820-3330B A1286 Display but No İmage

[Tillie14]

MacBook is starting but I get a grey screen ( looking at the back, apple logo i have a backlight) but no image
I have done a lot of measurements
This is what I find very strange
U9270: pins 5 & 6. = 1.08v voltage at the same time (lcd plugged in)
U9270 replaced but no difference

U9600) is still in place? (also replaced but no difference)

voltages:
LCD_PWR_EN= 2.3v (but getting a backlight)
GMUX_S3_PD_GND= 3.0v
LCD_BKLT_EN= 3.3V
LCD_BKLT_PWM= 3.3V
LVDS_DDC_SEL_EG= 1.05v
LVDS_DDC_SEL_IG=1.05V
DP_MUX_SEL_EG=1.05v
DP_MUX_EN=3.3v
EG_RESET_L=3.3v

some suggestions or options to do?

 

[2informaticos]

Did you try known good screen assembly?
Also test external video.

 

[Tillie14]

Did you try known good screen assembly?
Also test external video.

I have only screen assembly from a 820-2915 boards Which not seems to fit.

Does the external screen test means to just plug-in an external screen to the thunderbolt connection and then an image should appear.
Then do this external screen test with a working Macbook and then I see that external screen is only activated when a hard drive with OS is installed.

Or does this external screen test is performed in another way?

Because in both case I don't see anything.

 

[2informaticos]

A1286 2011-2012 LCD assemblies are fully compatible, but the connector is slightly different; need to force it carefully.

External video may appear only if GPU wasn't disabled.

If you don't get image internal/external (w/ GPU enabled), then may have GPU problems.
Test internal image disableing GPU...

 

[Tillie14]

A1286 2011-2012 LCD assemblies are fully compatible, but the connector is slightly different; need to force it carefully.

External video may appear only if GPU wasn't disabled.

If you don't get image internal/external (w/ GPU enabled), then may have GPU problems.
Test internal image disableing GPU...

ok i will, letyou know!

 

[2informaticos]

Please, maintain forum aesthetic.
Do not quote again an entire post, visible few centimeters above...

 

[Tillie14]

I have searched the forum for disabling the GPU, but I cannot find anything about this board 820-3330.
This U8900 ISL ISL6263C is very different than from 820-2915 board U8900 ISL62882C.
Which State that removing this resistors R8910/11, but on this board they point to other contacts to the ISL .

I don't know which resistor or what to do to disable the GPU
Can you tell me, or is ther a link in this forum wich i have missed?

 

[2informaticos]

Didn't read this yet?

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

boards.rossmanngroup.com

The corresponding resistors are R8900/01 in this case.

Don't forget, external video is lost, disabling GPU...