macbook 820-2850-A no PM_SLP_S4

[audiomodder]

hey folks,
working hard on this one and I'm pretty stuck. PP5V_S5 was originally shorted dead to ground because of a bad cap (C6213). In the process of finding that, I injecting 5V into the rail to see what would heat up...which didn't help much.
I removed the audio amps, removed and replaced U7300, removed and replaced U5930 (accident).

My problem appears to be no PM_SLP_S4 (its stuck low, though not shorting).

PP1V05_S5 - 1.04V
PP3V3_S5 - 3.3V
PPBUS_G3H - 12.57V
PP3V42_G3H - 3.34V

I injected 5V into PP5V_S5 and it draws very little, so I think the short is no longer the issue now that the cap was removed. But maybe it shorts when EN lines are activated? I notice that it is ~10ohms to GND when magsafe is plugged in. My scope shows nothing pulsing on the lines either.

Should I remove U7300 (TPS51116) again ? Or remove U6201 (audio decoder)? these are the best candidates for 5V_S5 issues...though I'm not sure if I should be looking for something else..

Thanks!!

[audiomodder]

Re: macbook 820-2850-A no PM_SLP_S4

Small update,
turns out I have a working board of the same type to take measurements from. With diode checks everything matches up, 3.99-0.4 for PP5V_S3 and PP1V5_S3 from U7300 (TPS51116) checks out.

Problem seems to be when power applied, PP5V_S3 measures ~8ohms to ground. Yuck.

Then, *magically* one time (out of the 50 times power cycling) it actually booted! This was not able to be repeated.

So I am thinking it is a cap problem. I went and removed every single cap connected to PP5V_S3...no dice. I'm thinking is have to be something shorting internally when an EN pin is active on one of the chips then. What a mess.

Should I just take out the audio encoder and U7300? Or maybe inspect around U7201 more to see if there's something missing? No water damage though, it is a clean looking board. Oh how I wish so hard there was a in like fuse with PP5V_S3 so I could at least rule out U7201 as the problem.

[audiomodder]

Re: macbook 820-2850-A no PM_SLP_S4

Another update:
So I did a little trick to test PP5V_S3: I removed the resistor to PM_SLP_S4 (R7912) and ran a 100K resistor from the R7912 input to PP3V3_S3 output. That way the 3.3V working rail doubles as an ENABLE for the 5V rail of U7201.

That totally worked. Now I know my 5V is not the issue, or at least it highly unlikely.

but PM_SLP_S4 still isn't there and I don't know why. Can someone point me in the right direction on this one? I'm hoping it isn't an issue with U1800. It looks like U1800 generates its own clock signals (built in PLL) but I don't know which voltages / signals it needs present to activate PM_SLP_S4 .

[piernov]

Re: macbook 820-2850-A no PM_SLP_S4

PCH needs RTCRST#, SRTCRST#, INTVRMEN# and RSMRST# for it to initialize. The first 3 signals should always be present.
RSMRST# is not present when the machine is turned off on battery, it may be present with AC adapter connected and machine off (I don't know about Apple). It must be present as soon as the machine tries to turn on, and must be present before PWRBTN# goes high again. This is managed by the embedded controller, the SMC in Apple devices.
PWRBTN# triggers the PCH to change power state (S5→S4→S3→S0).
Also the PCH will need to communicate with the SPI ROM.

[audiomodder]

Re: macbook 820-2850-A no PM_SLP_S4

Thanks for the SUPER informative reply piernov! Thats exactly the kind of info I've been needing for a while...

So just for the hell of it I tried another 85W charger and...it boots + works now!! Whatthehell apple. The other charger had green light, rock solid 12.6V, 3V42, etc.. so *shrug* I'll test it in a couple days again to make sure it isn't something else. But I sure am glad I didn't pull all the PP5V_S3 parts. I still have to replace those BGA amps I removed though... >_<