A1534 Macbook 12" no voltage on PPVCC_S0_CPU

[Fyod]

I'm troubleshooting this board and input rails seem fine.
Board is in good condition, no liquids damage, no corrosion, no bad caps that I can see, nothing getting warm. Someone was inside and broke the keyboard flex so I can't try SMC reset, unless there's an on-board way to reset. The board negotiates 20V from a PD charger.

I don't have an inline volt/amp meter for USB-C, so I continued by using a 5V Anker power bank and inline 5V meter to see amperage. There is no current draw, only 10mA every 15 seconds or so (without battery).

I measure 8.6V, 5V on the appropriate rails, and 3.28V on PP3V3R3V0_AON.
No voltage except some blips on PPVCC_S0_CPU.
PPVCC_S0_CPU is 67Ohm to ground.

If I put the board back in the bottom case to charge the battery, initial power draw is 0.4A, then 0, then 1.5-1.7A (5V) so it seems that the battery is charging, although the large pads on the battery only measure 300mV (wtf?), even though I left it charging for about 4 hours (was drawing ±7.5W the entire time).

Any pointers or ideas?

Edit: CPUVR_PHASE1 nor PP5V_S0 present.

[disorder]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

hello, if keyboard connector is broken, remove it first. it can cause dead mbp

[Fyod]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

Not the connector, someone snapped the flex cable that connects the halves.
https://images-na.ssl-images-amazon...._AC_SY355_.jpg
I have of course removed it.

[Fyod]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

PP5V_S4 is present, 4.95V
PPBUS_G3H is present, 8.60V

[Fyod]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

Today I went back over the rails and nothing that enables S0 state has voltage. I can't remember the rail that looks to enable all S0's (labeled S0 Enables in the schematic), which should be 3.3V, and is also 0V. Will specify when I get home. Edit: PM_SLP_S3_L

So it seems to me that the board is stuck in S4 deep sleep. I'm wondering if I get a replacement keyboard flex whether PRAM reset could wake it up?

The board seems totally fine, just stuck in a state that won't allow it to turn on (to S0). I poked around all over the place looking for shorts but everything is kilo to megaohms.

I realized that the battery probably has circuitry that doesn't allow ~8.6V to be present on the large connecting pads as a precautionary measure, unless the main board communicates with the battery board.

I also watched one of L. Rossman's vids where he bypasses an S0 enable gate to get the board to wake up, but I'm holding back on soldering anything until there's no other way out. The A1534 doesn't have a gate for S0 and it looks that all states are regulated by U7400 (iirc).

[piernov]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

Are you sure you have PP5V_S4? What about S3 rails?

PS: Note that A1534 will always end up with dead CPU.

[Fyod]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

PP5V_S4 is stable and 4.995V
P5V_S4_PGOOD is stable 3.3V
PP3V3_S4 is 0V (70K to gnd, no short), edit: PP3V3_S4 goes to 0.07V three seconds after plugging in power, then gradually goes to 0V in about five seconds.
P3V3_S5, P3V3_S5_PHASE are stable 3.3V
PP1V2_S3, PP1V8_S3, PDDR_S3_PHASE are 0V, no spikes
PM_SLP_S5_L is stable 3.3V

Considering that P3V3_S5 is VIN for U8000 and PM_SLP_S5_L is the trigger, PP3V3_S4 should be 3.3V (but isn't).
Unless PM_SLP_S5_L is supposed to be LOW to switch U8000.

Could PP3V3_S4 be the reason it isn't going into S3?

I have read about the CPU failures, but I'm not going to give up just because of them. I don't mind spending time on this board, I'm going to keep it, there's no profit for me in it, just learning experience.

[piernov]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

If PP3V3_S5 is 3.3V and PM_SLP_S5_L is 3.3V, PP3V3_S4 should indeed be 3.3V as well. Check if U8000 looks chipped/cracked under microscope.
Usually PP3V3_S4 is not required to get into an S3/S0 state, but I don't know for this exact board. It's required for several peripherals though.

When they are high, PM_SLP_S5_L enables S4 rails, PM_SLP_S4_L enables S3 rails and PM_SLP_S3_L enables S0 rails.

[Fyod]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

It looks fine, but I can try to reheat it for the hell of it tomorrow.
Also, I edited my previous post, because this is weird - PP3V3_S4 goes to 0.07V three seconds after plugging in power, then gradually goes to 0V in about five seconds.

[Fyod]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

Interestingly, PP1V05_SUS is 1.05V stable.

[piernov]

Re: A1534 Macbook 12" no voltage on PPVCC_S0_CPU

SUS comes up between S5 and S4.