A2337 820-02016 2020 Macbok Air Stays On 5V

Hello Everyone,

One of my customers brought me a macbook air A2337 , board number 820-02016. When I plugged it in I can see that it stays around 5.170V and amp goes up to between 0.27 and 0.388 and back to zero again. And it is on a loop like this. When I measured the
CF505 on PP1V5_UPC1_LDO_CORE = 1.5V Stable,
CF508 on PP3V3_UPC1_LDO = 3.5V Stable,
CF500 on PP3V3_S2_UPC = up and down between zero and 0.2V but it goes up partly and goes donw again partly (I mean partly every 1 second it goes down to zero then goes up 0.1 then zero and 0.11 and back same way down from 02.V)
CF402 on PP1V25_S2 = between zero and 0.5 (same as CF500)
R8441 on UPC_PMU_RESET_3V3 = around zeroV
CC337 on PP5V_S2 = 0.001V
RF235 on UPC1_5V_EN = 0.13V
RF901 on USBC1_3V3LDO_EN = 0.0V

Just because of these I thought the problem is UF500 but do I miss something else or am I right? Want to check with you guys anyway.

Thank you for you help in advance.

Emre
 

2informaticos

Administrator
Staff member
Any history fault available?
What about PPBUS_AON and 3V8_AON?

Check diode mode to ground on S2 power rails.
 
Any history fault available?
What about PPBUS_AON and 3V8_AON?

Check diode mode to ground on S2 power rails.
PPBUS_AON keeps going up and down between 7V - 12V
3V8_AON keeps going up and down between 2.9V- 3.8V
RC714 on P3V3S2_PWR_EN jumps from 0 to 0.025 on diode mode
 

2informaticos

Administrator
Staff member
Jumps in diode mode?
I hope you didn't check with power applied.

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

2informaticos

Administrator
Staff member
Check diode mode on all big coils.
Also check for any voltage spike.

Should check diode mode on master/slave PMUs rails too.
 
LC710 on P3V3S2_SW and PP3V3_S2 gives ground on both legs on diode mode
i have checked all big coils and all i found is the one written above
i have checked pmu rails seems no problem (i dont know if i did it right, i have checked them also on diode mode)
And when I measure it I can see small voltage spikes on LC710 too from 0.00V to 0.024 and back and again
 

2informaticos

Administrator
Staff member
Compare resistance to ground at LC710 with known good board.
If is pure short, something got burnt there.
 
I have sorted the problem out. First I took the LC710 our of the board and checked the legs on diode mode. And found the short line. And it was 3.3V leg. So ı took the board under thermal camera and gave 3.3V to that line and found shorted capacitor. Moved it away. Put the LC710 back measured it again and Yay no shorts anymore and back to live.
 
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