Apple A1466 power on issue

[Jacksoft]

Hi all,
I have a MacBook A1466 with 820-00165-A with a strange issue.
The Mac power on and runs perfectly, AST in EFI mode passes all the tests (even the full longer test), but if you leave the Mac off, and without the power adapter connected, for about two days without powering it on and using it, it will not power on anymore (battery have enough charge).
Already did an SMC reset but the issue still persist.

What could I check?

Thank you.

[mon2]

Re: Apple A1466 power on issue

Check if you have 3v42 rail with only the battery.

[Jacksoft]

Re: Apple A1466 power on issue

Yes, the 3.42 is present.
But now, don't know why, the Mac does not power on at all.

To be more precise:
If on battery, thermal camera show heat on CPU and SSD and after 3-4 seconds cools down.
If AC plugged in, thermal camera show a persistent heat on CPU and SSD but the Mac still not bootup.
No fan spin-up.

[mon2]

Re: Apple A1466 power on issue

Be sure the power adapter is the original.

Disconnect the battery and trackpad.

Connect the power adapter and measure that 3v42 rail is stable. Do you see the magsafe led light on the connector head? What is the color?

Check the ppbus_g3h voltage to ground.

Post your measurements.

[Jacksoft]

Re: Apple A1466 power on issue

PP3V42_G3H is 3.42V
PPBUS_G3H is 8.60V
MagSafe LED color is orange.
CPU and SSD are active with about 60°C and the fan is off.
EDIT: U7870 gets hot too, but voltages seems present.

[dellxps15]

Re: Apple A1466 power on issue

looks like audio capacitor shorted.

check also if 3,3 volt and 5 volt s5 state are present.

check if cpu vcore , ram, pch voltage are present.

[Jacksoft]

Re: Apple A1466 power on issue

Hi all,
SORRY for the huuuuuuge delay!
We tried to replace the U7870 from a working donor board (but with BGA problems) and still the same. We checked all the caps, removed the U8040 but still short, removed also the Q1920 and no luck. We thought the CPU was dead (we tested with just the MagSafe board connected).
Fully reassebled the Mac back and after some days... It started works again.
Now we don't understand how this is possible. We checked almost anything and seems there was no extra solder that could caouse a short.
We don't think could be a BGA issue (that could go away when you thight the screws).
There was a short and now there's not.
How could be possible? Any suggestion?

One thing: U7870 goes hot (45-50°C) when the AC plug is connected and instead of 1.5V on PIN 1 there was about 0.4V, but with voltage injection of 1.5V we read just 0.02A (that is the maximum amount, standing by the schematic, so is correct) in power off state (not normal), but nothing goes hot.

EDIT: We suspect there's something wrong in the trackpad/keyboard connector on the motherboard (a twisted pin, maybe) that causes shorts or something. We will inspect this in the next days.