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820-03286 (A2941) - No PPBUS_AON / Stuck at 5V

HeyWatchOutDude

HeyWatchOutDude

Member
Hi,

I have an 820-03286 (A2941 / MacBook Air M2 15” 2023) that has no PPBUS_AON and gets stuck at 5V / 0.05A.

Note: I replaced U5200 because PPCHGR_VDDA/VDDP was only at 4.5V. After replacing it with an ISL9240 (from a MacBook Pro M1 2020), it’s now back to 5V.

Current measurements:
  • CHGR_AUX_DET: 0.8V
  • P3V8AON_PWR_EN: missing (Diode: 0.485)
  • P3V8_AON: missing (Diode: 0.317)
  • PP5V_AON: missing (Diode: 0.494)
  • P5VS2_PWR_EN: missing (Diode: 0.485)
  • PP5V_S2: missing (Diode: 0.485)
  • PPBUS_AON: missing (Diode: 0.485)

Any suggestions on where to start troubleshooting from here?
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
PPBUS_AON MUST appear first.
It supplies all secondary power supplies, including 3V8_AON.

Any history available?
Did you check diode mode to ground at PPBUS_AON?
 
HeyWatchOutDude

HeyWatchOutDude

Member
Yeah I have added the diode value, please check again.

UT360 (Line: PP3V3_S2_HOLD_IPD) was shorted, I have replaced it - short was gone.

But now it stucks at 5V (Before it was booting fine but without keyboard/trackpad functionality)

https://imgur.com/a/PoVm85D

PPDCIN_AON_GHGR_R = 5V
R5221/5222/5261/5262 = 1ohm (Note: R5261 was at 100kohms, I have replaced it with 1ohm - still no PPBUS_AON)

Is the ISL9240 not compatible with the A2941? Before replacing it with ISL a RAA489900A6 was in use.
 
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2informaticos

2informaticos

Administrator
Staff member
Someone said ISL9240 worked instead of RAA489900A6, other people said no.

Macbook Air A2681- 820-02536 stuck at 5v after liquid damage

So got my first 820-02536 board in today for repair - customer says it just turned of by itself completely negating to tell me the full story of the liquid spilled onto it! Anyway originally when it came in I had 5V 0.3A power draw, after taking the board out I found heavy amounts of corrosion...
boards.rossmanngroup.com boards.rossmanngroup.com

Always better to use original part!
 
HeyWatchOutDude

HeyWatchOutDude

Member
I’ve already ordered two (just in case). I’ll let you know if it fixes the issue or not.

Note: I’ve tried it with a known good ISL9240 - seems like it is not compatible (at least on the A2941).
 
HeyWatchOutDude

HeyWatchOutDude

Member
Other “issue” … the right speaker is sometimes crackling at 100% volume with heavy bass, I have already tried a new speaker same behavior - any idea?

Edit: The trackpad haptic feedback is also unreliable (50/50 not working/working) I have already replaced the cable, same behavior - seems like a board issue, where to start?

PPBUS_AONSW_TPAD = 0V

Trackpad and keyboard are working. (just feedback doesnt work)

Edit2: Now it doesnt power on - Stuck again at 5V / 0.03A (PPBUS_AON = 12.27V)

I have noticed that P5VS2_EN and P5VS2_PWR_EN are not stable (0.6-1.3V / 0.650)
PP1V8_AON = 1.2-1.8V (not stable)
PP3V8_AON = 3.8V (stable)

Edit3: After measuring at PPBUS_5VS2_VIN the voltage on the usb-c meter jumped up to 20V / 0.07 - 0.40A (CPU getting warm)

PPBUS_AON = 11.96V (stable)
PP1V8_AON = 1.8V (stable)
P5VS2_EN and P5VS2_PWR_EN = 1V (stable) / 0.642
PPBUS_5VS2_VIN = 11.96V (stable)
P5VS2_PGOOD = 0.6V / 0.510
PP5V_S2 = Short
PP3V3_S2 = 3.3V (stable)
PP1V8_S2 = 1.8V (stable)
PP1V25_S2 = 1.25V (stable)

Detected via DFU mode - unable to restore. (due the missing PP5V_S2 rail)

Note: No image but I think that's due to the missing PP5V_S2 rail, right?

Edit4: Found the issue .... UC300 was shorted, I will order a new one. (P5VS2_SW was short to ground)
 

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2informaticos

2informaticos

Administrator
Staff member
"Faulty UC300?"
You already said is shorted.
Replace it and check all adjacent components and traces.
 
2informaticos

2informaticos

Administrator
Staff member
Each one has series resistors on its output; RR7x2/3, 0 ohm, 0603 in size.
Remove the pair for each chip and check if problem persists.

BTW, write directly into bottom reply box, instead of clicking Reply button.
 
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