820-2915 High fan speed. boot but black screen but stay illuminated after apple logo

protocold

Member
Board initially have fan spin for 1 second and stop, there is flux around the GPU so it has been worked on, removed R8911 and flashed bios with "820-2915 Ok no GPU clean ME.rar" and now it chimes and boot up.

But fan stuck at high speed, as soon as it finished with the Apple boot logo and the loading bar, it switched to a black screen (screen still illuminated but just black). If I press the power button, i can turn off the screen. Press the power button again I sometime see the login screen for less than a second and then it go black(still illuminated).

If i press option key while booting, as soon as something is shown on the screen, it turn black too(illuminated).
 
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2informaticos

Administrator
Staff member
Upload your backup BIOS and we try to disable GPU on it.
I hope you didn't do PRAM reset after flashing BIOS.
Put always EFI password to protect against accidental reset.
Flashing GMUX is faster (no need to remove board from shell) and resists to PRAM reset.
Tiresias GPUkiller is the better way, as it also adjust backlight.
 

protocold

Member
I actually just tried to rewrite the original bios AND did a nvram reset.

With R8911 removed, I should have a complete black screen but I DID NOT. I see the exact same thing as I mentioned above. white screen-> apple logo->black screen but illuminated.

I also saw Q9707 area has flux and soldering sign..

Possible messed up gmux?
 

2informaticos

Administrator
Staff member
Board boots with Intel Graphics and screen goes black when switch to GPU.
You should try disabling GPU in original BIOS...
 

protocold

Member
Ok I disabled GPU in the original bios and now I believe the problem is corrupted LVDS data line.
 
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protocold

Member
Located R9235 touching the R9237. Corrected it and now system boot up fine.

I also saw missing Q5502, I took one from donor board and replaced it.

However, I still have high fan spin... where should I look now?
 

protocold

Member
ah.. I just found out that the gmux is probably flashed.. as I did nvram reset and STILL only seeing iGPU.

That shouldnt have anything to do with this high fan spin right?

Let me try HWMonitor first.. dont have the ASD EFI..
 

protocold

Member
HWMonitor said:

Airport Proximity 129 C
Mainboard Proximity 128 C
Heatpipe Outgoing Air 128 C

Screenshot 2020-09-15 at 5.39.37 PM.png
 
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protocold

Member
disconnecting webcam didnt change anything.

But I measured the Q5502 again and it seems bad. Removed it and HWMonitor still show the same reading. I have replaced it again and the high spin fan is gone!
 
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