[SOLVED] 820-3115 No power on, no fan spin.

iClub

Member
Good morning, i have a mac that is not turning on. I also noticed that the charger LED is flickering on the brightness (I tested more than 1 charger).
I performed the following measurements:

PPBUS_G3H: 12.55V
PP3V42_G3H: 3.48V
PPBUS_S5_HS_COMPUTING_ISNS: 12.55V
PPBUS_S5_HS_OTHER_ISNS: 12.55V
PPVRTC_G3H: 3.4V
PP5V_SUS: 0V ~ 1.8V (PULSING)
P5VSUS_SS: 0V ~ 4.5V (PULSING)
PP5V_S3: 0V
PP5V_S0: 0V
PP3V3_S5: 0V ~ 3V (PULSING)
PP3V3_SUS: 0V
PP1V8_S0: 0V
PP1V5_S0: 0V
PP3V3_S0: 0V

Should I measure something else? Thank you.
 

2informaticos

Administrator
Staff member
Check diode mode to ground at all big coils.
If no short at L7260, remove Q7221 and check if get steady voltage at L7220/60.
 

iClub

Member
Inverse diode values on big coils:

L7260: 0V (shorted to ground in continuity mode)
L7220: 0,153V
L7330: 0,153V
L7550: 0V (shorted to ground in continuity mode)
L7510: 0V (shorted to ground in continuity mode)
L7520: 0V (shorted to ground in continuity mode)
L7100: 0V (shorted to ground in continuity mode)
L7630: 0V (shorted to ground in continuity mode)
L7030: 0,458V
L7760: 0,162V
L3895: 0,530V
L7770: 0,347V
L7700: 0,308V
 

2informaticos

Administrator
Staff member
I can't believe to have all these coils with short to ground.
Switch to ohm scale for very low values.

CPU coils have 001-003 ohm as normal for i7-i5 Ivy Bridge CPU; so pretty sure no short at L7510/20/50.

"L7260: 0V (shorted to ground in continuity mode)"
This is your problem.
You should be able to find the culprit with voltage injection method.
 

iClub

Member
"CPU coils have 001-003 ohm as normal for i7-i5 Ivy Bridge CPU"
Noted, thank you!

Using the voltage injection method, I found C6213 shorted, replaced it and the short was resolved. 5V and 3V voltages are now stable.
The board now rotates the fan, but has no logical activity.

PPVCORE_S0_CPU: 1.1V stucked (Should decrease after a few seconds, correct?)

I also tested other RAM memories, same story. Even without memory, it did not have the characteristic BIP.
What should I do now? Thanks so far.
 
Top