I want to turn this into a red only LED headlamp how would I go about replacing this XP-L HD to a red LED? Can I just re-flow A red LED directly onto the MCPCB or do I have to switch out the driver and such? And if I can just switch it out what are some red 35x35 LEDS for an XP board?
Gotta be careful, especially if using linear regulators like 7135s (dunno anything about the H40), as red LEDs only drop 2V or less, vs 3.something for white LEDs, and the 7135s would have to soak up all that excess.
Other than that, yeah, red XP-Es are easy to find, a bit less so if you want deeper “photo red”.
I just bought some red XP-E2 leds, I got a single led on a 20mm star and a 3 up on a 20mm star, how would I go about driving those as I have never worked with these kinds of leds before?
Cheap drivers just use a bunch of parallelled resistors to act as a ballast, but that’s not regulating anything, as current/brightness will decrease as cell voltage decreases.
Boost drivers (from alkaleaks/NiMH) don’t care, and just supply whatever they can to the LED. A decent 800mA boost driver is sold at FT.
Ah, here we go… https://www.fasttech.com/product/1127407-12-aaaaa-5-mode-800ma-linear-booster-led-flashligh
I haven’t used any Red XPE LEDs but have fooled with a bunch of green —-generally no problem if you stay 1.8 amp or less —I’ve modded several small lights with the stock drivers 1 amp or so —plenty bright for hunters to get to stands and night vision — I’ve done a few with 5/7135 chips kind of diminishing returns after 4/7135 chips—they’re still going strong for a few yrs now—-the thing it is with hunters most of the time lower modes work fine
Yes they replace xpl/nichia etc directly
The H40 is a single AA headlamp with ramping, so already has a decent boost driver 
(In other words, i think it’s already setup pretty much as Lightbringer is suggesting it should be.)
Should just be a straight LED swap, can’t see any 3535 LED failing to cope with a single AA NiMH maxed out, especially an XP-E2. A white XP-E2 would definitely cope with a 14500 Li-ion too, don’t know enough about the red version to be able to say the same, but it’s possible.
The H40 is set up for a single LED because the LED wires are routed to the outside of the shelf to match the cutouts on a single LED board, the LED wires for the triple set up would need to come through the middle of the board and hence the middle of the shelf, so you’d need to drill into middle of the shelf and re-route the wires. You’d also need to find a triple optic that fits. Waaay too much hassle for minimal gain.
Maybe slightly off topic but why would one select deep photo red instead of just red (or visa versa)?
No idea. “Regular red” is more on the orangey side (Portland orange, a/k/a traffic red) which is why newer red lasers are brighter to see even though they’d have the same mW ratings. Old old old red lasers were in fact deep red. (Still got one that I bought from Edmund Scientific æons ago.).
Deeper is said to not ruin your night vision as much, but it seems to me you’d just have to crank it up brighter for the same viewability as dimmer regular-red.
Maybe there’s something to it, dunno. I’m not terribly picky about monochromatic red.