I've taken out the diffuser from the drawer yeah. The bulb is fine and is brand new, and the one recommended in the manual. I haven't checked the voltage yet cause don't have a multimeter here (I'll do this though) but the naked bulb seems really bright. There's a heap of light there. The mixing chamber is definitely an issue cause it looks terrible inside, and when you look at the light bouncing off it, it's distinctly yellow. I found a thread somewhere (I can't find it now unfortunately) where people were talking about the same issue with the mixing chamber degrading so it's a common issue by the looks of it. I really want to try fix it up a bit. I just don't really know what type of paint will be suitable.
I have two lenses a schneider 75mm and a moepta anaret-s 50mm and it's really slow with both. The meopta has a little bit of fungus but not bad, and the schneider is clean as a whistle.