There are several common issues that you can face when powering up the BBC Micro and some of the solutions are listed below.

This is basically the ROM or configuration failing to load.

It can be a simple case of cleaning and re-socketing the ROMs that are installed in the 4 ROM slots.

Alternatively it could be the CMOS battery on the circuit is dead and needs resetting. To do this replace the battery with a fresh one, turn on the Micro while holding R to tell it to reset the CMOS. It will ask you to press Break. Hold F then press and release Break. The Micro should restart and have an asterisk waiting for input. Type the following to reconfigure the Micro back to stock.

Press CTRL-BREAK to restart and you should be good to go.

If this appears on boot, this is usually again just a poorly socketed ROM chip or bad ROM.