Prime does not turn on after charging

[Jean-Baptiste Boric]

(08-15-2019 04:02 PM)olr Wrote:  Thank you, i found it. I used the USB TTL cable, that i used to flash my WP34s. I think i did it right (echoing worked) but nothing was displayed in the terminal when resetting the Prime :-(

Assuming there's no manipulation error (like putting the TX wire on UART_TX), that's really bad news. Either there's something electrically wrong with the motherboard that prevents it from booting or the first NAND sector got somehow corrupted.

You can check if the motherboard is alive by probing the NAND chip with an oscilloscope to see if the SoC is talking to it. If it is (and the NAND chip isn't dead), your HP Prime can theoretically be fixed either with a JTAG interface to load and run the recovery in RAM or with a NAND flash programmer to rewrite the boot sector+recovery on the NAND.

I'd say the JTAG option is the only one with a reasonable chance of success, if you're not afraid to get your hands really dirty. Just in case, you probably want to contact HP and ask them if they're willing to take a look at it and repair it out of warranty (I assume you'd prefer maximizing your chances of having a working calculator at the end).