Just toasted an XHP70... How can I avoid doing it again?

So… I finally found a use for my DST. I ordered a 5500k XHP70, carefully sliced the dome down and lightly sanded it to give a frosted effect to eliminate the XHP “donut”. I built a FET+1 driver with a zener mod, assembled everything, fired it up with some half-charged Samsung 20R’s and… immediately started giggling. It was so bright! Within about 20 seconds though it started turning green and holes appearing in the hotspot. Oh no! I immediately assumed I had melted the DST’s plastic reflector. I opened it up, and this is what I found.

Somehow my precious reflector (mostly) escaped without damage, but what happened? I’ve ruined emitters before but not in such a spectacular manner. I have a spare XHP70, but how do I avoid this happening again?

It looks like the dome material burned. Did that light frosted effect trap light/heat? Or did just everything go poof from all that wattage? Have you identified all the burned/melted materials. It does look well heat sinked. I’ve actually warped a diffuser from heat that I placed too close on a triple build P60.

The frosted finish is the only thing I can think of, but I swear I’d seen people talking about doing it with no ill effects. It actually still works, still gives off light under all that mess.

I’m going to assume it was my dome treatment since it still lights up. Y’all think I would be safe slicing it, just leave out the sanding?

this video has some good info

Maybe some sand particles got trapped inside the shaved dome and burned…

At this point, the emitter is already toast. Maybe break out a fresh x-acto knife blade and try shaving off what is left. Then give it a go without the sanding.

Yucky. Can you take a tailcap reading of the current draw?

You, Sir, give tremendous advice. Here is the exact same emitter after a new slice and alcohol bath.

Mighty purdy looking under there.

I did a scuff job to an XHP 50 and it diminished the cross but having heard about this same thing happening to dirty domes ended up slicing instead.

good to hear that it worked again

pilotdog68 after slicing the XHP-70 did it get warmer than 5500K ? like the 1A XM-L2 gets much warmer after dedoming ?

Oh yeah, that was one hot dome!

Place a piece of white paper in front of an XM-L2 at a few amps. Bring the paper to touch the dome if you don’t care much about the dome. The paper will burn. There are concentrations of energy greater than some powerful lasers at the dome. Always use a filter away from the LED. Creating one near it is going to drop lumens and maximize heat at the die, as seen here.

It warmed up some, not as much as a full dedome would though.

So the domes on these are hard to remove?

what is the safest method of dedoming these?

beautiful! :heart_eyes:

how did you do that?
razorblade?

No tools were used at all.

A dome was never touched.

The heatsink weighs 120g and is shown in the photo.

Tint shift = 0

So how did I do it?

:bigsmile:

you ran it until the dome melted ?
or had you still to push it a bit?

heatsink seems to be a piece of wood
(not szre what you needed the capton for)

did i win one of your shiny wonder thingies? :smiley:

The kapton is simply to prevent hand oil from contacting the exposed copper, which would cause oxidation before use.

I wouldn’t use a piece of wood as a heatsink.

Tint shift = 0

You’ll have to think clearly and do better than that.

:bigsmile: