A Beseler CB-7 enlarger has what is called 'condenser counterbalance springs' connected to the casting above the negative platform and the bellows that connects the top casting to a lower plate atop the negative. The casting is free to move up and down on the top of the focus rail. And there are some springs up there, too. So it is sort of bouncy without a heavy condenser there.

I'm reconfiguring the light source. The condenser has been removed and the replacement is a relatively light weight LED lightsource. I have the upper bellows nearly fully compressed and the upper condenser casting I'd like to stay put at the highest point. There are a couple of thumbscrews that ride in slots that look as though they could secure the casting, but when tightened fully, the casting is still free to move on the springs.

Is there some knob or rusty adjustment I've missed that can lock the upper casting into position? For now, I've added a C-clamp.

I've reviewed the owner's manual, but it doesn't seem as though this is covered.

Thank you. -ejw-