCL
pin 7 SMBUS_SMC_0_S0_SDA

forgive me if I bother you even on the weekend.. what do you think? it seems that when it detects the display it all goes down the drain
unfortunately I don't have other displays to try, only a 2015 but it's not good for this logic board

[mon2]

Re: Macbook A1502 820-3476-a no backlight

I am concerned if the LCD display is compatible with your logic board.

See this thread here:

https://www.badcaps.net/forum/showthread.php?p=984520

To confirm, the LCD display being tested is not the original supplied with this laptop?

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

I am concerned if the LCD display is compatible with your logic board.

See this thread here:

https://www.badcaps.net/forum/showthread.php?p=984520

To confirm, the LCD display being tested is not the original supplied with this laptop?

Tomorrow I'll ask the owner but I'm sure it's his display, I'll update you as soon as I have the exact information
thanks for your time ;-)

[sdogs]

Re: Macbook A1502 820-3476-a no backlight

I am concerned if the LCD display is compatible with your logic board.

See this thread here:

https://www.badcaps.net/forum/showthread.php?p=984520

To confirm, the LCD display being tested is not the original supplied with this laptop?

he assured me that it's his display .... at this point I'm still and I don't know whether to give up .... what do you think?

[rex98]

I solved mine backlight problem 0V in L3095 and L7710. i just guessed😂 and replaced the U7700 and Q7701 it works. try it
exact same model of yours.