Macbook Air 820-00165 Not turning on

[Merc]

This is my first Macbook repair. No signs of liquid damage.

Laptop does not power on. I have a 45W Magsafe 2 charger. When I connect it, the light turns green for a second and then amber.

PPBUS_G3H = 8.6V
PP3V42_G3H = 3.42V

No 5V signals are present. There does not appear to be a short on the 5V rails. No signs of life with board out of chassis so no keyboard or other peripherals connected.

What do I check next?

[piernov]

Re: Macbook Air 820-00165 Not turning on

What's the history of the machine?
No PP5V_S5 you mean? Check SMC_PM_G2_EN.

[Merc]

Re: Macbook Air 820-00165 Not turning on

I don't know much of the machine's history. I bought it broken from eBay. The listing claimed it was working and suddenly died one day. It also said the keyboard was fully functional up until the laptop stopped working.

SMC_PM_G2_EN = 3.42V
PP5V_S5 = 5.0V

There was another 5V rail that was missing. I'll have to search for it.

Thanks piernov

[piernov]

Re: Macbook Air 820-00165 Not turning on

Check all your power rails again.
And make sure you use a *genuine* Magsafe 2 (no 1→2 adapter).

[Merc]

Re: Macbook Air 820-00165 Not turning on

Yes I believe it is genuine Magsafe 2. No adapter.

PP5V_S4RS3 = 1.15V checking on L7520. This voltage rises slowly to 1.15V after I connect the charger. Takes a couple of seconds.

[Merc]

Re: Macbook Air 820-00165 Not turning on

Here is charger.

[Merc]

Re: Macbook Air 820-00165 Not turning on

P5vs4rs3_en = 0.9v

[piernov]

Re: Macbook Air 820-00165 Not turning on

Those are weird voltage measurements… doesn't look good.
Check voltage on PM_SLP_SUS_L, PM_SLP_S5_L and PM_SLP_S4_L.

EDIT: and post a picture of the CPU area, heatsink removed.

[Merc]

Re: Macbook Air 820-00165 Not turning on

PM_SLP_SUS_L = 3.32V
PM_SLP_S5_L = 0.75V
PM_SLP_S4_L = 0.93V

Taking heatsink off of CPU...

[Merc]

Re: Macbook Air 820-00165 Not turning on

CPU area. Paste was silver and looked fresh.

[rediii]

Re: Macbook Air 820-00165 Not turning on

PM_SLP_SUS_L = 3.32V
PM_SLP_S5_L = 0.75V
PM_SLP_S4_L = 0.93V

Taking heatsink off of CPU...

sounds like a rabbit hole, inspect the board again (hope u didn't clean it), maybe u can find something really suspicious

[KvnTM]

Re: Macbook Air 820-00165 Not turning on

Resistor below the jtag connector on the bottom left looks a bit dodgy.
Also it looks like there are some missing parts on the two fets below the inductors. The whole area on the buck converters look like someone had a go on those. Looks like flux residue if you ask me.

You should verify with boardview and schematic.

[piernov]

Re: Macbook Air 820-00165 Not turning on

Yes, inspect closely for liquid damage.
Voltages on PM_SLP_S5_L and PM_SLP_S4_L are weird. I'd expect something closer to 0V if they were really missing.

Check voltage on all the _SUS rails.

[Merc]

Re: Macbook Air 820-00165 Not turning on

Pvp1v05_sus=1.05v
pvp3v3_sus=3.33v

[Merc]

Re: Macbook Air 820-00165 Not turning on

PP5V_S4RS3 = 1.14V

I suppose this points back to the PP5V_S4RS3_EN line which comes from PM_SLP_S4_L?

[piernov]

Re: Macbook Air 820-00165 Not turning on

Check voltage on PM_RSMRST_L and PM_PWRBTN_L.
Measure resistance to ground on PM_SLP_S5_L and PM_SLP_S4_L.

[Merc]

Re: Macbook Air 820-00165 Not turning on

PM_RSMRST_L = 3.3V
PM_PWRBTN_L = 3.41V
PM_SLP_S4_L = 84k to ground
PM_SLP_S5_L = 31k to ground

[Merc]

Re: Macbook Air 820-00165 Not turning on

SMC_CLK32K is present

[Merc]

Re: Macbook Air 820-00165 Not turning on

PM_PCH_SYS_PWROK= 0V
Does the PCH require this to be high before it will put out valid signals?

[Merc]

Re: Macbook Air 820-00165 Not turning on

This turned out to be C2950 shorted which also killed U8000.