820-2533 Macbook Pro - SYS_ONEWIRE: 0

[senakahks]

15 inch macbook pro charger bulb doesn't come on. Seems there is a problem with SMC. The measured voltages given below. What could be the issue and and how can I go ahead?

PPBUS_G3H: 12.6
PP3V42_G3H: 3.4
SMC_BC_ACOK: 3.2
PP1V2_S5_SMC_VDD
SMC_RESERT_L: 3.3
SYS_ONEWIRE: 0
SMC_PM_G2_EN: 3.4
PP5V_S3:0

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

SMC should be ok.
Try another Magsafe and DC-in board.
Check voltages on U6900 and U6901.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

SMC_BC_ACOK_VCC is 3.3V

So U6901 is giving the proper output.
U6900 getting the 3.3V to VCC pin. R6929 is not open.
Magsafe is woking fine with another computer

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

What about voltage on pins 4 and 5 of U6900?
And resistance to ground on pin 4 and 5?

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

U6900
Pin4 = 0V
pin5 = 0V

Resistance to ground
Pin4 = 123 Ohms
Pin5 = 1.7 M Ohms

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Remove U6900 and check voltage and resistance to ground on pin 4 again.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Pin 4 pad
Voltage 3.4V
resistance to ground 5.4 M Ohms

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Seems like U6900 was bad, replace with a new one (or from donor board).

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Great support. Thank you!

So, even multimeter is not beeping, a resistance ~ 100 ohms via a chip to ground can be considered as a short to ground. Isn't it?

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Yes, in fact continuity mode with beep will often be misleading. It really depends on the line you are measuring. On CPU VCore power rail you'd have like 6 ohms and it'd beep but that's normal. On a data line you often expect at least a kiloohm.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Valuable information. After replacing U6900, now green bulb works on charger. Fan is not working yet. Have to check now.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Now SYS_ONEWIRE: 2.8V
Green Light is ON
S3 rails are not active yet.

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

You have to trigger power button for this machine to turn on.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Tried to trigger by touching the ground to SMC_ONOFF_L. Fan doesn't move at all.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Some voltages may be useful:
PM_PWRBTN_L: 3.4V
SMC_ONOFF_L: 3.4V
PM_SLP_S4_L: 0V

When trigger SMC_ONOFF_L, PM_PWRBTN_L goes down and come up.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

The charger I have used is a 15V one. So, once charger is changed, SYS_ONEWIRE gives 3.3V
Still no luck with FAN

[piernov]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

You must use a good 85W Magsafe.

[senakahks]

Re: 820-2533 Macbook Pro - SYS_ONEWIRE: 0

Yes. That is what I am using now.
What can I check for missing PM_SLP_S4_L?