Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

[martyjelen]

Hello,

I need help with Macbook A1989. It stuck at 5V / 5mA.

I already do some measurements https://logi.wiki/index.php/CD3215_Bootup_Sequence

PP20V_USBC_XB_VBUS - 5V
PP3V3_UPC_XB_LDO - 3V
PP1V8_UPC_XB_LDOA - 1.8V
PP1V8_UPC_XB_LDOD -1.8V
PP1V1_UPC_XB_LDO_BMC - 0V

It's the same on all CD3215. There is no signs of corrosion or something like that.

What should I check?

Thanks for help.

Thanks

Martin

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Flip the power adapter cable by 180 degrees and test each USB -C port.

Need to have a voltage on:

PP1V1_UPC_XB_LDO_BMC

for the USB -C port being used to power the logic board.

This is the power rail this is used to communicate with the power adapter for the power delivery contracts over the CCx pins.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Thanks for reply.

Already checked all ports. It's all the same. There is no voltage on
PP1V1_UPC_XB_LDO_BMC

Checked all 4 CD3215 chips. Same problem on all of them.

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Remove all power. Meter in diode mode.

Red meter probe, yes red, to ground.
Black meter probe to the pin to test.

Measure the same BMC power LDO rails as above to check if there is a short on the rail.

Post each measurement.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

ub400
0.525
u3200
0.525
ub300
0.538
u3100
0.538

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

These are good readings and each is without a short on the rail.

What is the voltage to ground reading of PPBUS_G3H @ F7000 ?

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

It's shorted.

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Ok. Remove the fuse @ F7000. Then check again to see if PPBUS_G3H is available on F7000, pin # 1 (ISL = producer side).

Then remove all power -> meter in resistance mode. Measure the resistance to ground of F7000, pin # 2.

What is the resistance ? Do not do any voltage injection till we know more about the case. A high side mosfet short can kill the CPU / PCH.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Fuse is now removed.

There is a 12.26V on pin # 1
There is 0.2 Ω on pin # 2

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Would you have an adjustable power supply?

That can support 1 volt output?

Need to check one more section to be sure the CPU high side mosfet is not leaky. Then can inject 1 volt max onto the downside of the F7000 fuse pad. This will cause the shorted part to heat up and show it's face.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Yes, I have adjustable power supply. But I never done this before. Is it possible to do this without thermal camera?

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Yes it is.

With such a hard short, the component will heat up and crack under the pressure. You should be able to smell it. A simple trick is to pour the region with caps with IPA (pharmacy grade alcohol) and watch it mist from the heating action of the shorted part. We did this for a while.

Now we use the short killer product rated @ 30A. We dial up 0v8 (must be 1v or under to be safe) and apply this zapper. Often, the ceramic or tantalum cap that is shorted will crumble into pieces with this process.

See attached.

Remove all power. Meter in resistance mode.

One meter probe at F7000, pin # 2 (downstream = consumer side of this rail)
Other meter probe @ L7210, pin # 2.

We are checking if the high voltage rail created by the ISL (PPBUS_G3H) is shorted internally through high side mosfets inside the CPU power rails.

If yes, then likely the CPU is toast from the same event.

Either way, you can inject 1 volts onto the PPBUS_G3H and check the current of your power supply and watch for the component (likely a capacitor) to heat up and crumble.

For now, share the resistance reading of the above.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

It is about 5Ω.

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

To confirm, you are reading a 5 ohm resistance between PPBUS_G3H and the inductor / coil referenced in my last post?

That is bad news. This means that the high side mosfet inside the switch regulator is shorted and very likely passed the high voltage from this rail onto the CPU / PCH and killed it.

Do wait on others to comment but the CPU will have to be replaced which is not a simple process.

[piernov]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Assuming no direct short PPBUS_G3H → PPVCC_S0_CPU:
resistance PPBUS_G3H→GND = 0 ohm
resistance GND→PPVCC_S0_CPU = 5 ohms
resistance PPBUS_G3H → PPVCC_S0_CPU = resistance PPBUS_G3H→GND + resistance GND→PPVCC_S0_CPU = 5 ohms

If direct short PPBUS_G3H→PPVCC_S0_CPU and no direct short PPBUS_G3H→GND:
resistance PPBUS_G3H→PPVCC_S0_CPU = 0 ohm
resistance PPVCC_S0_CPU→GND = 5 ohms
resistance PPBUS_G3H→GND = PPBUS_G3H→PPVCC_S0_CPU + resistance PPVCC_S0_CPU→GND = 5 ohms

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Excellent. Thanks @Piernov.

Let us continue...

Remove all power -> meter in resistance mode -> check the resistance to ground of L7210, pin # 2.

What is the measurement?

How current can your power supply support?

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Thank you very much guys I really appreciate your help. I will reply tomorrow.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

So, I checked it again.

F7000, pin # 2 > L7210, pin # 2 - 5Ω
L7210, pin # 2 > GND - 5Ω

Current limit of my power supply is 5A.

[mon2]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Dial up 1 volt on your power supply.

Mate the red probe of your power supply to F7000, pin #2 pcb pad. Black probe to ground.

Do not have any other power to the logic board.

This setup will inject 1 volt onto the shorted component on the logic board and will cause that part to heat up quickly. Note which part heats up. Often will be a defective capacitor which will often crack open. Then turn off this dc power supply and check the resistance to ground again at F7000, pin #2.

[martyjelen]

Re: Macbook A1989 - 820-00850-A Won't turn on - stuck at 5V/5mA

Ok, thanks. And how much amps?