A broken cable would not cause the board to beep.
All peripherals are just connected by RS232, that would never cause the board to beep, it would just not work.
Go to the manual of the board and look out for the beep signals...
Could also be the Display has died, or at least try to flash it.
Standby and Reel Multmedia is not flashing, if I am right you have to press the button right beside the On/Off and then in parallel turn on the Power Switch.
The red Led would light up, this is signalling that the Display is flashed again.
Are you sure that you connected everything the same way when you restarted the board first time.
Worst case you can kill the RS232 converter on the small power platine if you do wrong...
Best regards