820-00045 s4 rails not present

ytesfay80

Member
This 12" Macbook was sent in as intermittently turning on when the charger gets plugged in. I removed the USB-C charging port and noticed one of the pins were gone so I replaced the port and it turned on fine after that. The only issue was that the keyboard and trackpad were not working so I replaced the trackpad cable and everything worked fine after that. I was able to shut down the machine and turn it on multiple times with no problems.

The last thing I did was run the apple diagnostics test and after it passed I shut it down and left the charger in for another 30 minutes before unplugging it. This morning I tried turning it on and it won't turn on with the charger plugged in and even after an SMC reset.

Here are some measurements I got. The 5v and 3v3 s5 rails are present but the s4 rails and pp3v3_sus is not present.

PPBUS_G3H - 8.6v
PPVBUS_E85 - 20v
PP3v3_G3H - 3.3v
PP3V3R3V0_AON - 3.24v
PPVRTC_G3H - 3.29v
PP5V_G3H_LDO - 5v

I tried measuring PM_SLP_S5_L but as far as I can tell it is at 0v. It was kind of hard to get correct spots to measure it because the probe points and resistors didn't look to be in the exact spot as the boardview says.
 
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JohnB8812

New member
There’s probably corrosion somewhere on the board or under a chip.I’d say ultrasonic and go from there if the history is liquid damage
 

ytesfay80

Member
The customer said there was never any liquid spilled on it. It was just an issue with the charger port but I will ultrasonic it and see if that fixes it.

Update: I ultrasonic'd the board but still have the same issue. I know the board is getting power because the white led comes on when the charger is plugged in without the battery being connected.
 
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2informaticos

Administrator
Staff member
Disconnect keyboard and see if board starts when plug in the charger.
You can also simulate power button using R5115/16 pads.
Check for any reaction at PM_SLP_SUS_L and PM_SLP_S5_L when you do that.
 

ytesfay80

Member
Yes I've been doing all of these tests with only the board and usb port plugged in(no other accessories plugged in).

I don't even get a pulse on PM_SLP_S5_L or PM_SLP_SUS_L when I plug in the charger and when I use the R5115/16 pads.
 

ytesfay80

Member
I wasn't sure what rtc signals to check so I searched rtc in the boardview and took these measurements.
PCH_RTCRST_L - 1.52v
PCH_SRTCRST_L - 3.28v
PPVRTC_G3H - 3.29v
PPVOUT_S0_PCH_DCPRTC - 1.08v

Pin 1(PPVRTC_G3H) of R1303 is 3.28v but Pin 2(PCH_RTCRST_L) shows 1.52v so I think that may be a problem. It measured 20kohms so the resistor seems fine.

I have a fluke 115 multimeter but I'm not sure how to measure khz on a chip. Is it possible to measure that with this multimeter?
 
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2informaticos

Administrator
Staff member
"PCH_RTCRST_L - 1.55v"
There resides your problem...
Check R1303 value.
If correct, remove C1303; if voltage goes high to 3V, change C1303.
If still low value, bad PCH; END.

BTW, the other two RTC signals are INTRUDER and INTVRMEN.
 

ytesfay80

Member
I removed C1303 and it went to 3v so that was the problem. I replaced C1303 and everything is working fine now.

Thanks a lot!
 
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