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820-02016 with USB-C cycling at 5V, but sometimes settles at 20V and starts to boot

overshoot

overshoot

Member
I have that machine that came in, dead, with the trackpad clicking.
Customer mentioned that the machine switched off while being used.

Upon visual inspection, nothing appeared out of ordinary.

Plugged the board alone to USB-C and both ports would cycle at 5V, from 0.14A to 0.3A then charger reset.
It was doing that in a loop.

But then out of nowhere, the board settled at 20V, 0.06A and I saw the amperage rising as if it was booting (can't confirm though, it was not connected to a screen)
Then back at cycling at 5V.
Sometimes it goes to 20V and stays at 0.06A.

I've measured for short near the PMICs and nothing seems shorted.

Measurements:
PP3V8_AON_VDDMAIN - 3.8v
PPBUS_AON -12.26v
PPVDD_SOC_S1 - 0.663v (fluctuating slightly)
PP1V8_S2 - 1.8v
PP2V5_AWAKE_NAND - 2.58v
PP1V25_S2 - 1.2v
PP3v3_S2_UPC - 3.3v
PP5v_S2 - 5.2v
PP3v3_UPC0_LDO - 3.3v
PP3v3_UPC1_LDO - 3.3v
PP1v5_UPC0_LDO_CORE - 1.5v
PP1v5_UPC1_LDO_CORE - 1.5v

I have the funny feeling that it's NAND related...
 
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2informaticos

2informaticos

Administrator
Staff member
Test USB-C ports w/ and w/o battery connected.
Also test the board with known good battery (holding some charge).
 
overshoot

overshoot

Member
Well it did start but booted right away to the "go to apple support page for restore"
Charger gave me 20V and it was starting to charge the battery.

Then I've switched it off, unplugged charger.
After that It wouldn't start up and charger did its thing again, cycling at 5V.

After a while, it got me to 20V and charging but wouldn't power on.
Pressing the power button would reset the charger but no life.
 
overshoot

overshoot

Member
I have a donor board, same model, same NANDs configuration.
I have read conflicting theories about how to prepare the NANDs.

I have the P13 NAND programmer.

Can I just transplant the NANDs and use Configurator to wipe the content or do I have to use the P13 programmer (which doesn't seem to recognize them)?
 
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