820-3437-B

[Anterweb]

Macbook looks very clean no signs of liquid damage, Im defiantly the first person to open this,

I presumed it was just a battery issue but tried it now with 3 known good batteries,

With a battery connected I get no boot no screen just fan spin up for a few seconds then stops then spins then stops and so on it goes..

If I remove the battery and turn on in SMC bypass it boots and works fine and if I shut it down from here I can turn it on again via power button and it will work fine until I remove the magsafe, the ill need to start first time in smc bypass again,

Any ideas?

 

[Anterweb]

45/60W Magsafe 2 charger? = Yes

PPBUS_G3H voltage = 8.57v

pins 17/18 = 33.6 ohm
pins 27/28 = .542k

SMC_DCIN_VSENSE = 2.73v
ISENSE _DCIN_ ISENSE = 30,0 mA - Jumps around the mA range a bit as the machine powers up the off,

 

[Anterweb]

R7121/22 both seem fine at 16. 3v on both traces and upto u7100
R7151/52 both seem fine getting 8.56v

It still boots with smc bypass but it just does the on off fan spin without,

I'm kinda stuck now don't know what to check, before having this help from you I would try reflowing Smc. Is this wise?

 

[2informaticos]

Take your time and maybe tell us exact ohm value of mentioned resistors...

 

[2informaticos]

Check values mentioned on schematic and replace damaged resistors.
Only R7152 looks really good; why to change it???

 

[Anterweb]

Removed c7150 and get 16.6ohm

I think hmm this can't be right, so put back c7150 and get 16.6!
Remove c7150 again left off board still getting 16.6 ohm

 

[Anterweb]

Gone over all of yesterday's work all resistors are good with perfect readings, all traces are good area nice and clean.

Now pins 17/18 reading 30 ohms!

I even tried replacing r7151/2, with others from a second donor board, it must be something else pulling this up?

Still get 3 seconds on 3 seconds off fan spin and only boots in smc bypass

Would it be worth try swapping U7100 with one from a donor board?

 

[2informaticos]

2.2 + 0 + 0.01 cannot be equal 30 for sure!
So you still have a problem there.

Just in case, check SMC_DCIN/BMON_ISENSE and SMC_DCIN/PBUS_VSENSE.
Do you get correct AVREF_SMC?

 

[Anterweb]

Yer I'm checking the readings on the donor boards and as you say should be 2/3 ohm, I just can't find any bad trace or bad component in that area they all test fine and look the part all traces test fine to.

Smc_dcin_isense = 30mv
Smc_bmon_isense = 60mv

Smc_dcin_vsense = 2.75v
Smc_pbus_vsense = 2.44v

AVREF_SMC is a solid 3.3v

 

[2informaticos]

Did you replace R7151/52 with correct values?

"Smc_pbus_vsense = 2.44v"
Looks too high for me; 2.1V expected.
What is exact PPBUS_G3H voltage (charger alone)?

 

[Anterweb]

R7151/52 replaced using a 820-00165-a donor board. the schematics say that these parts are identical on both boards.

PPBUS_G3H voltage = 8.57v

 

[2informaticos]

""Smc_pbus_vsense = 2.44v"
Looks too high for me; 2.1V expected."
What is actual reading?

 

[Anterweb]

1.443v

Just checked my notepad and it was reading this same value also yesterday and I must have made a typo when posting readings, sorry,