820-00281 u9850 keeps shorting

[ThisIsWes:AASP]

the standard - pin 1/43 burn on j8500. Display side looks good.
Replaced u9850 and tested - nothing.
1/43 burned again and pin 3 short to ground. Removed u9850 and short gone.
Cleaned up j8500 and check for continuity between ground and 1/3 then replaced u9850 and verified short was gone. Even connected lcd cable and checked other end for short on pins 1/3.
Different disp, new lcd cable and still nothing. Now no burn but pin 3 is shorted again.

Should I replace j8500? Could something else be popping u9850? I'm running out of u9850s.

 

[ThisIsWes:AASP]

Replaced j8500 and u9850 (again) and all is good.

 

[ThisIsWes:AASP]

welp.. thought it was good but its not.
Boots to boot menu and install media. Will even install OS without any issues. but when finished and loading OS it gets to about 75% and the display cuts out. Otherwise, the mac is still on. "Built in screen reader" prompt is heard.
Boot from eternal is the same result. Safe mode work though.

What could this be?

 

[ThisIsWes:AASP]

Checked pull up/down resistors around u9800.

GFX_SELF_THROTTLE - 80k instead of 100k
DP_T_SNK1_HPD_EG - 82k instead of 100k

Removed u9800 and they stayed the same. Tested off the board and they were good.
Replaced u9800 with donor and new u9850.

Same result.

 

[2informaticos]

External video OK?
Did you try another LCD assembly?
PRAM reset done?

BTW, high value resistors measured onboard, always give lower readings as normal...

 

[ThisIsWes:AASP]

External video is good.
yes same result with different displays.
pram - no change.

I understand the values are different but on other boards I’m getting 98k-100k on these.

Seems to have something to do with how the OS manages the display? I even tried going back to Sierra as I know the processes run through the GPU in HS.
Also, tried disabling gpu with Medusa as I do on 820-2915.

 

[2informaticos]

Medusa can do that for 2914/15 only.
Put back original BIOS, or another known good file (clean ME).

Can you boot USB Windows/Linux Live?

 

[ThisIsWes:AASP]

Already put back. Will try another BIOS file.
I don’t have a bootable for those.. it does boot into installers and in safe mode so I would assume so. In safe mode the GPU is shown in system report fwiw.

 

[2informaticos]

Aaaa, it boots macOS in safe mode.

Installing fresh Windows can help you.
If finish the installation, start to install drivers and see when it crashes.

 

[ThisIsWes:AASP]

When connected to external, in system info under graphics/display the display is not recognized. In safe mode it is.
it seems the OS isn’t communicating with the display. Similar to how keys can work in boot menu but not in the OS?

if this doesn’t reveal anything I’ll try Windows.

 

[ThisIsWes:AASP]

Replaced disp connector - no change.

Any ideas why the OS isnt recognizing the display??

 

[SMMRepair]

GPU probably toast.