6s with dead PP1V8

Hello folks,

I have a weired acting 6s here. First it came with dead. It had a short on Vcc main (C3618_F ) which I replaced. Short is gone but now the trouble starts.

First of all it looks like someone already repaired the backlight (the customer hadn’t had it repaired and just bought it used).

So the history is…it worked until they exchanged the battery to a not original one (2,1A instead if 1,8Ah).

My current measurements look as followed

DCPS on 4,2V

Vcc main = 4,2V

Vcc Batt = 4,2V

PP5V0 USB - 5V

PP3V0_Tristar - first there are 3V but then it starts jumping to 0 and to 1,7V and back to 3V but it’s never constant voltage

PP1V8 - 0V

PP3V0_Nand - jumps aswell from 3V to 0 (like PP3V0_Tristar)

PP_CPU - jumps aswell from 0,8 to 0V and so on

PP_GPU - 0V

According to my dcps there is no other short and I measured the resistances of those lines and had those results:

PP1V8 - 70kOhm

PP_CPU - 110Ohm

PP3V0_Nand - starts at around 20MOhms and goes up to 40+

PP_GPU - 30Ohm

I tested the tristar with a tristar tester and no failure found. I never had such a heavy defect on a board and I’m uncertain if this could only be caused by a defect U2000 (pmic). Since I have never heared of this one being defect.

Could anyone give me a hint on what to inspect/check or if it’s better to just let it be and trash it?

Thanks in advance