We have located supplies of incandescent 25 watt 32 volt medium base bulbs like that found here.
http://www.bulbspro.com/symban-25w-a19- ... e-32v.html
Problem is still lifetime, at 1000 hours (2 or 3 months) with as many bulbs as we have we are constantly replacing them.
We have been looking around for 32/34 VDC LED bulbs for use within several cars on display at the IRM. I noticed more LEDs on the market since last year, some from marine suppliers. As most are around $20 each we wanted to ask around to see if anyone else has tried LED 32 volt bulbs, what they thought of them, or found others at a lower cost.

Warm white (3000K) from marinebeam for around $20
http://store.marinebeam.com/32v-led-lights-1/

The 7 watt warm white here looks like what we need for larger fixtures but at $28 a shot I thought I'd see if anyone else has tried them.
http://www.led-cfl-lighthouse.com/page/428093642

Thanks, Buzz

I don't suppose anyone offers bulbs rated at 34V. Seems like a trivial difference but I doubt there is any usage at 34V so if the hypothetical ideal voltage for this filament is 34V then running on 32V should produce longer life. Similar to those ordinary bulbs rated at 130V but typically used at 120V. BTW, 34/32 has the same relationship as running a bulb rated at 127.5V on 120V.

The mechanics at the local G&W short line have told me that they have been using the cheap Home Depot led bulbs in the cab and engine compartment of their gp and sw EMDs. I have been wanting to try them in our 50ton, but since that conversation, I have not had an incandescent burn out (and I have ten thousand more important projects).

The LED bulbs that railroads use... they will illuminate on voltage from 24 up to 74 VAC or VDC... either one. This is one whose light spreads out horizontally.. for number boards and at floor level use normally...

I quit testing at 74volts. I've plugged them into 115vac... they blink on, then extinguish. Doesn't do any damage...

Light output is bright no matter what the voltage... they don't dim down at 24. They draw very little current.

I run some on a 24vac doorbell transformer.... about 20 of them on one transformer right now.

I have no doubt they are expensive. An acquaintance of mine got a whole case of them from a source... and has put them up all over his shop.
I gave him a 74vac Tx from an old RR radio base station and he's wired all of them to it.
You can just run lite gauge speaker wire to them... low current draw and low voltage, too.

It's easier than that. Those common 12V LEDs intended for RV use? Many of them are rated for 12V-24V (i.e. 14.4-28.8v) and most will happily run on 32v. So try some.

How can they run on multiple voltages? Inherently, LEDs are constant-current devices. You can limit current with a resistor, but really, for best performance you want an active current-limiting circuit. That's easy to combine with a "buck converter" that accepts a wide range of input voltages. So that's how most are made.

A buck converter will stubbornly draw a fixed WATTAGE. Double the voltage, current will halve. Even on the fly - put it on a bench power supply and twiddle the voltage knob, the light will stay on solid - but current will vary in proportion.

What limits maximum voltage? Insulation within the device. Insulation is pretty cheap, every part is insulated fairly high (except for large electrolytic capacitors) because it's very easy to do so. You could physically tear down a device and look. But I expect a device rated for 12-24v (and thus, necessarily, containing a buck converter) should be good for 32v, 36v or more.

Here's one. http://amzn.to/1LdLCNZ

Here's one with an exceptional range. (yet still works on 12v) http://amzn.to/1KbNfM7

Look around, you'll find loads of em.

Bob, there will be a limit to the input voltage, depending on how the designer chose the inductor value based on minimum and maximum duty cycles for the (typically) MOSFET active switch.