I recently acquired a used micromatic premium nitrogen regulator and the title says what my problem is. With no cylinder attached and no pressure, the low pressure (beer gas line) gauge reads 5 psi. I removed the plastic cover and pushed the needle down to zero, and it promptly returns to 5psi. Is there a way to calibrate or adjust these things? I read the manual, no mention of this problem. I would rather not have to buy a new gauge, but I will if I have to. Just wanted to see if anyone could assist. Thanks in advance!