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mac book air 820-00165-a no boot

V

Vidax

New member
Hello,
I am facing an issue with a mac book air 820-00165-a mother board.
When i connect the board on power supply the current go to 100mA and immediatelyfall and stay at 30 mA.
The green and orange light is present on the charger but i don't have a fan spin.
As i have a green light G3H lines are presents.
More over i have all S5 power rails active on the board.
PPBUS_G3H = 8.55V
PP3V42_G3H = 3,41V
PP5V_S5 = 4.97V
PP3V3_S5 = 3.31V
PP3V3_SUS = 3.31V
but i don't have S4,S3 and S0 voltages.
I tested for shorts but everything seems good.

When i measure S4,S3 and S0 power rails during the boot sequence (that means when current jump to 100 mA on the power supply), I can see a jump on each lines, that means the board try to enable voltages from S4 to S0 but turn off everything immediately except for S5 power rails

Can someone help me please,
thx,
Vincent

PS: no sign of liquid damage on the board
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

You should try starting in SMC bypass mode as first step.

Trigger SMC_ONOFF_L and check every time what happen on all secondary power rails.
Do not forget pages 57/58.
Check for short, where you don't catch a pulse.
Also check for pulse at pins 7 & 3 of U1950.
VCORE pulsing too?
 
V

Vidax

New member
Hi,
bypass mode is that when you try to boot pressing ctrl+alt+shift keys ?
If thats true i already tried it
 
2informaticos

2informaticos

Administrator
Staff member
Is not that and was so many times explained on the forum; even Google has an idea about it.
Press power button, connect charger and maintain button pressed 5-10s; it should start with fan at max.
You can use R5115/16 pads, instead of power button.
 
V

Vidax

New member
Hi,
When i boot the device in smc bypass mode, the fan start spinning but stop directly
thx,
Vincent
 
V

Vidax

New member
Okay i did it but i did not found a non pulsing rail but pin 7 of u1950 is pulsing so i think that means S0 lines can all be powered on
but pin 3 is not pulsing
 
2informaticos

2informaticos

Administrator
Staff member
I suppose you don't get any pulse at pin 6, just on 5 only.
VCORE must pulse, check that (L7310/20).
If yes and still no pulse at pin 6, then try a trick: tie pins 5/6 together (solder blob) and test the board.
 
2informaticos

2informaticos

Administrator
Staff member
Try known good working BIOS, just in case.
Several links for clean ME files are already posted on the forum.
 
V

Vidax

New member
Hi I didn't test yet for BIOS issue but I came with an other good clue for debug I think.
Customer told me that the macbook was starting up by itermittence before and now don't want to boot.
 
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