02-19-2024, 07:30 AM
After EVEN MORE debugging and making sense of the schematics, here's what it looks like:
The TXS0104ED chip isn't supposed to provide power to the EM85F684A microcontroller unit (MCU).
However, they both share the same V33 input of 3.3 volts, coming from the ME6206 voltage regulator, a tiny chip on the mainboard.
Moreover, the 3.3 V input coming from the USB debugging pads is also connected to V33.
And it looks like the ME6206 is faulty. This is why the MCU is off all the time, unless powered via the USB debugging pads, which provide the power directly, after the ME6206. At least this is what it looks like to me. I hope I'll get the chance to order an equivalent replacement for the ME6206 and solder it to the mainboard.
In the meantime, I also ordered a new mainboard from PINE64... At least it's not an entire PPKB.
The TXS0104ED chip isn't supposed to provide power to the EM85F684A microcontroller unit (MCU).
However, they both share the same V33 input of 3.3 volts, coming from the ME6206 voltage regulator, a tiny chip on the mainboard.
Moreover, the 3.3 V input coming from the USB debugging pads is also connected to V33.
And it looks like the ME6206 is faulty. This is why the MCU is off all the time, unless powered via the USB debugging pads, which provide the power directly, after the ME6206. At least this is what it looks like to me. I hope I'll get the chance to order an equivalent replacement for the ME6206 and solder it to the mainboard.
In the meantime, I also ordered a new mainboard from PINE64... At least it's not an entire PPKB.
