That would be your analog board on its way out. 
My Classic II started doing that, then it would be:
- Turn on
- Fan comes on
- Mac boots
- HD comes on
- video comes up but is dark
- video finally really comes up
After a few months, it would get to the point where it would take a full 15 minutes to boot. After that the analog board let out the magic smoke. :'(
RIP: Classic II (1992 - 2006)
When your analog board goes out, find a Classic or Classic II with a good case front, analog board, CRT, and strip it to just that, and add your drives, mobo and if you want, case bucket. Shouldn't be too hard to find.
My Classic II started doing that, then it would be:- Turn on
- Fan comes on
- Mac boots
- HD comes on
- video comes up but is dark
- video finally really comes up
After a few months, it would get to the point where it would take a full 15 minutes to boot. After that the analog board let out the magic smoke. :'(
RIP: Classic II (1992 - 2006)
When your analog board goes out, find a Classic or Classic II with a good case front, analog board, CRT, and strip it to just that, and add your drives, mobo and if you want, case bucket. Shouldn't be too hard to find.