Ah Jeff, we may have something here. If I use a 9v power supply, then the bulbs that come with the vintages (vintage bulbs) which I believe are 10v would still work. Yet I can replace the ones that burn out with 7.5v ones. hmmmmmm

If I build my operator board as I've designed in another post to use a 9v and 7.5v bulbs, then I could slowly convert all my machines over to 7.5v bulbs with out having to replace them enmass, which is what I'm trying to avoid.

I would have already switch to 7.5v bulbs, but I couldn't find a 7.5v 'wall wart' only 9v. Hmmm... I may need to experiment with this recommendation.