Tablet won't charge - reboot loop

Hey there,

I've got a tablet here which I offered to repair for free if I could. The issue was that it wouldn't charge so I changed the charging port with the ribbon cable which was obviously faulty.
However, this didn't fix the problem.
I am getting a battery symbol with a lightning which continuously loops.
I replaced the battery then since it showed 3.3V and I expected it to be dead.

With the precharged battery, the tablet turns on now, but it won't charge. The battery is not red crossed.
When the tablet is off, I still get my boot loop with the flashing battery icon.

I've tried hard resets like Power + Vol Down/Vol Up, Home which I found in my research. Maybe there is one I missed, so help is appreciated.
Power down leads to flickering without a battery symbol (0.5s).

I've also had the idea that the power supplies may were insuficient. I used an external power supply to provide at least 5V and 2A (via the USB cable) Those are my observations:
- NO current draw when the tablet is on
- 0.08A up to 0.92A for a short moment when the battery symbol shows up
- 0.08A in recovery menu
- Flickering after powering down: 0.02A (constant)

Now it gets interesting: when the boot loop is started (cable connected) and the display ribbon is disconnected, the current rises from 0.92A to 1.15A (for short moments). So it uses more energy to NOT power the display than to power it.


I feel like there's a software issue but I've not yet found a solution for that. Can anyone help me with that?

Otherwise I see two options:

- Lower the voltage of the charger to 4V and directly connect the battery to it
- Power the tablet directly with 5V without the battery: I've done that with a phone before but since the tablet is not mine I'd prefer a safer option. The owner has agreed on risking it though (before he knew the tablet was starting with the new battery).

Help is very appreciated.