Question about loop back test

Hey, When i type data in the serial monitor I see only the RX LED blink but not the TX LED Do you have any idea what the problem could be ?? i would appreciate any help

You have D0 and D1 connected, with Reset grounded?

yes the D0 and the D1 are connected together and the Reset pin is connected to the ground

Did you try changing the USB cable? They are flexible wire & do break occasionally.

Does it do the same if you remove the 328P chip from the board (on the Uno?)?

Do any chips on the board feel warm?

May come down to the USB/Serial chip got zapped somehow. You can try reloading it.

Yes about the cip getting warm My board is an Arduino Rev3 and the chip right next to the TX and RX LEDs gets really warm .

It's dead then. It should not be warm at all. The only thing that should feel at all warm is the 5V regulator.

I changed the USB cable and yet nothing changed I also tried the same without the 328p chip and it's the same result

Dead 16U2 then. Unless you have SMD replacement capability, you are out of luck.
You should be able to use an FTDI Basic and connect to +5, Gnd, DTR thru a 0.1uF cap to Reset, and Tx/Rx connected to D0/D1 (or D1/D0) and get serial comm’s back that way.

Then you mean that the arduino is dead? and what solutions do you think would work ? Could you plz use more simple words , I'm new in arduino .

Well, it appears the USB/Serial interface chip is dead, the small square one. I don't know about the Atmega328P, the large DIP part. You can get a bootloaded '328 and an FTDI Basic https://www.sparkfun.com/products/10524 https://www.sparkfun.com/products/9716

Replace the chip, connect the FTDI Basic as I discussed earlier, and see if that will get you back in business. Do you have a voltmeter? You could also check to if 5V and 3.3V are still okay on the board, or if you managed to take out the regulators also. In which case, get a new board and be more careful next time.

This place often has slightly older hardware that will do just fine, such as http://www.nkcelectronics.com/arduino-duemilanove.html I still use my Duemilanove for checking out stuff, and I use FTDI chips for my '328P & '1284P designs.

Do you know what did i do wrong ? So i i'll be careful next time

Shorted something to something, I don't what you had going on. The 2-3 chips I zapped on promini's all got brushed with a 12V supply line, killed 'm nice & quick! My boards use FTDI chip, never had one of those die.