Hello and welcome. I have a Pinnock Sewmatic (they are brilliant machines and were made in South Australia). You will find a screw on the bobbin casing, adjustment of that screw will correct your tension (with much practising on a scrap of material). Any other questions pm me. Can't promise a very quick reply as have some family dramas happening (I come here for therapy, when I'm not quilting!).:)
This is my "Jasper"