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Board A1286 mid 2012, 820-3330, no video

V

VinceLx

Member
Hello all,
This is my first post! Don't hesitate to tell me where I can improve.
So, I have a board A1286 mid 2012, 820-3330, with no video
- Green light on charger OK, I=1.85A with U=18.5V
- Fan spins OK
- Chime OK
- Backlight OK
- Grey screen also on external screen, but no image
- Mouse in USB: red light for 30 seconds, then off

Measuring - I put () for the theoretical values on the schematic:
PP3V42_G3H (3.42V): 3.41
PPBUS_G3H (12.8V): 12.6

LCD:
PP3V3_SW_LCD (3.3V): 3.3
PP3V3_S0_DDC_LCD (3.3V): 3.35
PPVOUT_S0_LCDBKLT - PPVOUT_SW_LCDBKLT (50V): 30.2 (here I don't know why I have 30V instead of 40V or 50V as indicated on the schematics)

GPU rails:
PM_ALL_GPU_PGOOD (3.3V): 3.34
PPVCORE_S0_GFX_REG / PPVCORE_GPU (1.0V): 0.91
PP1V5R1V35_GPU_REG (1.5V): 1.36
PP1V05_S0GPU_REG (1.05V): 1.06

PP3V3_S0GPU_FET (3.3V): 3.34
PP1V8_GPU_FET (1.8V): 1.84

Chipset rails:
PPVCORE_S0_CPU_REG (1.25V): 0.92
PPVCORE_S0_AXG_REG (1.05V): 0.93
PP1V5_S3_CPU_VCCDQ (1.5V): 1.5
PP1V05_S0_CPU_VCCPQE (1.05V): 1.06
PPVCCSA_S0_REG (0.9V): 0.81

All was ok here, so I tried around U9600:
PP3V3_S0_GMU_R: 3.33
PP1V2_S0: 1.2
ALL_SYS_PWRGD: 3.33
GMUX_S3_PD_EN:0
GMUX_S3_PD_GND:3.34
LCD_PWR_EN:3.33

So basically it seems that all powers are ok (except maybe for the backlight?), and I don't understand why I have no image. This can be GPU dead?
 
2informaticos

2informaticos

Administrator
Staff member
Welcome to the forum!

If no internal, nor external video, usually GPU issue.


"Mouse in USB: red light for 30 seconds, then off"
Caps lock reacts after these 30s?

Any history available?
 
V

VinceLx

Member
Thanks!
Caps lock is faint green from the moment it chimes. It never disappears, stays always with the same intensity, pressed or not.
If I press caps lock (or ESC, or space bar) several times just after the mouse switches off (the 30s), red light appears for 3-4 seconds, then no reactions. If I wait 5 seconds after switch off, no way to have a red light again.
No history on this laptop, it comes from Ebay, but I don't see any water damage
 
2informaticos

2informaticos

Administrator
Staff member
eBay boards are usually good for scrap.
I do not recommend to waste time.
However, if you have so much free time as me and others (these days) you can try known good BIOS.
 
V

VinceLx

Member
Thanks, I just want to go as far as I can, especially because I do not risk a lot with this board.
BIOS: this correspond to the "Boot ROM version", in the Hardware overview?
Is this contained in the EFI chip?
If yes I can replace the EFI chip with a good one from the exact same board reference, this would do?
I never did any BIOS flashing, so for the moment I would prefer to get a hardware fix (if any is possible)
 
2informaticos

2informaticos

Administrator
Staff member
BIOS chip (U6100) from other board will have dirty ME region for your board.
In theory, should serve as test.
ME region can be cleaned at the end.
We should also have some link for clean BIOS on the forum...
 
V

VinceLx

Member
It works!!! Swaped the BIOS chip, and here is the blinking folder!! Wooow... Thanks for the idea!!!
Now I have 2 good boards and one chip :D
About cleaning ME region: no idea about that, is it mandatory in case of new BIOS chip? If the board passes AHT, would that be ok?
Otherwise I made some searches, it seems to exist simple ways, like here, with the possibility to get EFI firmware from Apple installation disk:
https://github.com/corna/me_cleaner/issues/230
or other much complex (for me), here:
https://ghostlyhaks.com/blog/apple-efi/25-clean-me-region
or this one that would require me one year study...
https://www.win-raid.com/t1658f39-G...-CS-TXE-Regions-with-Data-Initialization.html
Do you recommend any trustful tutorial?
 
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