Troubleshoot 4.0

Hi Tesi! well if you have 4.46V at the 2.5V test point the virtual ground of the input stage would be wrong and it wont work
Check:

• Resistors R7 and R8 are likely to be wrong, maybe you placed different values?
• In the image below, make sure that you have the same resistors and voltages
• Make absolutely sure that you have the resistors showed below clean and without shorts, or dry joints (re-solder the joints again!)

Keep us updated with your progress!

the problem was the resistor R7, now it works!!!

good!!

I still have lot of noise, what about using a power supply with 9V and 1300mA OUTPUT?

Have a look at this (it is for the DUE but essentially you can apply it to the UNO):
www.electrosmash.com/forum/hardware-peda...powering-arduino-due

Regarding your 9V and 1300mA OUTPUT, every power supply is different, some 9V are switch mode power supplies that are pretty noisy.