try hold the reset button for about 10s.
it's a pity that void the warranty if the router is defective after updating the third-party firmware,

Adam Cox wrote

try hold the reset button for about 10s.
it's a pity that void the warranty if the router is defective after updating the third-party firmware,

This way not worked because I upgrade the router to the OpenWRT linux software .
any one have any ideas ?

I have same problem too. What should I do? :-(

Hi,

Sorry to hear, as for the OpenWRT - especially the Huntsman firmware is great - is normally does not cause your route to be bricked. Try the following:
At the back of the router (next to the blue WAN port) there is small reset button.
Step 1: Press and hold the reset button for 30 seconds then while still holding the button, disconnect power.
Step 2: Keep holding the reset button for another 30 seconds then plug the power back in and continue holding the reset button for another 30 seconds
Step 3: Release the reset button and let router boot.

This is called the 30, 30 ,30 second reset :-)

Let the router boot and after a while you should see a TP-LINK_########## wifi network from your PC or Laptop. Have a look at the bottom of your router there is a big label. At the bottom right of that label, there is a SSID and a KEY. This is your routers default wifi - use that key to connect via Wifi to your TP-LINK_######### wifi. You should now be able to access the config page of the router by either 192.1681.1 or 192.168.0.1 webpage (might have to give yourself a static ip. Load the first release Firmware from TP-Link back onto your router and all should be back to normal. No you can try to load the OpenWRT firmware again or stick with TP-Link firmware.

BIG NOTE!
Before loading the OpenWRT Firmware, you HAVE to reset the TP-Link Router to factory default !! Otherwise you will have this kind of problem.

All the best

There are some tips for recovering your OpenWRT router here.

http://www.rfactory.org/OpenWRT/unbrick.html

Cheers

John k

Model : TL-MR3420

Hardware Version : V2
[COLOR=#000000][COLOR=#000000][COLOR=#000000]

Firmware		OpenWrt - With X-Wrt and Vibe Extensions mr3420-20141029
Kernel		Linux 3.3.8 #44 Thu Feb 28 13:56:12 GMT 2013
MAC		10:FE:ED:8D:BB:CD
Device		Vibe Appliance Powered by TP-Link
SBO4VOIP		3.089
CPU		mips
Username		admin

Web mgt. console		Webif² SBO4VOIP
Version	[/TD] [TD] mr3420-20141029

[COLOR=#000000]==============================================

SBO4VOIP running on OpenWRT r33212
[*]SBO4VOIP version: 3.089
[*]Host: OpenWrt

** ANY ONE PLEASE HELP ME TO HARD RESTORE OR GO TO NORMAL TP-LINK FIRMWARE**

[COLOR=#000000]

MR3420 is a great router, have been using it for almost a year. The original firmware has some problems because when it switches from WAN to 3G it sucks there. The fix for me was this tutorial Fix TP-Link TL-MR3420 v2 3G/LTE Failover . Since there the routers works flawlessly.