820-01521-02 - 5V 0.43A - No liquid damage - U7800 warms up

[it-solve]

Tried DFU mode but did not get picked up.

Under IR U7800 seems to warm up to 34*C


No visible shorts on coils, low impedance on
P0V9SLPDDR_SW0 - 53Ohm
P0V9SLPDDR_SW1 - 53Ohm

While
P1V1SLPS2R_SW0 - 8.9kOhm
P1V1SLPS2R_SW1 - 11kOhm

Lifted up L7186/Lt187 low impedance seems to be on the PP0V9_SLPDDR side. Is that normal?

Where else shall I look?

 

[2informaticos]

Do you get correct voltage at L8100?

 

[it-solve]

P0V9SLPDDR_SW0 - 1.56V
P0V9SLPDDR_SW1 - 1.55V
PWDDCPUAWAKE_SW1/3 - 0.75V
others fine


Only these I am not getting on U8100 coils
CPUCore - 0V
P1VPRIM - 0V
P0V9SSD_SW0 - 0V
P1V8SSD_SW0 - 0V

All on the right side of u8100

 

[2informaticos]

I don't know which schematic are you looking.
In the picture appears U7800...

 

[it-solve]

Apologies. Yes, it is U7800, working on 2 macs at the same time does your brain.

Corrected

 

[2informaticos]

Don't check for DC voltage at "SW" side of a coil.
Always test the output pin (DC side), where the filter cap is placed.
If you use an o-scope, will probably understand the difference.

Check if all AWAKE and SLPS2R voltages are present.

 

[it-solve]

So we should measure after the coil on outputs, rather than on the output pin side instead?




PP1V8_SLPS2R - 1.8V
PP1V1_SLPS2R - 1.1V
PP0V8_SLPS2R - 0V
Let me know if I missed any


P0V9SSD_SW0 and PP0V9_SLPDDR seem to get 1.6V now. After I unsoldered and soldered back L7816/7 not sure if related. Isn't 1.6V a bit too high for a 0.9V line?

 

[2informaticos]

I said do NOT check DC voltage on "SW" side of coil.
What is L7823 pin 1 voltage and pin2 of L7816/17?
These are the output pins for mentioned coils.

"PP0V8_SLPS2R - 0V"
This is a "good" reason for non working board.
Check diode mode to ground there.

Also check AWAKE voltages from the same page.

 

[it-solve]

Roger that. Strange that all test points are placed there. Must be for o-scope.

L7823 - 0V - 0.373
L7816/17 - 1.57V

PP0V8_SLPS2R - 0.79V - 0.2389 - I must have mismeasured it.

PPVDDCPU_AWAKE - 0.75V
PPVDDCPUSRAM_AWAKE - 0.80V
PP1V8_AWAKE - 1.8V


All the remaining reported voltages are the same.

 

[it-solve]

Just got functioning A1932 and referenced core diode mode readings on these 0V lines

PVCC_PRIM_CORE - 0.074 - 0.308 on a functioning board
PP1V_PRIM - 0.092 - 0.26
PP0V9_SSD - 0.064 - 0.276

Blown CPU / SSD? Not much dusty, used for high school classes mainly.

 

[2informaticos]

You can try changing U7800.

Once you've got working board on hands, write down diode mode readings on all coils, including the big ones.
This way build a boards library, which will save you time in the future.

 

[it-solve]

Haven't replaced one of these 338S00267 -A0's before. Seems like Stencils and chips are available. Has anyone had success in replacing these?

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[it-solve]

Just for confirmation, I have lifted up all coils on these lines and seems like short is not on the side of the PMIC



PPVCC_PRIM_CORE - 0.0169
PP1V_PRIM - 0.0254
PP0V9_SSD - 0.35

Could that PMIC is fine unless PVCC_PRIM_CORE, inputs of it are blown (AE/F 18/19)?

 

[2informaticos]

Bad news, T2 gets in the suspect position then...

 

[it-solve]

bugger.

I saw some of them on sale with a touch id. Is touch ID serialized with the board? Can't it be reused?

 

[2informaticos]

Touch ID is married with the board.

 

[it-solve]

Any known ways of reprogramming it?

 

[2informaticos]

Apple can do it...