That is not correct. The A4000D will boot without keyboard, mouse or Zorro riser board. Obviously needs a working CPU board, both clock source jumpers set correctly (both INT for A3630, both EXT for nearly everything else).
Has it had battery corrosion? There's a few common problems that corrosion can cause with the RTC and fast memory interface which can stop it booting.
Remove the chip memory SIMM (nearest to the centre orf the board), you should get a screen screen at power on. If not, then you probably have issues with CPU board, ROM or some other hardware issue.
I think he means "a green screen"....
