Hello guys, my router (TL-WR941ND) got bricked during reverting back to original firmware.
I couldn't do failsafe, nor use the holding reset button method to unbrick it.
So I put together a usb to serial cable using old nokia 3.3v cable laying around.
couldn't get any output using it at all.
after putting it back together, now it doesn't turn or power on at all, unless I hook the serial cable to it again, that is when i see the LEDs flashing and lighting up...
what can I do now ?
You may have to connect the uart cable (at least tx) after powering up the router (just a second later), as current from your tx pin might partially power up the SOC and put it into an uninitialzed state.
If that doesn't help, TP-Link in all their wisdom, might have removed some crucial components (usually 0-ohm SMD resistors) in the rx/ tx path(s), as they like to do on recent devices.
I am not sure what you are refering to... I am not really very experienced with this... but the router doesn't power up at all using the adaptor.
If I wanna see some leds lighting up i have to hook the serial cable.
that is what I mean.
In that case, with the serial console disconnected, either the PSU is shot or you broke the PCB while soldering.
I didn't really solder it, i hooked the wires steadily just to try if it is even going to work. 
Did you oconnect VCC when you first tried the serial connection?
If yes, the probability is high that you damaged something on the board.
I only connected, the 3.3v, ground, TX, RX
Get a decent serial cable and follow the tutorials in these videos...
Part 1 -
Part 2 -
Works for other routers as well.
Hello
I have done many times this procedure with differents routers, and never conect VCC, only GND, TX and RX. VCC came from the board when you turn on. If you don't see anything on console, change TX and RX and try again.
ok but how can I turn it on now without the VCC ?
If you turn on the router with its power adapter, you don't need VCC from "Serial to TTL converter".
check your solder connections for bridging. if there isnt any you probably fried it with that cable.
Guys I didn't solder anything. and the router doesn't turn on with the power adaptor.
the only way I get it to turn on and see the leds lighting up, is by connecting the vac to it.
I hope I cleared up the confusion. and the cable i used is 3.3v not the 5v one
Then probably you fried mobo, look for some open resistance
check for voltage on the ps. if its working its fried
How could it be fried if it still turns on with the vac ?
sorry I am not very knowledgeable about this
the 3.3 leg on the serial port just energizes a portion of the circuit thats why it appears to be on
That's correct, if you put voltage on the motherboard, the LEDs can light
oh 
so it is too late now to fix it ?
do you think connecting the vac plus the power adaptor can cause this ?
also, when I power it with the vac, i get the same pattern on the leds lightings as before this happened.
like flashing the same way. like that blink pattern when it is in a bootloop
In that case, look for an open fuse, or a resistor, or coil.