Fuses in Macbook Pro 2019 A2159

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Ok. So the eDRAM switching regulator is NOT enabled.

Check for the presense of PP3V3_S5 rail which powers the logic that drives the eDRAM rail regulator.

See attached.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

PP3V3_S5 = 3V3, this is at both ends of each of these resistors.

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

That is a good sign and is the voltage that powers the logic gates that ENABLE / DISABLE the eDRAM switching regulator.

Yet, the power rail is being DISABLED.

See attached. Post the voltages for the signals used to make this decision.

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Also, check if the 1v8 rail is present in the revised attachment location.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

R7792 near the U7790 level shifter = 1.2mV, then goes to 100mV for about 10 seconds, spikes to about 1V (fraction of a second, multimeter goes through the ranges) and back to 1.2mV for about 40s, repeat.
R7792 opposite side of level shifter (upper end on photo) = 1.8V for about 40s, then 0V for about 10s, repeat, similar with golden pad below it from last post.

R7103 left side whete arrow points = 1.8V for some seconds but unstable, drops to 1.5, 1.2, hundreds of mV, zero, back to 1.8V, no clear pattern.
R7103 opposite (right side closer to U7712) - fluctuates, no pattern, 0...200mV with possible spike around 1V.

The above are difficult to measure precisely without oscilloscope hope this helps...
These times are not rigid, I think as the board warms up they patterns get more chaotic.

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

See attached. Interested in the voltage @ L6900.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

See attached. Interested in the voltage @ L6900.

3V3, appears steady

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage of R7103 from another part of the logic board.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage of R7103 from another part of the logic board.

1.8V for about 40s, then 0v for a few seconds, then 0.3V for a few seconds, then repeat to 1.8V

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Remove all power. Meter in resistance mode (2k).

Check the resistance to ground for the same test point for the 1v8 rail that is pulsing.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

Remove all power. Meter in resistance mode (2k).

Check the resistance to ground for the same test point for the 1v8 rail that is pulsing.

Board drained, 980kOhm in ref to GND

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage of PP3V3_G3H_PMU_VDDMAIN as per attached location.

Your 1v8 rail is pulsing ON / OFF. Need to confirm that the INPUT to the regulator that creates this rail is stable or not.

There are many spots on the board that can offer this voltage check but the test pad looks convenient.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage of PP3V3_G3H_PMU_VDDMAIN as per attached location.

Your 1v8 rail is pulsing ON / OFF. Need to confirm that the INPUT to the regulator that creates this rail is stable or not.

There are many spots on the board that can offer this voltage check but the test pad looks convenient.

Continuous 3.3V there

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Check the presence of PP1V8_AWAKE.

Also, PP1V2_AWAKE.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

PP1V8_AWAKE = continuous 1.8V
PP1V2_AWAKE = continuous 1.2V

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage for PP1V8_G3S.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

PP1V8_G3S = 1.8V
note to this and previous 1.8V measurements: every 30-60s the 1.8V goes to zero, jumps to 2.1V momentarily and back to 1.8V for another 30-60s

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage for the attached.

[mp844]

Re: Fuses in Macbook Pro 2019 A2159

Post the voltage for the attached.

+3.3V continuous

[mon2]

Re: Fuses in Macbook Pro 2019 A2159

See attached to see where we are at.

The power sequence just after this last checked rail is pulsing.

You may have a SMC fault but wait on other comments. Perhaps reflashing the BIOS will help but no direct experience with this area. We should have 2 of these boards in next week for repair so can check and post updates at that time.

The fault could be linked to corrupt T2 firmware but have not yet reflashed such logic board. Believe @Stephen is the pro in this area here in the forum.

But wait for more advice:

https://www.badcaps.net/forum/showthread.php?t=93978