Hi all, second post. Have bricked NVR. With lots of help from here, I got as far as connecting Putty to the serial port and also setting up a Hikvision tftp server. I end up in a loop in tftp, connect success and start file transmitting. Never got to completed. Same problem with both versions of TFTP. When I look at the serial console, it looks like it downloads 31MB pretty quickly, then spends about a minute trying to retry, with the screen showing a "T" about once a second, which is probably the retry , finally failing and starting over. The DAV file is 54MB. nvr_k51_bl_ml_std_v4.21.005_109509_0 , anybody familiar with getting TFTP to work. My PCs are all currently Windows, mostly 10, but also W7, and XP. If I must, I could build a laptop with Linux. Thanks