A2991 820-02917 Stuck at 5V 0 Amps

[Instafixx]

Using 820-02935 Schematics as reference.

PPBUS is 12.3V
3v8_AON is 3.8V
PP1V8_AON_LPMU is at 1.8V stable
PP1vS2 Missing NO SHORTS
PP3V3_S2 Missing NO SHORTS
PP3V3_UPC0_LDO Missing NO SHORTS

PP1V2_NAND0 Missing ( DIODE TO GROUND 0.082)

Removed LN430.

Short Remains on the NAND Line.
NAND Gone ?

 

[Instafixx]

Injected 0.8V and found CN338 beside the NAND getting warm. Removed it. Short Gone. Replaced it.
Still stuck at 5V and 0 Amps.

Wont go into DFU as well.

 

[2informaticos]

Do you get all PMUs LDOs stable?
Tried again DFU?

 

[Instafixx]

No. All voltages remain the same as before.
Nothing heats up on the board as well.

How to go about it?

 

[Instafixx]

PPVDD_DISP_EXT_AWAKESW is .024 Diode to ground.
Becuase of this FPMU_BUCK1_LX0/1 are also 0.024 diode to ground.

 

[2informaticos]

Any chance to compare with good board?

 

[Instafixx]

Dont have good board !

 

[2informaticos]

Diode mode to ground at 3V8_AON?

 

[Instafixx]

I get 3.8V at 3V8_AON

 

[2informaticos]

And can't measure in diode mode?

Lower reading than expected can give you an idea...

 

[Instafixx]

its .314

 

[2informaticos]

Possibly bad U8100, if you don't get its LDOs (page 44).

 

[Instafixx]

PPVDD_DISP_EXT_AWAKESW is .024 Diode to ground.
Becuase of this FPMU_BUCK1_LX0/1 are also 0.024 diode to ground.

Removed L7810/11/12 - i figured if i can get the macbook on with No Display.
All connected to U7700.
Now no shorts connected to U7700 and my LDOs are back. Macbook stuck at 5v and drawing some amps now.

Now should i try a DFU revive and see if data is recoverable?
Or inject voltage to PPVDD_DISP_EXT_AWAKESW hoping its a capacitor and not the GPU inside the M3 chip that is bad.

 

[Instafixx]

I tried putting in DFU successfully.
DFU Revive is stuck at Step 4 or 4 "Installing System" and the bar has barely started.

Same for dfu restore

 

[Instafixx]

Even injected 1V
Draws very less AMPS and nothing heats up.

Please help.

 

[2informaticos]

You don't have pure short, nothing can heat there.
Should be good to campare diode mode reading with similar working board.