Light bulb voltages

[MacGeek]

I have come across a collection of new, unmarked low voltage incandescent light bulbs, both bayonet and screw in types.  These might be used in vintage audio gear to light front panels, among other things.  They are not flashlight bulbs.

Does anyone know if/how I can measure the operating voltage range.  I tried measuring resistance, but they are all the same and I doubt that is actually the case.

Thanks for any help

MG

[gdv]

Mac,
Guessing you know they are all dc bulbs?

[MacGeek]

I have similar, marked bulbs-A/C or D/C (never knew it to matter)

[ataudio]

You could hook them to 1.5v D cells and keep adding cells until you feel they are at thier appropriate operating brightness. I suspect you could start with 6vdc and increase from there  Without any markings it could be hard to tell.  If you have a 12vac center tapped transformer you could test with with 6.3vac and them 12vac.

[MacGeek]

Thanks for the input.  I have used a train transformer (A/C) with a volt meter looped in with some success.  I am hoping there is a more reliable approach due to a concern that what might look safe in the short run may cause premature bulb failure over time if the voltage is too high..