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

C

CRC2018

Member
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 around U5200 as well as burned R5261 and R5262.

What i've done:
Removed U5200 - cleaned up all the corrosion underneath retinned the pads, reballed it and replaced it.
Replaced R5261 and R5262
Replaced C5260

Now i've got 5V and 0A current draw and nothing further. My best guess is that U5200 RAA489900A6 is dead and there's nothing I can do but replace it. The only problem? I can't find this IC anywhere other than China. Is there anything else I can/should check on this board?
 
2informaticos

2informaticos

Administrator
Staff member
What is diode mode to ground reading at PPBUS_AON?

Remove F5200 and check C5250 voltage.
If no voltage, then post U5200's basic voltages: P_IN, AUX_DET, SMC_RST_IN, VDDA/P, EN_MVR, AUX_OK, A/BMON.
 
C

CRC2018

Member
Presuming you mean c5252 - theres no voltage there with F5200 removed. Reading 0.1v

Diode mode on PPBUS_AON is 0.515, resistance to ground 10MOHm
 
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C

CRC2018

Member
P_IN = 5.2V
AUX_DET= 0v
CHGR_RST_IN = 0v
CHGR_VDDA = 0.142v
CHGR_VDDP = 0.096V
CHGR_EN_MVR = 0v
AUX_OK = 0v (unsure on this as I cannot get the probes under the shield very easily!)
CHGR_AMON =0v
CHGR_BMON = 0v
 
2informaticos

2informaticos

Administrator
Staff member
"AUX_DET= 0v"
Fix that.
Check diode mode to ground there.
Be sure R5215/6 have correct ohm values.
Also check CHGR_AUX_DET_SHORT_3V3 voltage.
 
C

CRC2018

Member
replaced R5215 which has given me 0.87v on AUX_DET now. CHGR_AUX_DET_SHORT_3V3 is 0V
Voltage at C5252 still 0v
CHGR_RST_IN = 0v
CHGR_VDDA = 0.144v
CHGR_VDDP = 0.100v
CHGR_EN_MVR = 0.001V
AUX_OK = 0v (still cant get the probes on it very easily so unsure)
CHGR_AMON = 0.001v
CHGR_BMON = 0.001v

i'm showing 15ohms to ground on CHGR_VDDA and 10ohms to ground on PP5V_CHGR_SW - that cannot be right surely

Edit - found a shorted cap on PP5V_CHGR_SW = removed this and now i've got 2.28V on CHGR_VDDA and CHGR_VDDP. Still no voltages on CHGR_EN_MVR, AUX_OK, CHGR_AMON, C5252 and CHGR_BMON though!
 
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2informaticos

2informaticos

Administrator
Staff member
Aaaah, calculating voltage divisor, AUX_DET is correct.

What is actual diode mode reading on VDDA/P (to ground)?
Check if R5275/6 need to be replaced.
 
C

CRC2018

Member
Diode mode of VDDP = 0.091 - seems a bit low to me but it's not shorted to ground totally
Diode mode of VDDA = 0.088 - also seems a bit low
R5275 and R5276 testing good. Done a bit more digging and I think the problem looks to be on VDDA given that resistance at pin 1 of R5275 151Ohms to ground, on pin 2 it's 156ohms to ground and on R5276 pin 1 it's also 156ohms to ground and pin 2 it's 158ohms to ground.
 
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