820-02020 not drawing 20V stuck at 5v

Soji

Member
Macbook came in as dead, did a physical inspection on the board, found a hairline crack on the u5200, replaced it. No PPBUS short. Board is not drawing 20V. Your input will be highly appreciated.
 

Soji

Member
This is a surprise, pls, enlighten me, how can a board that is only able to draw 5V have 12V on it??
 

2informaticos

Administrator
Staff member
Since 2015/6, MacBook boards have buck-boost converter on input.
Didn't think why there are 2 MOSFET pairs (Q5230/40, before and after L5230)?

3V8_AON present?
Check some PMU LDOs.

Did you try DFU?
 

Soji

Member
3V8_AON is present
Pls can you specify the PMU and LDOs
It didn't enter DFU
But I did check some coils at the U8100
L8100 that should be 1.06V was 0.7V
L8110 no voltage present
L8280 that should be 0.94V has 0.7V
All other coils voltage are present
 

2informaticos

Administrator
Staff member
Be sure to check ALWAYS voltage on the output pin of the coils; where the filter cap is placed.

PMU LDOs on page 28 & 33.
 

Soji

Member
U7700
L77D0 has 1.2V present
L7740 has 1.06V present
L77C0 has 0.8V present
C7700/C7701 has 3.8V present
C780D has 0.78V present
C7805 has 1.2V present
L800 has 3.8V present on pin 1 and 5V present on pin 2
C7825 has 5V present
U8100
L8230 has a pulsing Voltage
L84E0 no voltage
L8290 pulsing
C81F3 3.8V present
L8281 pulsing
L8280 pulsing
 

Soji

Member
L800 has 3.8V present on pin 1 and 5V present on pin 2
R8422 no voltage present, there pulsing signal there
 

2informaticos

Administrator
Staff member
L7800 MUST have 3.8V on pin 2; comes from 3V8_AON.
If you get 5V at C7800, is OK.

Check for short on all big coils.
Also check at small coils near U7700 and U8100; especially the ones without voltage pulse.
 

Soji

Member
L7800/2 is connected to C7800/1 and it has 5V on it. L7800/1 has 3.8V on it.
I've checked all coils around U7700 and U8100, they are not shorted.
 

2informaticos

Administrator
Staff member
Do you still have pulsing L82xx coils?
You've said 0.7V on L8280 before; supposedly not pulsing.

BTW, always check DC voltage on the coils output pin, where the filter caps are placed.
 
Top