820-3330 - No imaged or backlight on display

[macRepairAmb]

Have this board (820-3330) that came in with no image or backlight on the display. LCD_BKLT_EN and LCD_PWR_EN both reading 0volts.
i've confirmed its not the display. I also replaced the lvds connector.

PPBUS_S0_LCDBKLT_FUSED - 12.4

Any suggestions?

 

[2informaticos]

Do you get external image?
Also check for USB activity.

 

[macRepairAmb]

No external image and yes, i have usb activity. Could this be the graphics mux U9600?

 

[2informaticos]

Missing external and internal image, as backlight too, points to GPU.

"i have usb activity"
Flashing Link LED of OSX pendrive?

 

[macRepairAmb]

USB activity: Basically pulsing LED.
The frame boots up with keyboard backlight coming on around the time the OS should be fully loaded.

So if it is the GPU, that would mean the main GPU is what is bad, correct, and so bypassing the second GPU (higher graphic GPU) won't solve this issue?

 

[2informaticos]

There is a hardware method to disable GPU on this board.
I never tried it yet.
I suppose Google can find something...

BTW, once keyboard is already connected, check if Caps Lock reacts too; at least when its backlight comes on.

 

[macRepairAmb]

I've used the hardware mode and basically disables the AMD GPU. But each time I did use the mode, I was always able to initially boot into safe mode before the mode was applied. This time around, i can't even get into safe mode.

No, the caps lock isn't responding.
I'm however able to insert and eject a cd

 

[2informaticos]

If no USB activity, you have other problem, apart of video.

 

[macRepairAmb]

Did you mean if I didn?t have cap lock? Cause I do have usb activity.

 

[2informaticos]

How did you check USB activity?

 

[macRepairAmb]

Connected an external hdd and the drive had activity, granted no real way to tell if it was transmitting data, just the sound of the drive motors and the led flashing to signify comm activity.

 

[2informaticos]

Looks like USB activity confirmed.

Do PRAM reset and try again to disable GPU...

 

[macRepairAmb]

There appears to be other issues with the board that may be linked. I can't perform PRAM reset, as in the board is not responding to the key commands. I am however able to perform the SMC reset.

 

[2informaticos]

SMC reset is hardware, not software.
Did you try connecting USB keyboard on each port?

 

[macRepairAmb]

With USB keyboard it worked. It appears i've got corroded via's. This may very well be the same issue that's causing my video issue, corrosion. Looking deeper into the board, it appears the previous owner or shop had performed corrosion cleaning of the board. I'm thinking i'm done with this board.