I did it these by wireshark it shows me the router is looking for TFTP server recovery file with ip address 192.168.0.66, the file name mr3420v2_tp_recovery.bin I read some time back from some form for another tp-link router recovery, it took all about 12 hour to search read configure and solve. Hold the Tplink router rest button before switching on the Tplink router router and you will see that 192.168.0.88 will access the file after you see message on the TFTP with name of the file mr3420v2_tp_recovery.bin recovered, then release Router rest button, change computer ip address to "obtain Ip address" switch off the router and switch it on, and here you are getting the new ip address on the computer and router LED will be stable now you can login with the new ip address through web.
Setup from solarwinds TFTP menu, the server directory where file mr3420v2_tp_recovery.bin is saved. "I gone through brick issue as configure the openwrt for testing, the TL-MR3420 TP-link router, but recovered through TFTP server it quit easy no need for console port an, use the solarwinds TFTP(i am using since 15-18 years now) TFTP server, now change the firmware name to mr3420v2_tp_recovery.bin, connect router and computer on single Ethernet straight back-2-back cable, change ip address of computer 192.168.0.66/255.255.255.0 without putting any gateway address, now switch-off all the computer firewall options on the computer Ethernet port, as TFTP required udp 69 port to access, but anyway if the firewall is not blocking the port then it is ok.
I got this from a commenter named "vivoizer dialer" on my youtube video on the same. Welcome to Martview-Forum, A Free Discussion Forum About Simlock, imei Repair, firmware upgrade, FRP reset, phone unbrick solutions ,boot repair & all.
There is a less tedious way to debrick these routers.