PCB Track Damaged by Excessive Heat - WDR4300

Hi everyone, how are you? I hope well...

I'm Brazilian and here in my country I'm working with recovery of routers and communication equipment in general - An interesting technical assistance branch and Thanks to God, I've had a lot of service!

I would like your help if possible in the issue of the main board of a TP-Link WDR4300 router, received from a customer.

This router has corrupted fimrware. Recovering it would be no problem, but the client damaged the trail of the board where the TX pin of the serial port is, using a soldering iron with a very high temperature, as can be seen in the photo below.

So, I come to you, noble friends, to ask if anyone could tell me where this pin (TX) is connected, because if it is in an easily accessible location, I could get around this situation by making an external jumper. I decided to ask here, because searching the internet, I couldn't find the circuit board for this router (yet).

I also take the opportunity to ask: If not through the serial port, would there be another way to recover this router?
I know I can copy the entire contents of flash memory from an operational 4300, however what worries me is the data from the ART partition, the MAC-ADDRESS which will be the same as the "good" router, right? And without serial port access, I wouldn't be able to access the U-Boot prompt to change these MACs with the "setmac" command, correct?

Thanks to everyone who somehow tries to help me and sorry for my english!

TFTP recovery https://openwrt.org/toh/tp-link/tl-wdr4300_v1#flashing_via_tftp

Hi @frollic, how are you?

I tried to follow the procedure described in the link, I even managed to send the firmware to the router, but after that, nothing happens...

How did I do it?

  • I got a "factory" type Openwrt firmware;
  • I renamed it to "wdr4300v1_tp_recovery.bin" and placed it in the root of the TFTP server, in this case, I used "tftpd64.exe";
  • I set my network card to 10 megabits half-duplex and set the IP to;
  • Disable Windows 10 firewall;
  • Start tftpd64" as administrator;
  • I pressed the reset and kept it tight while I turn on the router;
  • After 1 or 2 seconds, tftp sends the firmware to the router and the progress bar goes to 100%;
    From the above procedure, nothing else happens. Even if I wait 2, 5 or 10 minutes nothing happens, so I try to power cycle the router and I still have the same corrupt firmware issues.

Where can I be wrong in the TFTP procedure?

The uboot can be picky about the file content/format.

You can always try to load the tp-link fw, just read up on the format, or you might brick it.
Some images needs to be stripped.

The WDR4300 device page contains some PCB photos.
Tx appears to be the square pad, and the Tx trace is on the bottom layer.
However, there are multiple device revisions and the board in the photos may differ from yours.

There is JTAG on JP1 (2x7 pads), but I cannot help with the flashing procedure.

Take a backup of the flash contents. With luck, the ART partition is still OK and could be reused when writing the new firmware.

1 Like

Yes it looks like the trace in question is on the bottom side, so look there to repair it. Should not be necessary to go more than a little way back from the damage.

Preheating the board with a hot air gun is needed to melt the ground pin.

If all the holes are open you can put pins in them and tilt to the side without solder to make a temporary connection.

On the technicality I would say it is the other way around. RHoS products without lead use lead free soldertin and that requires over 400°C and high energy transfer to melt. That temp only high quality “new” solder irons can reach. But the board is built for that temp!
This type of damage is more common with to cold solder iron (made for lead solder tin with melting temp below 300°) that actually don’t melt the solder (or takes to long to transfer energy) and with the combination of simple brute force trying to pull out the wire from the VIA and then the VIA comes along with the wire.