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A1278 820-2879: No power // no green light

S

SamMac

New member
Hey Everyone!

Got a 2010 MBP, no sign of liquid damage found.
No green light.
PP3V42 is present.
PPBUS_G3H rail is not present.

Checked resistance around each component with the PPBUS_G3H and all seem to show 0.24 Ohms (in 20K setting).
Not sure what to check next or where to go from here.

Thanks,
Sam
 
2informaticos

2informaticos

Administrator
Staff member
Post U6900/01 voltages.
Check contimuity between U6900 and pin central of magsafe connector.
Also check resistance to ground at L6995 on 200K scale.
SMC_RESET_L is OK?
 
S

SamMac

New member
U6900 - 0V all round
U6901 - pin 1 (SMC_BC_ACOK) shows 0.01V, PP3V42_G3H shows 3.40V and all other pins show 0V.

Not sure how to check continuity, SORRY!

Resistance to ground on both ends for L6995 shows around 51.0 (on 200K scale).

SMC_RESET_L seems good (all components showing 3.4V)

Thank you!
 
D

dukefawks

Administrator
ACOK is missing so that is a problem. Check R7005 and voltage there, also check R7021/22/51/52. If any of those are dead then also replace the ISL.
 
S

SamMac

New member
R7005: Pin 1 shows 16.45V (81 Ohms in 200K setting) and pin 2 fluctuates between 1.45V and 2.1V and inbetween them (84.3Ohms in 200K setting).

R7021/22: The resistance seems to keep going up or keep going down at differing times when i take measurements. (around 2M setting and just gradually goes bigger or smaller) and both shows 0.93V all round.

R7051/52: Both shows 0V all round.
R7051: Pin 1 shows 0.004 (2K setting) and Pin 2 shows 0.23 (20K setting)
R7052: Pin 1 shows 0.23 (20K setting) and Pin 2 shows 0.23 (20K setting)
 
A

aprendiz

Moderator
Replace ISL, R7005 and check resistance between pins 17/18 and 27/28 from ISL.... Post measurements results.....
 
S

SamMac

New member
Okay so ISL replaced, green light shows but fan doesn't spin and PPBUS_G3H showing 0.46V. R7005 shows 16.75V on both ends now.

Pins 17/18 flactuating alot not able to get a stabilised measurement.
Pin 27/28 also flactuating.

Should I still also replace R7005?
 
Last edited:
S

SamMac

New member
Replaced R7005, R7051 and R7052 and its giving the same issues.

PPBUS_G3H still giving different value of 0.53V.

Forgot to mention but getting 3.24V on SMC_BC_ACOK and 3.4V on SMC_BC_ACOK_VCC.

Anymore suggestions or would you like any more readings.
Thank you.
 
smiba

smiba

New member
To be sure, are you measuring these resistance values with power applied or not?

Also see dukes response above
 
S

SamMac

New member
CHGR_DCIN: The voltage is 16.75V

27/28: gives 20Ohms
17/18: gives 0 Ohms ---- i'm gonna check my R7051 again, its giving 0 Ohms and not giving 2.2 Ohms and the R7052 is giving 0 Ohms aswell.

I am measuring resistance without power applied.

Thanks, Sam
 
Gurmon

Gurmon

Member
SamMac said:
CHGR_DCIN: The voltage is 16.75V


17/18: gives 0 Ohms ---- i'm gonna check my R7051 again, its giving 0 Ohms and not giving 2.2 Ohms and the R7052 is giving 0 Ohms aswell.

Thanks, Sam
Click to expand...

Seems like corroded/broken traces to me. Inspect circuit coming out of pins 17/18
 
D

dukefawks

Administrator
How can corroded tracks cause a lower resistance?
R7052 is supposed to be 0 Ohm. R7051 is the one that causes the 2.2 Ohm reading.
 
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