I have the same enlarger as you. I am making some assumptions here: Your negative is 6x6, right? And you didn't crop much to get the 7x7 print shown here? In that case, your exposure time sounds plausible for the given enlarger and light source, if the negative is on the very thin side. 7x7 is a very small enlargement from 120 film, only about 3X. I'll reiterate what others have said: Develop the paper fully but lower the exposure, either through setting it still shorter, stopping the lens further down, putting in a ND filter or a combination of those. A more extreme approach is to intensify the negative, but I cannot give much advice on that, since I rarely if ever need to do it.
Originally Posted by teekoh
If your negative is too thin, then you have to figure out whether your exposure or development went wrong. There is a multitude of reasons why this could be the case, and merely following prescriptions is not always a guarantee that you will get a good negative. It is easier to determine the cause if there is a constant bias somewhere. Sporadic inconsistency is much harder to deal with. Getting the negative right is where I would start if I were you, but of course that won't rescue this particular image.
My exposure times from 120 for similar paper etc are around 16 to 32 secs at f16, using Ilford MG filters. I almost never have to go to grade 4 or above, and for the most part I am around grade 2 or 2.5 for the base exposure. I sometimes use the extreme grades for additional burning in, but I am not very good at it yet. So in short, I don't think you can blame the enlarger. It seems the negative is the problem, if other possibilities such as fogging can be eliminated. For the sake of comparison, what are your exposure times normally? (For the same negative size and degree of enlargement, of course). Under- or over-development or exposure can have a marked impact on print exposure time, more so than you would guess with the naked eye, and more the higher the contrast you print at. I once had TMax 400 completely over-developed in caffenol, and ended up with negatives that needed 2 minutes exposure or more, at grade 1 or thereabouts. The amazing thing is that one can get a print from a way too dense or thin negative if you know how to work with it. Still, life is easier if you get good and consistent density in your negatives.