Once the color head is installed, it is bolted to the body with brackets and the adjuster knob is removed. If you have the knob and wish to revert to the condensor head, remove the two small brackets on the sides of the enlarger that afix the dichro head and lift it off. This will free the upper bellows to move, then set the condensor head on top and plug in. Oh yes, remove the diffuser from the filter drawer.