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A1466 820-3437-B no boot

F

flopper

Member
820-3437-b Board came with prior liquid damage few months ago, fixed at the time.
Customer came few days ago with not booting macbook air, i checked and noticed that there is no 5V S3 and 5v S0 also.
5v S5 present.

Was poking around and applied heat to SMC around 200c for diagnostic purpose. Mac started up, worked for 10-15 min, after cooling off same issue, so i decided to reball SMC, did it, macbook worked that evening, passed tests. In the morning i came and before calling customer decided to check it, and it is not coming on with same symptoms.
So i reballed SMC again thinking i did not good job on reballin. Same thing happened, worked same day, next day does not boot with same symptoms.
What could be the issue?
Many thanks in advance.
 
2informaticos

2informaticos

Administrator
Staff member
Do you get amber light and steady 3V3_S5/SUS?
Which is the exact PPBUS_G3H voltage?

Can you tell us where was the liquid spilled first time?
 
F

flopper

Member
Amber light - yes
G3H - 8.49v
3V42_G3H - 3.38v
3V3_S5 3.29v Steady
3V3_SUS - 3.29v Steady

Looks like prior liquid damage was around backlight and some caps on 3v42_G3H
 
2informaticos

2informaticos

Administrator
Staff member
Check PM_BATLOW_L, PM_PWRBTN_L, PM_RSMRST_L, PM_DSWPWRGD, PCH_DSWVRMEN.
Trigger SMC_ONOFF_L amd check for drop pulse at PM_PWRBTN_L at same time.
 
F

flopper

Member
PM_BATLOW_L 3.26v
PM_PWRBTN_L 3.35v
PM_RSMRST_L 2.98v
PM_DSW_PWRGD 3.35v
PCH_DSWVRMEN 2.46v

"Trigger SMC_ONOFF_L" never did this, can you explain? Sorry for lack of knowledge.
I have to short SMC_ONOFF_L to ground and measure voltage drop on PM_PWRBTN?
 
F

flopper

Member
PM_SLP_S0_L goes from 0.03v to 1.4v for split second
PM_SLP_S3_L from 0.00v to 0.70v
PM_SLP_S4_L goes from 3.3v to 0v
PM_SLP_S5_L stays at 3.29v
 
2informaticos

2informaticos

Administrator
Staff member
"PM_SLP_S4_L goes from 3.3v to 0v"
Should pulse high from 0V...

Looks like all pulse, then check for pulse on all big coils; S3 and S0 voltages.
 
F

flopper

Member
i double checked, was measuring wrong resistor.
PM_SLP_S4_L goes from 0v to 1.47v
I checked at L7520 - no pulse
L7630 - no pulse
 
F

flopper

Member
S4_PWR_EN goes from 0 to 1.17v

I rechecked L7630 and L7520 for pulse, found that i was failing to short R5116 first time.

L7630 goes from 0v to 0.53v
L7520 goes from 0v to in between 0.53v to 2.2v, (could be 1.2, sometimes 1.7, sometimes 0.76)
 
2informaticos

2informaticos

Administrator
Staff member
Any pulse at CPU coils?
Also check pins 7 & 3 of U1950.

Trigger SMC_ONOFF_L several times, to catch higher pulse.
An o-scope can catch peak pulse better.
 
F

flopper

Member
on L7320 highest peak is 0.32v
on L7310 highest peak is 0.31v

SYS_PWROK_R is 0v does not pulse if trigger SMC_ONOFF_L
PM_S0_PGOOD is 0v does pulse if trigger SMC_ONOFF_L from 0v to 1.38v highest
 
2informaticos

2informaticos

Administrator
Staff member
Make short between pins 5 & 6 of U1950 and check for pulse at pin 3.
Also try to start in SMC bypass mode.
 
F

flopper

Member
"Make short between pins 5 & 6 of U1950 and check for pulse at pin 3."
at pin 3 there is 0v even if i short pin 5&6.
i get constant voltage of 0.03v on Pin 2, is that ok?

Can i get info on how to do SMC bypass correctly?
I struggle to find legit source anywhere, as far as i find out yet it is done by holding the power button and inserting a magsafe cable? If yes, then nothing happens.
 
2informaticos

2informaticos

Administrator
Staff member
"at pin 3 there is 0v even if i short pin 5&6."
Check at the time you trigger SMC_ONOFF_L.

You mix the things and make dificil to follow you; we need accurated infor.
In other post you said to get pulse at pin 7/U1950.
"PM_S0_PGOOD is 0v does pulse if trigger SMC_ONOFF_L from 0v to 1.38v highest"
It cannot pulse, if pin 2 doesn't pulse too.
 
F

flopper

Member
sorry, i understood that i have to short(trigger) pin 5&6 at U1950 and then measure pin 3.
I have to solder a wire between 5&6 and trigger SMC_ONOFF_L while measuring pin 3? Correct?
 
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