sorry for not noticing your kind reply Bick.
if you mean the knob at the bottom yes it is always leaking and i use it to adjust the pressure. i sent it for maintenance and the guy wants to charge me 50$ to change the piston and the bearings! i dont think it has anything to do with it, what do you think?
can i add a tank to it? does it solve the problem? do i need to pay for a regulator or maybe the old one already installed on it is usable . i dont have any ideas and paying 300$ for a TC620X is the last thing on my mind, please help.