820-3437-B

Anterweb

Member
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?
 

2informaticos

Administrator
Staff member
Did you test with original 45/60W Magsafe 2 charger?
What is exact PPBUS_G3H voltage, without battery connected?

Check resistance between pins 17/18 and 27/28 of U7100.
Also check SMC_DCIN_VSENSE/ISENSE.
 

Anterweb

Member
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,
 
Last edited:

2informaticos

Administrator
Staff member
Check R7121/22 and fix pins 27/28 problem.
You should get 2-3 ohm between 17/18, so check R7151/52 too.
 

Anterweb

Member
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?
 

Anterweb

Member
Take my time is such good advice!,

Trying to juggle jobs in between the Mrs and a 4yr old running round the place wanting to put his toy cars under my scope!

Drink in hand and a lot more relaxed I find,,,

R7121 = .245 k
R7122 = 138.7 Ohm

R7151 = 8.8 Ohm
R71572 = 0.00

Change R71572 ?

( P.s Thanks for the reminder that this game requires patience!, )
 

2informaticos

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

Anterweb

Member
Today using a donor board I replaced the following and now have these readings

R7121 = 10.0 Ohm
R7122 = 10.0 Ohm
R7151 = 2.2 Ohm

My god how fkin small are these things!

Same problem still here, will boot in SMC Bypass but just fan spin fan stop etc when powering on.

( Gutted TBH after all that resistor surgery I was convinced this would sort it )

Now getting
resistance between pins 17-18 =00.2 ohm ( Could this be a dodgy c7150?)
between pins 27/28 =20.5 ohm
 

Anterweb

Member
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
 

2informaticos

Administrator
Staff member
Check again R7151/52 and traces.
Try to get 2-3 ohm there.
It should work even with 16, but is better to get correct value...
 

Anterweb

Member
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?
 
Last edited:

2informaticos

Administrator
Staff member
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

Member
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
 
Last edited:

2informaticos

Administrator
Staff member
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

Member
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
 

Anterweb

Member
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,
 

2informaticos

Administrator
Staff member
1.44V looks good.
I posted 2.1V for 12.6V as reference; correct PPBUS_G3H is 8.5V in this case, sorry.

Try changing U7100, just in case.
Do you get correct resistance between pins 17/18 now?
 
Top