MacBook Air A2337 (820-02016) — liquid damage, charger stuck in hiccup, no PP3V8_AON

[Giuliongo]

Hey,

Got a liquid damaged A2337 on the bench (board 820-02016 rev 4.0.0) and I'm hitting a wall. Looking for input before I keep tearing into it.

What's been done already: U5200 (ISL9240HI) was oxidized. Reflowed it first, didn't fix it, ended up replacing it. Q5240 was running at 70°C so I swapped it too. Replaced a few obviously dead passives in the oxidized area before any of this.

Board pulls 60 mA stable on USB-C. No battery connected.

Rails that are good:

• PPDCIN_AONSW 5.12 V
• PPVBUS_USBC0 5.13 V
• PP3V3_UPC0_LDO 3.43 V — Ace2 is alive
• PPBUS_AON 5.16 V solid
• PPCHGR_VDDA 5 V
• PPCHGR_VDDP 4.92 V

Rails that are dead: PP3V8_AON_VDDMAIN, PP5V_S2, PP3V3_S2, PP3V3_AON, PP1V8_AON — all 0 V. Iceman U5700 never starts.

What U5200 is doing:

• CHGR_VBAT 0.289 V
• CHGR_CSO_P 5.17 V
• CHGR_BGATE 5.16 V
• CHGR_AUX_OK 1.28 V (pulled up to PP1V8_AON_MPMU which is 0 V, so this reading is basically leakage, ignore it)
• CHGR_EN_MVR pulses to 0.18 V for about a second, then drops to 0
• CHGR_RST_IN 0 V, no short (3.01 MΩ to GND)

Classic hiccup pattern. Charger tries to come up, trips, retries.

Downstream of that: P3V8AON_PWR_EN is 0, which makes sense since CHGR_EN_MVR never latches high. P3V8AON_FAULT_L sits at 0.63 V because Iceman has no input.

Where I think I am:

This board is supposed to boot from USB-C without a battery. In that case U5200 should pre-charge PPVBAT_AON_CHGR_REG through its internal reg and CHGR_VBAT should come up to something usable. Mine just sits at 0.289 V, which is what's tripping the charger into hiccup.

So either:

• something is pulling the VBAT rail down (cap shorted partial, dead FET leaking, etc.)
• R5260 (5 mΩ shunt) is open
• Q5265 (BGATE FET) is dead even though gate is driven
• something on the BMU side (J5150, Q5155, D5150) is dragging the rail

Going to pull the board off USB and ohm out PPVBAT_AON_CONN to GND next, then check R5260 and Q5265.

Questions for anyone who's done a few of these:

• Anyone seen this exact behavior on a 820-02016 specifically?
• Does this board actually boot cleanly with no battery, or do you guys always plug in a battery / simulate one with a bench supply?
• Any known weak spot on the VBAT rail with liquid damage on this model? Cap that's notorious for going short, etc.

Thanks

 

[2informaticos]

Remove F5200 and check C5254 voltage.
Also check diode mode to ground at PPBUS_AON and 3V8_AON.

Post U5200's basic voltages: P_IN, AUX_DET, SMC_RST_IN, VDD/P, EN_MVR, AUX_OK, A/BMON.

 

[Giuliongo]

PPBUS_AON : 0.50V in diode mode
3V8_AON : 0.135V in diode mode

C5254 / PPVBAT_AON_CHGR_REG : 5.13V after removing F5200

I have 5V, 0.414A on my USB-C Tester after cleaning, the Q5240 is heating but when I clean it again it went back to 5V 0.06A. I already replaced it same issue.

It goes straight to 5V, 0.40A when I plug in the usb c.

PPDCIN_AON_CHGR_R : 5.05V
CHGR_AUX_DET : 1.10V not stable
CHGR_RST_IN : 0V
PPCHGR_VDDA : 5.00V
PPCHGR_VDDP : 4.96V
CHGR_EN_MVR : 0V
CHGR_AUX_OK : 0.72V-0.77V
CHGR_AMON : 0V
CHGR_BMON : 0V

Thanks for your help!

 

[2informaticos]

"3V8_AON : 0.135V in diode mode"
That may be a big problem in the system side.
Expected reading is in range of 0.350-0.450; just in case, compare with good board.
BTW, stop writing "V" for diode mode reading; avoid any confusion with voltage reading (when board is powered).

"C5254 / PPVBAT_AON_CHGR_REG : 5.13V after removing F5200"
That is a problem in the main power supply area.
Replace both Q5230/40; be sure all traces are good.
Also check/replace R/C5230/40; any broken trace no good there.

You must get 12.3V at C5254, before resolder F5200.

 

[Giuliongo]

I’ve replaced the Q5230/40 component. Now, I have a 5V output with a current of 0.01A. When the fuse is removed, the PPVBAT_AON_CHGR_REG voltage stabilizes at 3.69V. Upon visual inspection of the R/C5230/40 component, I don’t notice any signs of damage. They appear to be in good condition.

I’m unable to find the Q5230 component in my schematic to understand its function. Could you please help me locate it?

 

[2informaticos]

"I’ve replaced the Q5230/40 component"
These are TWO components; Q5230 & Q5240...
"I’m unable to find the Q5230 component in my schematic"
???

If you get any other voltage than 12.3V at C5254, replace U5200; if all components above mentioned are good.

"They appear to be in good condition"
At least the resistors can be checked in ohm scale.
I didn't ever see any EYE-meter good enough.
Capacitors can be checked with LRC tweezer; replaced, if not available.

 

[Giuliongo]

I have replaced Q5230 and Q5240 with the ones from a donor but I don’t find in schematic what’s Q5230 does.

I will replace the capacitor and resistor from a working donor. If still not working I replace the U5200.

Thanks for your help

 

[Giuliongo]

Hey,

Worth mentioning: U5200 has already been replaced during this troubleshooting (twice actually — first one didn't fix it, second one is a brand new reballed chip, current install). Soldering on U5200 visually looks OK.

R5230 and R5240 checked OK with the ohmmeter. I don't have an LCR tweezer for the caps, so I'll replace C5230/C5240 with known-good ones to be safe.

With F5200 removed and USB-C plugged in, here are the current readings:

• Total current draw: 8 mA
• PPDCIN_AONSW: 5.13 V
• PPDCIN_AON_CHGR_R / P_IN: 5.13 V
• PPCHGR_VDDA: 0 V
• PPCHGR_VDDP: 0 V
• PPBUS_AON: 0 V
• C5254 / PPVBAT_AON_CHGR_REG: 0.71 V
• CHGR_VBAT: 0 V
• CHGR_EN_MVR: 0 V
• CHGR_AUX_OK: 0.345 V
• CHGR_AUX_DET: 0.80 V

P_IN is good, but VDDA and VDDP are both at 0 V - those are generated internally by U5200 itself, so the chip is clearly not starting up at all.

Do these readings point to anything specific in your experience? Could this be a bad solder joint on U5200 (even though it looks clean visually), or do you think the chip itself is bad again?

At this point the only suspects left on the charger side seem to be U5200 itself, Q5230 and Q5240 - am I missing something else that could prevent VDDA/VDDP from coming up?

Thanks!