Have you checked the PRAM battery? There's no video on that machine if the PRAM batt is dead.

You'll need to get an adaptor. The Quadra 630 supports only 640x480, 800x600, and 832x624 video modes and does not support the portrait monitor.

This I find strange, since its predecessor, the Quadra 605 supported video resolution from 512x384 all the way up to 1152x870, plus the portrait display at 256grays on 1MB of VRAM. (Stock was 512MB but it was upgradeable to 1MB).