5500 board won't POST/chime w/o the Display hooked up?

Trash80toG4

Active Tinkerer
Apr 1, 2022
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Bermuda Triangle, NC USA
I've got a test rig that'll boot Alchemy and Gazelle boards with no problems at all, but not my AIO 5500 sub-variant of Gazelle. Does it fail to POST due to lack of internal CRT hookup or might there be another issue with this particular board?

If display is indeed the problem, will it POST with the external display/projector cable installed in lieu of the checking for function of A/B CRT hookup during POST?