Thanks very much for that thorough explanation.
I tested each bulb individually with a 'C' cell that registered 1.6V on the voltmeter. No light from any, so it looks like I need to refresh the bulbs.
Now to research how to do that without damaging the housings.
It occurs to me that I may have tested the low voltage drops on the board with 'AC' selected.
That my be why I saw zero voltage from the board.
Thanks again for sharing your knowledge.