Help, I'm new to quilting & I am entirely self-taught. I accidentally pushed the "tension knob" on my 21 year-old Kenmore... the instruction booklet doesn't say how to reverse this, and my tension is all messed up. It's not the 'numbered' tension knob, but rather a button on top (which made a serious 'thunk' when I pressed it down.) Any ideas anyone? Any suggestions would be greatly appreciated. Thanks!