820-01521 USB-C ports cycling

[overshoot]

Hi,

I have that board that was previously worked on.
Customer told me the laptop did shut off while working, battery was charged or at least partially charged.
When I got the board, the amp meter was showing nothing.
Upon inspection the USB-C area was reworked as well as the as the U7000 area.
I went ahead and replaced both CD3215 from a donor board as well as U7000.

Now I am getting the ports to cycle.
5V at 0.3A then 5V at 0.15A and cycle.
Both ports, both ways will do that.
Sometime it goes to 5V 0.5A and stays there.

Under thermal cam I can only see the PMIC getting warm (50 degrees C)
T2 around 40 degrees.

I've reflowed the CD3215 area, checking for bad solder connections.
I've replaced the MUX chip.
I've checked the diode mod on the TBT ROM pins and all good.

Can this be a board stuck in DFU or am I dealing with a dead T2?
Tomorrow I'll attempt the PMIC replacement but if you have any hint in the meantime, please share.

 

[2informaticos]

Check diode mode to ground on all coils; from secondary power suppplies.

PPBUS_G3H and 3V3_G3H_RTC fluctuating too?
What about U7800's LDOs?
ALso check its SLPS2R and AWAKE voltages.

 

[overshoot]

PPBUS_G3H is definitely fluctuating. When ampmeter is on, it seats at 12.3V and then shuts.
However when the ampmeter measures 5V 0.5A, PPBUS is at 8V slowing raising up.

PP3V3_G3H_RTC is definitely not stable, even when the ampmeter is on.

Well I guess the CPU is toast: L7821 and L7822 measures 3 ohms to ground and L7820 and L7819 measures 27 ohms so...

 

[2informaticos]

Very likely dead CPU.
These readings are from good board (diode mode):
L7819/20 308
L7821/22 260
L7823 276