Sounds like there is no GND (0V) connection to the Regulator.
Try doing a continuity check from the power socket to the middle pin/metal tab of the regulator, if you get a reading of Zero or only a few ohms it is probably OK and the problem lies elsewhere, if you get a high or infinite resistance reading you will have to trace where the problem is. A bad solder joint on the regulators GND pad or crack between the regulator GND pad and the GND track would be the first places I would look, if it is not there then either check the continuity of the GND track from the power socket to the regulator a few inches at a time until you find the break or solder a piece of wire from the power socket to the regualtor.
I checked and found that there isn't any connection between bottom and top layers at the jack power connector, maybe the via is corroded.
So I installed a new power connector with two wires soldered both on top and bottom pads of the pcb, and it works perfectly
Thank you very much!
Edited by tr0x, Mon Dec 10, 2018 8:48 AM.