820-00185 - Macbook Air - powering on issues

LCDR2

Member
Hello

Fun little one I belive will be an easy fix!

Here's what it does

- Power button doesn't turn machine on, but will allow us to turn off. (therefore not keyboard)
- Computer will run on battery power alone, but not turn on when only battery is connected
- Computer will auto power on when connected to DC charger and functions normally, however will auto power back on when shut down.

My "Guess" for what is going on here is that the laptop thinks there is no battery connected.

SYS Detect L = 250mv approx, and I've changed batteries and DC in boards, plus an SMC reset.
PPVBat = 7.5v

investigating further but any tips are appreciated :)
 

2informaticos

Administrator
Staff member
Once machine is turned off with power button, can you turn it on again with power button?
Do NOT disconnect charger for this test.
Use R5115/16 pads, instead of power button.

Is the battery recognized and charging?
PRAM reset done?
 
Last edited:

LCDR2

Member
Hi

I can't turn it "on"with power button, as when it's plugged in it immediately turns back on.

Battery is recognised and charging.
 

2informaticos

Administrator
Staff member
It also restart if you turn it off via software from macOS?
Disconnect internal SSD and test with USB macOS.
Also test removing airport card.
 

LCDR2

Member
Hi

Changed keyboard (just in case) no effect
Wifi Card - no effect
Shutdown using software - remained off and couldn't turn back on until disconnected battery. Pushing power button resulted in Amp drop from 0.33 to 0.15 approx while button pressed.
 

2informaticos

Administrator
Staff member
Monitor SMC_ONOFF_L when you press power button.
Also check using R5115/16 pads, instead of power button.
 

LCDR2

Member
SMC_ONOFF_L - 3.5v normal, then 0.4v when pushed with power button.

Sorry not sure what you mean by " Check using R5115 pads" (This is where I checked what the voltage was)
 

2informaticos

Administrator
Staff member
I mentioned that in case power button doesn't work properly.

PM_PWRBTN_L drops when you trigger SMC_ONOFF_L?
Check PM_BATLOW_L and be sure all 4 RTC signals have good signal (above 2.4V).
 

LCDR2

Member
Hello,

Can you please explain how I trigger SMC_ONOFF_L ?

PM_BATLOW_L is 10mv with only battery connected.

I am not sure what an RTC signal is.
 

2informaticos

Administrator
Staff member
Inside PCH schematic you will find clearly delimited RTC block; look in all PCH/CPU pages.
There are 4 RTC signals (DC, not clock) easy to find.

PM_BATLOW_L must be tested with charger connected.

Press power button, or use R5115/16 pads instead, if you want to trigger SMC_ONOFF_L.
 

2informaticos

Administrator
Staff member
Machine turns on with charger alone (no battery)?

Check PCIE_WAKE_L level; be sure R1452 is good.
Also check AP_PCIE_DEV_WAKE and R1449.

Compare other WAKE signals with good board.
 

LCDR2

Member
yes machine turns on with no battery.

PCIE_WAKE_L 3.3v, resister tests at 9k ohms in diode mode.
AP_PCIE_DEV_WAKE 0v (please note computer is "on" does it need to be off. (remember as this is difficult) R1449 looks OK.
 
Top