bricked Hikvision NVR (DS-7716N/16P)

Hi

I have bricked my NVR... Its a DS-7716N/16P . It boots now with constant beeps (maybe 10-15 beeps) and then reboots. I have downloaded TFTP tool from Hikvision. But it it cannot connect to the NVR. I can ping the address of it (192.0.0.64) but in TFTP it never sees it. I have tried turning off the firewall but no success. Is there any other way (serial) to recover the bricked NVR ?

Thanks for any help!

Regards

Joe