Hi, just setting up my K40 and the current regulation knob seems to just spin freely, slightly catching at a different place each spin. Is this normal? How do I know how where it is meant to be?
Sounds like a loose knob screw
It may have loosened up on you during shipping.
if you look closely the center of the knob ( the hub of the knob) it has a cap… You should be able to easily pull it off.
Under that cap is a small nut that can be used to tighten the collet that holds the knob onto the shaft.
As to “where it’s meant to be” - there’s no “right” place to set it. You’re going to want to do some test cuts to match the pointer to the ma gauge. I used a sharpie to put some tuck marks for 0 (where it’s just about to lase), 10/20/30/50/75/100% power using 20ma as 100%. You can push it higher but that’ll shorten tube life.
Other people have made nice labels but I didn’t bother.
OK thanks, I can live with that, manually calibrated using a sharpie for the moment. As long as I push it gently back to both marks I know roughly where it is, tightening the nut hasn’t helped so far but I am moving on to the next (bigger) problem.
If the nut is secure there may be damage to the potentiometer.