820-00928 - 20v but won't turn on

[Palhano]

The logic board without oxidation. customer reported that it stopped working.

It has 20v, pulls up to 1.8a and drops to 0.2a. I've seen this with a shorted SSD line, but I looked for a short on the board and didn't find it.

CD3215 LDOs all normal.

PPBus 12.6v
PP3V3_G3H - 3v3
PP5v_S5 - 5v

I have voltage on the SSD lines the moment I pull 1.8a.

 

[2informaticos]

Did you test with 87W charger?
Also test w/ and w/o battery connected.

With 20V/0.2A there must be more voltages present on the board; check CPU core then.

 

[Palhano]

Sorry, I put 0.2a and it's 0.02a.

Yes, charger 87w and original.
It only showed fast 1.8a without the battery. With the battery it was always 0.02a

The board now no longer pulls to 1.8a. when I plug in the charger it shows 5v, 0.24a, in a second it changes to 20v and 0.02a

 

[2informaticos]

Disconnect J9600 and test again.
If still the same, you can try known good BIOS.
First, compare diode mode readings on all coils with good board.

 

[Palhano]

I tested it without the J9600 and also tried it with another BIOS. Same problem.

I don't have a board of this model that is good for comparing coils. I compared it with annotations from a flexbv boardview and they look OK.

 

[2informaticos]

Test SMC bypass mode.

 

[Palhano]

I already tested it, it doesn't give any signal

 

[2informaticos]

Check for voltage pulse on all coils, when the board pulls 1.8A.
Check USB-C meter indication when trigger SMC_ONOFF_L.
Also check for drop pulse at PM_PWRBTN_L (at same time).

 

[Palhano]

the board no longer pulls 1.8a.

A similar Mac came in to change the battery, I took the opportunity to compare the coils in diode mode. Little difference, an example: the good board the L7211 appears 0.003, the bad board 0.007

 

[2informaticos]

Difference on the CPU core may be duoe of different CPU type.
i7 always gives lower values.

What about other tests mentioned?

 

[Palhano]

Meter does not change and PM_PWRBTN_L pulses when I activate SMC_ONOFF.

 

[2informaticos]

PM_SLP_S4_L pulses at same time?

 

[Palhano]

PM_SLP_S4_L does not pulse

 

[2informaticos]

Do you get 3V3_S5/SUS?

 

[Palhano]

Yes, I have 3.3 in both lines.

 

[2informaticos]

Check PCH's RTC signals.