Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

[ronyan]

I have a 820-00165 board that is power pulsing twice going from drawing 34mA up to ~350mA then back down to 34. No fan spin. It is missing the PM_SLP_S4_L signal. As I have no previous experience with this particular problem, I've been measuring a lot and have already replaced U1900 and U1950. I've also replaced R5513 near the SMC that looked corroded. The behavior of the power pulsing twice has not changed.

I've watched some of Louis' youtube videos on the issue and have checked the SPI resistors for continuity and they are good, probe points are also excellent, no signs of corrosion. The board condition looked very good on first inspection under the microscope with some minor dust accumulation.

These are the signals I've measured:
PPBUS_G3H - 8.6v
PPBUS_S5_HS_OTHER_ISNS - 8.6v
PPBUS_S5_HS_COMPUTING_ISNS - 8.6v
PPDCIN_G3H_ISOL - 14.8v
PPDCIN_G3H - 14.85v
PP3v42_G3H - 3.43v
PPVRTC_G3H - 3.3v
PP5V_S5 - 5v
PP3v3_S5 - 3.3v
PP3v3_SUS - 3.3v

PP3v3_S4 - 0.025v
PM_SLP_S4_L - 0v

PM_SYSRST_L: 0.55v
PM_PCH_PWROK: 0.144v
PM_RSMRST_L: 3.286v
PM_PWRBTN_L: 3.421v
SMC_ADAPTER_EN: 3.428v
PM_BATLOW_L: 0.036v

These are the signals I've noticed that are pulsing twice and then dropping to 0v:
PP5v_S4RS3
PP5v_S4
PP5v_S0_FET_R
PP1v05_S0
PM_S0_PGOOD


I've inspected the condition of the PCH/CPU and it looks good, no cracks or defects are visible. I have measured the PPVCC_S0_CPU resistance at C1031 @ 20 Ohms.

I've thought maybe there is a short somewhere, I have measured a number of caps with no resistance values that looked low. Any help you can offer is appreciated, thanks for your time.

[mon2]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

Remove all power.

Measure the resistance to ground of PM_SYSRST_L.

[ronyan]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

Remove all power.

Measure the resistance to ground of PM_SYSRST_L.

I have 17.56 K Ohms measuring PM_SYSRST_L on R1995.

[mon2]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

To confirm, meter is in resistance mode,

One meter probe is on PM_SYSRST_L

Other meter probe is to ground ?

[reformatt]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

Review this thread. If you have CPU Vcore present during the double pulse, it is not a PM_SLP_S4 issue.

https://www.badcaps.net/forum/showth...ighlight=a1466

[ronyan]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

Review this thread. If you have CPU Vcore present during the double pulse, it is not a PM_SLP_S4 issue.

https://www.badcaps.net/forum/showth...ighlight=a1466

I have gone back and measured PM_SYSRST_L resistance to ground and it is 17.76 K Ohms, black probe on ground.

The Vcore to the CPU is double pulsing, and also PM_SLP_S4_L is double pulsing.

I also checked L7630 as I saw that being mentioned in the other thread, and it only has 7 Ohms to ground (on my boardview these are labeled PP1V05SS0_LL and PP1V05_S0_REG_R). I assume this is the issue?

[reformatt]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

7 ohms to ground on L7630 is usually a dead PCH on these. Should be 150 ohms or more. Obviously check around U7600 etc, but its often the PCH portion of the CPU that's gone.

[ronyan]

Re: Macbook Air 820-00165 board power pulsing twice and missing PM_SLP_S4_L

7 ohms to ground on L7630 is usually a dead PCH on these. Should be 150 ohms or more. Obviously check around U7600 etc, but its often the PCH portion of the CPU that's gone.

Yeah that's what I was afraid of, I removed other chips on that line (U7600 and Q7630) earlier hoping that the resistance would come up but no luck. Thanks for the help, at least I may get a donor board out of it if the guy wants to replace the logic board.