Hi esteemed group,

Has anyone come across an A19 E26 base LED (standard screw in lightbulb type) that will work in both 120 VAC and 74 VDC. These would be used in Amtrak Heritage electrical systems. There are a number of electrical fixtures that are powered by 120 VAC. But when power is removed, a relay changes state and teh fixtures are powered by the battery system.

Thanks,

Dale Grice

LED bulbs have built-in voltage regulators that knock the voltage down to what the LEDs actually use. If the supply voltage drops to low, depending on the bulb design, the regulator either will not supply voltage or sometimes will flash.

Try a 120v bulb and see what happens. You can’t hurt anything except for the possibility of the LED regulator not handling the voltage spike when switching back to 120v.

Maybe someone here has tried it and can offer more info.

We have 120 volt 100 watt equivalent, LED bulbs in the engine room of the F-3's with good results. They stay on full brightness with the diesel's 74 volt system. They do go completly out when the starter circuit is energized but come right back on once the prime mover is running.

Hi Bruce,
Do you remember or can you look up manufacturer and part #?
I'd appreciate it.
Dale

Just as a FYI, be very careful to watch the heat-sinking on nominal "120V" LED bulb assemblies being operated on substantial undervoltage. They may require additional cooling to have anticipated life.

LEDs are current controlled devices so as voltage and current are related, the regulator (driver is actually the correct term) would conceivably require more current due to the voltage drop and generate more heat. Nobody seems to publish minimum voltage data for LED bulbs and there is a threshold voltage in order to function but what might that be? Dunno. Depends on the design of the driver. I did read that some global manufacturers design for 95v to 230v AC to cover both US and Europe. Apparently that’s not so for all manufacturers. Hence, my suggestion to experiment.

I had sent the request on LED bulbs to a friend who owns Rail cars. His reply follows:

"Some brands work - others don't - but I might be thinking about cfl on DC - the cfl ones I found that did work - were maybe 10% of what I have randomly don't have any id on them. BUT I think everything I own has separate 75vdc bulbs for emergency light circuit with both voltage bulbs in same fixture most often emergency light bulb is the 6S6 (which comes in several voltages 75-120-130)

I think matter of try it - it won't hurt anything"

Good luck.

Harry Nicholls
Dallas, TX