820-00840 Strange USB Problem


Hello. This board came to me with no life. Shorted 3V3 line. Corrected that problem and the board started. Everything works fine except for USB/Thunderbolt/HDMI. I have a Satechi USB-C hub here which I use on all my personal Macs and use it to test all costumer's Mac, So I know it's working fine. But on this particular board, I can charge the Mac using the USB-C port on the hub on both ports but USB/HDMI don't work. Well, they kind of work, just on EFI. If I press option during boot, USB drives mount on boot selection screen, but when the system starts loading it loses communication. If I leave it connected for 10 minutes or so, it starts loading the installer again and completes boot. Same if I start MacOS. If I connect the hub with a USB drive attached to it the system does not recognize it, but after 10 minutes connected the drive magically mounts and starts working. If I unplug it and plug it again it will work only after 10 minutes connected again. HDMI never works. BUT, with a much less sophisticated USB-C to USB adapter from TPLINK I have here, USB works on one port but not on the other. I already replaced both CD3215 and thunderbolt controller (U2800) and tried flashing BIOS. Same thing. Any ideas?


Staff member
If you leave it stay on boot menu, USB device disappear after some time?
Do not start macOS loading.

Test with USB mouse if is always recognized before and after logedd into macOS.
Just try to diagnose if problem is related with USB 3 mode only.