So, I've got this old beseler 23 with an aristo cold light head in it. Everything seems to be working well, except the annoying fact that the illumination is way wonky. I've been a contact printer for ten years, and haven't been enlarging for very long at all, so all of this is pretty mind boggling. Burning in the edges/corners of a negative seems pretty straight forward, but I am getting a triangular shaped falloff that starts pretty far into the negative. What I am asking here is, how to minimize this and diagnose where the problem is coming from. I'm using a schneider 80mm lens, enlarging 6x6 and I have the light source as close to the negative as possible. Would a change in lens make a difference, and if so what are good options. This is a really old enlarger, so chucking it is also an option. Maybe you are supposed to lose ~2 stops of light from the center to the edge of the image? Cheers and thanks for reading my ramble!