There is still something seriously amiss here. We have the same enlarger with same dichroic head and yet with a 10x8 B&W print my times are under 20 secs at f8 and this is with a 75W bulb and not the 100W that Durst recommends.
Originally Posted by Roger2000
Have you tried what Bob suggests? His test and mine are much of a muchness. Set the Y and M filters to any figure say 50and 50 units then swing them out of the way with the lever on the left or at the back if yours is a slightly older Durst 605 and any colour on the boards should instantly disappear and be replaced by bright white light. Then dial in Y and M as I suggested to check on the progressive change and finally do all three filters by the same amount together say 20 units at a time to see if it progressively darkens but with a neutral grey. All three filters together should give a grey look
That way you can eliminate any problems with the filters sticking.
I have never had a condenser head so can't compare but both B&W and Colour negs are very bright at f2.8. I use this for focusing but f4 is nearly as bright. It is true that at the aperture and with dual filtration for say grade 3 -3.5 correct for an exposure of say 10-15 secs the neg does then look gloomy but that doesn't matter as you have focused. What counts is the print.
However ignoring the darkness aspect of the projection your exposure times are still a complete mystery to me.