Looks like I'm fixed.
I'll meet you halfway here, Phil. My best hallucination is, the monitors do indeed get their power via the S-video cable. There is no other apparent power source to them.
Your suggestion that I'd blown a fuse didn't make sense at first because the DVD is working. Bad logic on my part.
The small harness that plugs into the available white/square connector above has three wires -- one each red, yellow, black. What if one powers the DVD, the other the monitors?
Chased the wire harness from back to front and found it terminates in the black plug in the top left of the below picture. Pulled that plug, checked continuity on all three -- one open. An in-line fuse is the culprit.
I'll put it all back together in the morning and with any luck, this problem is history. Thanks as always for your help, Phil.
