I’ve now had 5 carriers die. 3 NX boards and now a second Nano B01 board. All power related.
This time, the 3V3 power rail seems to only be able to supply a miniscule amount of current. Just enough to make an LED glow very dimly. AND when anything is connected to 3V3, even the LED, even the board’s power led won’t light until the kernel has booted enough to switch on the regulators. In fact, there isn’t even enough 3V3 to create reliable output on the TCU port.
Once the kernel has reached the point of initializing the regulators, the power LED comes on and TCU outputs enough to cause a serial-usb converter to work. The 3V3 pins on the 40-pin header never get enough power to anything other than make a LED glow dimly… I’m guessing the TCU now works because the module’s own regulators have been initialized.
Other than an RMA, there’s not much to do, I know. Someone should look at the sourcing of the power components though.
Oh, just fyi… None of the board that failed were operated in harsh conditions and all used power supplies matching the specifications for their hoards.