820-00850 - 5v - 0,25a

Palhano

Member
I always get this model board with this problem.

It had oxidation near UB300, with a short on the PP3V3_UPC_TA_LDO (CB308) line. I ended up with the short and the UB300 pulled 5v - 0a, the others 5v - 0.25a. So I replaced the UB300, now all ports pull 5v - 0.25a.

Voltages and measurements in diode mode on the CD3215 are OK.

I have voltages on AWAKE and SLPS2R on the U7800.

I don't have a short or voltage on the SSD and G3S lines.

It goes into DFU mode, but gives an error when restoring.
DFU state to DFU state.
[com.apple.MobileDevice.MobileRestore -
OxFCA (4042)]

Any tips?
 

2informaticos

Administrator
Staff member
Did you try DFU with good battery connected?

To avoid any problem on later steps of power sequence, try DFU with 3V3_S5 tied to ground.
If can't be completed in normal way...
 

Palhano

Member
I did the DFU with the Mac battery. I'll try with another battery.

Is it possible to enter DFU with the logic board outside the topcase?
 

Palhano

Member
I placed the logic board in a topcase with a good battery, it turns on, but does not charge the battery. It pulls 20v, but pulls 0.002a.

The DFU restore attempt did not erase the Mac. So the system starts normally.

U7000 Basic Voltages
P_IN - 5.2v
AUX_DET - 1v
SMC_RST_IN - 0
VDDA - 5v
VDDP - 5v
EN_MVR - 5v
SMC_RST* - 0
AMON -0
BMON - 0

PPBus - 12.2v
 

Palhano

Member
I'm still trying to repair it.

UPC_I2C_INT_L - 0v
CHGR_RST_IN - 0v
I checked R/C/Q7030/40

Is it worth replacing the u7000?
 

2informaticos

Administrator
Staff member
"UPC_I2C_INT_L - 0v"
USB-C ports can't switch to 20V with this signal active.
Changing U7000 will not help in this case.
 

Palhano

Member
I don't have a recorder for this chip.

But I found something strange. I don't have 1.8v on the CB302, but I do have it on the CB402. The CB302 line doesn't have any 1.8v line. I made a jumper between these components, but nothing changed.
 
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