I posted this over on the LFPF this morning but haven't gotten a response yet so thought I'd try here. sometimes the focus knob on my 4550 XLG won't stay where it is positioned for sharp focus. Gravity starts working on it and the lens creeps downward. Any users of this enlarger encountered this before and if so, how did you fix it? I'm looking for a set screw or something that may need tightening but I don't see one........thanks.
