820-3330-B No image - No Backlight.

[maxmark]

Re: 820-3330-B No image - No Backlight.

hi @maxmark.

First check that your display is working by using a flashlight on the display to confirm that you can see the graphics. If your display permits, use the flashlight on the back of the display where you can see the Apple logo. If the lid is solid, apply the flashlight around the front side edges. The flashlight will mimic the missing backlight.

Do you see the desktop, etc. graphics ?

Aside from the missing backlight, this laptop works normally ?

Do consider to apply the PRAM reset on your unit as well.

https://setapp.com/how-to/reset-pram...and-smc-on-mac

Thanks for your reply！Yes,I did,but Still doesn't work. no display,but have CHIME sound. VRAM 0V，maybe GPU die

[mon2]

Re: 820-3330-B No image - No Backlight.

hi @maxmark.

First check that your display is working by using a flashlight on the display to confirm that you can see the graphics. If your display permits, use the flashlight on the back of the display where you can see the Apple logo. If the lid is solid, apply the flashlight around the front side edges. The flashlight will mimic the missing backlight.

Do you see the desktop, etc. graphics ?

Aside from the missing backlight, this laptop works normally ?

Do consider to apply the PRAM reset on your unit as well.

https://setapp.com/how-to/reset-pram...and-smc-on-mac

[maxmark]

Re: 820-3330-B No image - No Backlight.

Hey there, I have the same board with the same issue and have a question about U8900. All of the correct voltages and enables are present for the chip but there is no output on pin 1 (pwrgood). I have replaced the chip and still same result. Any suggestions or direction on this matter would be greatly appreciated. Thank you!!

hey guys! I have the same question too! you replaced U8900 or U8000(GPU)?
Did you fix your computer at last? Any suggestions or direction on this matter would be greatly appreciated. Thank you!!

[piernov]

Re: 820-3330-B No image - No Backlight.

You should list your voltage measurements. Also, always start with history of the machine, symptoms and visual inspection.

[bdawg]

Re: 820-3330-B No image - No Backlight.

Hey there, I have the same board with the same issue and have a question about U8900. All of the correct voltages and enables are present for the chip but there is no output on pin 1 (pwrgood). I have replaced the chip and still same result. Any suggestions or direction on this matter would be greatly appreciated. Thank you!!

[MobileXT]

Re: 820-3330-B No image - No Backlight.

Try Reflow U9600

[xalapamac]

Re: 820-3330-B No image - No Backlight.

I'm two LCDS. I have two Macbook of the same model and change the LDCS. Both lcd works with another motherboard.

GPU: NVIDIA
S TAIWAN 1222A2
T0A506 M4P
N13P-GT-W-A2

[BadraYO]

Re: 820-3330-B No image - No Backlight.

what is the model of the gpu ?

[Conste]

Re: 820-3330-B No image - No Backlight.

Do you have a screen on external monitor?

[xalapamac]

Re: 820-3330-B No image - No Backlight.

I have two screens for that model, both of them work perfectly, and they're probe with another motherboard. PP3V3_SW_LCD = 0V

Put the microscope lamp behind the screen and I don't have a picture of folder.

Piernov, What's your recommendation?

[piernov]

Re: 820-3330-B No image - No Backlight.

As always you need image before worrying about backlight.
PP3V3_SW_LCD is a good place to start troubleshooting. Requires a known good LCD to be connected.

[xalapamac]

The Macbook turn on, I have CHIME sound, I have a normal fan spin. I have the Lcd attached to the Motherboard...

I have these readings:

F9700: 12V

Q9706:
PPBUS_S0_LCDBKLT_FUSED=12v
LCDBKLT_EN_DIV=12 V
PPBUS_SW_LCDBKLT_PWR = 0v

DDC Circuit:
u9000: LCD_BKLT_EN = 0v (I understand that you're only present when
you recognize the Lcd)

PP3V3_S5_LCD = 3.3V
PP3V3_SW_LCD = 0v

PM_ALL_GPU_PGOOD = 3.33v

I understand LCD_BKLT_EN It's generated in U9600 (PB7A).

I have these readings in U9600
PP3V3_S0_GMUX =3.3 v
PP1V2_S0_GMUX= 1.2v
PP1V8_S0_GMUX =1.8v
PP3V3_S0_GMUX = 3.3 v
PP3V3_S0_GMUX_LRC_VCCPLL = 3.3v
EG_PWRSEQ_EN = 3.3 v
GMUX_DEBUG_RESET_L = 3.3V

My questions:
-What are the voltages to be measurable to ensure that the u9600 is alive?
-am I going well in my busage sequence for the fault?
-what is your recommendation as an expert?

Thank you for your time