With Nino on this one, the strobing is most likley a bad connection on J1 on the CPU board. Maybe the pins are corroded (sand them lightly with sandpaper).  I have had this problem before and it was connector related.

The GI could be a connection on the backbox wiring  itself check if any of the wiring that loops from lamp to lamp (steel braid) has come away or is broken in any way.