820-3437, backlight no display. Apple refurbished board

ALB-Repairs

Member
I have an 820-3437 doing some bizarre things.

Backlight no display, pulled all peripherals without change, Tested with a known good display.

It sometimes shows backlight no display, and other times, it Chimes over and over again, Each time it chimes, the chime becomes more and more distorted.

The board has the dreaded white apple sticker on it suggesting its a refurbished board, It looks like it had liquid damage at some point, but the board has definitely been cleaned.

Tried reprogrammed U6100, reflown SMC, replaced Lp8550, but its made no odds, im thinking the PCH or CPU is dead? anyone seen this fault before?
Thanks
 

2informaticos

Administrator
Staff member
"It sometimes shows backlight no display"
I don't exactly understand that.
Do you get sometime image without backlight?
The rest of time nothing?

Repeated chimes shouldn't be related with display issues.
There should be something affecting PCH/CPU.
Remove J6100 and inspect all SPI Bus Series Termination resistors.
Put quality flux and heat CPU untill 180-200 degrees...
 

ALB-Repairs

Member
Backlight with no image.
J6100 is okay, so are the termination resistors.

The rest of the time, it Posts with the apple chime noise, And then chimes again but slightly more distorted, and then again, and again.

Repeated chimes can be due to Display or GPU initialisation in my experience.
 

2informaticos

Administrator
Staff member
There is no dedicated GPU and it should start normal without LCD connected.
As the board has only iGPU, CPU is first suspect anyway...
 

ALB-Repairs

Member
I know that, I was just stating that it can cause similar issues.

Anyway, I was using the wifi card to test wifi on another unit and it started doing the same thing. Its the wifi card surprisingly. Close thread.
 
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