Hey everyone, first time poster here 
I'm unable to reinstall the original Zyxel Firmware on my NWA50AX Pro. The device does not seem to scan for TFTP servers and i cannot connect via TTL as well.
Any help is greatly appreciated.
What makes you think it's supposed to scan.... for anything.
I've read that this is the behaviour on bootup - it would look for a TFTP server at a specific adress. It does, however, not do that.
That's why I tried to use Serial Console via USB, but to no avail as of yet.
Post the serial output...
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There is none 
I am using the following adaptor: Waveshare Industrial USB to TTL (D) Serial Cable, FT232RNL Chip
I run Putty on Win10, select the COM2 (which is assigned to the adaptor in Windows device manager) and set the baud rate to 115200
-> Nothing in the console. I did a loopback test and that worked. I also get some noise/symbols from plugging/unplugging the serial cable on the AP side.
Then it's not really scanning anything, is it ?
First thing to try is to swap is Rx and Tx.
I did that about 11 times by now.
What exactly did you connect and how? You only need Rx, Tx and GND. Do NOT connect 3V3.
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I connected as follows:
AP Pin 1 = not connected
AP Pin 2 = connected to Adaptor RX
AP Pin 3 = connected to Adaptor TX
AP Pin 4 = connected to Adaptor GND
Switching Pins 2 and 3 does not change anything.
GND should be closest to the RJ45, then Rx and Tx.
https://www.reddit.com/r/hardwarehacking/comments/1kpndw7/uart_pinout_on_ap/
There are some useful Zyxel recovery links in NWA50AX Pro installation failed.
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Damn mate, I figured GND was the one marked with a little printed triangle! Thx a lot.
Seeing stuff on the console now and will try to complete the next steps on my own.
I will report back later, thanks to everyone for all the input so far!
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"assumption is the mother of all fuckups..."
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