Issues with BIQU B1 printer - Printer not attached

[Ittalo Alvarenga]

Hello everyone. I would like to ask for help with an issue related to my BIQU B1 printer. I am a beginner in 3D printing, and this is my first printer, so I'm not quite adept at solving the problems that arise.

My printer is a BIQU B1, with the BTT SKR V1.4 control board, and apparently a BTT Legend Box V1.0 communication board (I'm not exactly sure of the name) with the Hot-end . I had to disassemble it for a renovation in my house, and when I reassembled it, I forgot to connect the USB-C cable between the base of the printer and the hotend. Consequently, I received the "printer not attached" message on the display, and I made the mistake of connecting this USB-C cable with the printer still powered on.

I connected it first to the hotend, and as soon as I touched the cable to the connector at the rear of the printer, I heard a very soft click and smelled a slight burning odor. Since then, my printer does not work, and the display shows that no printer is attached. I tested the fuses on the controller, and they are all intact. Also, when I connect a USB flash drive with some files, the printer can read the files, and the display works perfectly.

However, no sensor seems to send information to the printer. The temperature of the bed and hotend reads 0, and when I command the bed to heat up, nothing happens. The main fan of the hotend is also working, but the two side fans do not respond to the commands to turn on/off or change the speed.

I have no idea what to do or where the problem might be. I would like to ask for your help on which components to test with a multimeter or similar tools to try to identify and fix the problem, or to know which board is causing the issue so I can replace it.

I appreciate your assistance in advance.