I did your test, azdave. I rewired the loose red/black wire thats grounded to the chasis, to the cigerette lighter light bulb. Turn my marker/parking lights on. Low behold, everything lights up and its very bright also my headlights are too.
If its ok I taped red/black wire to the black and yellow bulb wire, with electrical taped.

Everything turns off and in as it should
But, now the round dimmer switch can't adjust the dash gauge lights.
Time to trace the lost connection to the dimmer control.

My brother did look under the dimmer control, messed with something not sure what. But the chime when I turn the key on doesn't chime.