I wanted to use a powered USB hub with my RPi and it seems I did what is described here as back-powering because I first plugged in the powered USB hub before inserting the normal power cable. Unfortunately, then I also plugged in the normal USB power cable and since then even without everything but SD card and power cable the RPi doesn't boot anymore.
The red PWR LED is on but nothing else happens. The F3 fuse gets incredibly hot and between the points TP1 and TP2 I only measure 3.8V instead of 4.8V with another RPi and the same power supply.
I already waited more than 24h to let the F3 fuse come back but it simply doesn't work.
Any ideas how to bring back my first RPi?
Thanks in advance!