A1706 Won't Turn on 20V/0.3A draw

[fharris1977]

I have a MacBook Pro Touchbar A1706 that won't turn on. With the board removed I'm getting 19.62V and an average amp draw of 0.300A. When I first plug in my ampmeter it goes from 5V to 19.62V after a second or 2 and the amp draw starts at about 0.688A and up to about 0.790A and then it gradually goes down to about 0.155A and works it way up to around 0.330A and then it fluctuates in the range of about 0.200A-0.350A. The voltage stays at 19.62V. Can someone with any experience with this issue help me out. I checked all the main power rails and they were present. Anyone know it would be greatly appreciated. Thanks in advance.

[mon2]

What is the voltage to ground of PPBUS_G3H ? Measure @ F7000 (fuse) - check the voltage on both sides to ground.

[fharris1977]

Hi. The voltage on both sides of F7000 is 13.06V

[mon2]

Good voltage. Is it stable?

Voltage to ground of ALL_SYS_PWRGD ?

[fharris1977]

Yep its stable. Voltage on ALL_STS _PWRGD is 3.247V

[mon2]

This confirms that all power rails are stable and this is the power good signal for each AND'd together = logic '1'.

Check the SPI flash. Measure the voltage to ground of each pin on the SPI flash (U6100).

Stable VCC of PP3V3_SUS on this flash device ? Check the voltage of each of the IO pins on this device.

[fharris1977]

SPI_MLBROM_CS_L=3.354V
SPI_MLB_IO1_MISO=3.345V
SPI_MLB_IO2_WP_L=3.344V
SPI_MLB_IO0_MOSI=0V
SPI_MLB_CLK=0V
SPI_MLB_IO3_HOLD_L=3.350V
PP3V3_SUS=3.357 stable

[mon2]

Have you checked the board with a thermal camera? To check for shorted components that may be causing the power cycling event.

[fharris1977]

No but I did the alcohol test and it evaporated pretty quick off of Q7030. The board was still in the housing though. Its not getting hot outside the board. I feel a little warmth but nothing is burning hot while plugged up outside the housing. I'll check my seek compact pro thermal camera when I find it. Haven't really used it since i bought it.

[mon2]

With no power -> test the resistance to ground of each coil / inductor to see if there is a partial short. Perhaps the power rails are cycling due to an excessive current draw of at least one rail. You can consider to remove the fuse @ F7000 and see if the power remains on without the cycling.

[fharris1977]

L7430, L7420, L7410 are 3.9ohm. L7210 and L7220 are 7.3ohm. R7220 is 11.3ohm. I don't know if these resistances are supposed to be that low. The other inductors are over 100 ohms or much greater.

[mon2]

Not at my desk but check the voltage linked to the inductor under test. If it is say 1v0 then yes, it is ok to have a low resistance. Will cross check later and update.