General question about MacBook power rails for repair.

[SarcasticOP]

I am looking at an A2337 and found this for the order of power rails and what they do. Can this be confirmed before I dive into hunting down power rails that do not exist or are not neccisary?

• PPBUS_G3H (12.6V-12.8V)
  • This is the main power rail that supplies power to the entire system. Check this rail first, as it must be present for other power rails to work.
• PP3V42_G3H (3.42V)
  • This power rail is derived from PPBUS_G3H and is used to power the SMC (System Management Controller) and other essential circuits. It should be present if PPBUS_G3H is working correctly.
• PPVRTC_G3H (3.3V)
  • This rail powers the real-time clock (RTC) and the SMC in standby mode. It is critical for maintaining the date and time and for the SMC's operation.
• PP5V_S5 (5V)
  • This rail powers components that need to be on during the S5 (soft off) state. It should be present if the MacBook is plugged in.
• PP5V_S3 (5V)
  • This rail powers components during the S3 (sleep) state. It should come up when the MacBook wakes from sleep.
• PP3V3_S5 (3.3V)
  • This rail powers components that need to be on during the S5 state.
• PP3V3_S3 (3.3V)
  • This rail powers components during the S3 state and should come up with PP5V_S3.
• PP5V_S0 (5V)
  • This rail powers components when the MacBook is fully operational (S0 state). It should be present when the MacBook is turned on.
• PP3V3_S0 (3.3V)
  • This rail powers components during the S0 state and should be present when the MacBook is fully operational.
• PP1V05_S0 (1.05V)
  • This rail powers the CPU and other low-voltage components during the S0 state.
• PPVCORE_S0_CPU (varies)
  • This rail supplies power to the CPU core. The voltage varies depending on the CPU's workload.
• PPVCC_S0_CPU (varies)
  • This rail supplies power to the CPU's integrated GPU and other components. The voltage also varies.
• PP1V8_S0 (1.8V)
  • This rail powers the memory and other 1.8V components during the S0 state.
• PP1V2_S0 (1.2V)
  • This rail powers additional low-voltage components during the S0 state.

[mon2]

Hi. No. The above is for the older macbook models. The A2337 is the pain in the arse, M1 design. This unit operates with USB power delivery. There are plenty of details of this model here and repairwiki, etc.

Start with the using only a suitable rated power adapter. 100W with 100W rated power cable is recommended if the original power adapter is not available. Place a USB Type C meter (bidirectional type) in the middle of this power adapter and your logic board. This meter will tell you if the power delivery chips on the logic board are working or not. If you do not have 20V, this needs to be fixed from the start.

Share if you have 20V and also the current draw showing on this USB type C meter. We can go from there.

[SarcasticOP]

It sits around here, the lowest is .3a with a one-time high of .601a.

EDIT: This is using a 140w Apple adapter with a 240w USB-C to USB-C cable.

[mon2]

Ok. This confirms that each of your CD321x PD controllers are working since you have 20v negotiated with the external type C power adapter. Good.

Carefully, measure the voltage to ground of PPBUS_AON @ fuse F5200. Check both sides of this fuse. This is a critical main power rail for the board. What is the voltage to ground? This is like the older PPBUS_G3H power rail.

[SarcasticOP]

12V on both sides of F5200

[mon2]

At 12v, the PPBUS_AON is not boosted to the normal ~13v level. This 13v level is selected using the I2C / SMBUS interface (SCL / SDA lines).

Remove all power. Disconnect the battery @ J5150. Meter in resistance mode.

Measure the resistance to ground of the SMBUS lines (SCL / SDA). One meter probe on the pin to test. Other probe to ground. What is the resistance?

We are checking if either of the TVS diodes that mates with the SMBUS lines is defective or not. If yes, this can shunt the communication lines used by the ISL9240 buck boost regulator that is reporting to be at 12v and not 13v.

[SarcasticOP]

So before I did that, I rechecked it since the last post told me to disconnect the battery, and when I took it at 12v, there was no battery attached. I re-did the check with the battery attached, and I got 12.72 on one side, and 12.73 on the other. Should I proceed with the recommended steps above or look somewhere else due to the change in reading with the battery attached?

[mon2]

No. Not necessary. If I recall correctly, some motherboards and perhaps this one, will only boot if there is a pre-charged battery mated with the board. You are in the valid range for PPBUS_AON.

So what is wrong with this unit? Allow for the usual time to boot to login screen and then press the keycaps key. Do you see the caps key led toggle on/off after a keypress? If yes, the board is booting and you are the login screen.

If not, carefully, measure the voltage to ground on each and every inductor on the board. Each inductor is linked to a local power supply rail that is taking the PPBUS_AON voltage and lowering it to another voltage (buck regulator design). Check if there are any low / zero volts on the inductors. Check against the schematics. If found, that rail is a suspect.

[SarcasticOP]

It charges at the rates above but will not power on.

I will let you know when I have all the info to provide back to you.

I am assuming check voltage with battery installed?

[mon2]

Try a DFU to the unit.

[SarcasticOP]

No response from Apple Configurator on a different Macbook when trying to put it into DFU more or trying to start it normally.