What would cause this (burnt dome)

Fairly new p60 I put together can’t really think of a reason why the dome would burn like that. The light still works and get up to full brightness but after 3 seconds being on visible smoke starts pouring off the dome (that stinks like burnt plastic)

Its also only the one side on top of the dome. You can scrape it off the surface and the dome will be clear again but turn it on and it burns again.

Its got a 8* qlite driver

As well the smoke has left a nice film on one of my new AR coated lens. I’ve tried LCD cleaner with no success. Any ideas what would work good to get the film left behind gone without damaging the AR coating.

I’m no expert, but that neg lead isn’t looking to good. Have you tried powering it outside of the host to see what’s burning it up?

How does that screw into a P60 reflector with the wires taking up all that space?

You could try cleaning the lens with isopropanol.
This is 99% pure anhydrous (free from water) alcohol.
Works well on reflectors too if they are gently soaked then rinsed with distilled water.

As fishmaniac said, and although it’s hard to tell, that - contact doesn’t look very good. It looks like the lead is barely holding on to the solder pad. Maybe because of that it’s causing a higher resistance, creating heat there.

Have you tried re-soldering that contact point, and then clean off any flux before trying the light again?

I think you need to tidy up the negative solder joint. And take care to remove flux as said by others.
(Edit: Ohaya and I seem to have been typing at the same time - but he's clearly faster )

For the AR coated lens, how about some photographic lens cleaning fluid and lens tissue from a camera shop? Camera lenses are also AR coated. Use only gentle pressure.

I have had two domes do that. One was in a stock light and I didn’t see anything that made me think it was wired wrong and it sure wasn’t being overdriven in the light the way it was. The second one was on a build I did and still swear it wasn’t anything I did although I was pushing it really hard. I ended up cutting part of the dome off with a razor blade and in both cases it solved the problem without changing anything else. I actually thought that it might have been a defect in the dome itself.

That area’s probably glowing like a filament. And as Comfy mentioned regarding the reflector, maybe its shorting right where it touches.

Your dome is probably not burning but rather a victim of smoke/soot considering you can just wipe it off.

Sorry guys I meant to mention in my original post that the negative is not attached in the picture. I was starting to tear it down then thought I would take a picture before I had it all apart.

I’ve since put it all back together but it still starts smoking the dome within a couple seconds.

When I’m testing it Im not even putting the reflector on(just using test leads) but normally I use both the white centering ring then a insulating gasket over that so there is 0 chances of shorts.

It is definatly the dome that is burning it doesnt simply “wipe off” but you can crumble the black bits out easily but then there are chunks of the plastic missing. And like I said its only the top of the dome its about 1.5mm up from the substrate.(you think it would start at the base and work up the led not from the top down one side)

Sounds like a dedome might be your best option at this point.

The dome gets really hot, incredibly hot, when running. Hot enough that it will melt your skin onto it if you make the mistake of touching it after it's been on a while (don't ask how I know). If there was a dab of flux or something else on the dome it could have burned and created a defect, and then even after cleaned off the defect itself could have been enough to focus the heat and keep the burning going the next time it got hot. It will keep going until you get rid of that section of dome, a clean slice with a very sharp blade may be enough, though I'd soak it in gas and get rid of the whole compromised thing altogether.

If you have an old LED you don't care about and want to experiment, try this: make a small dot on the dome with a sharpie or other permanent marker and then run the LED at a reasonable current (~3 amps) and watch what happens. :O


Well I cut the dome off with a razor just under the burn line and tried lighting it up for a few min and everything went well. So I took everything apart again and left it in gas overnight to remove the rest of the dome. Just finished playing with it and seems that all is good. So looks like comfy’s theory was correct. I’m really not into throwers so i guess I’m gonna have to pick up a good throwing host for this guy. Any suggestions on what will accept a 16mm copper star?

This happened to me once. The oils from my fingers were left on the dome of my XP-G2. Once assembled and turned on the inside of the light filled up with smoke. Though It never burnt as bad as this, I cleaned the dome with alcohol and never had the problem again.

This would work:

I’d add this for a driver:


Edit - Just noticed the C8 has an OP reflector… :frowning: I’m not sure that’s the best choice for a dedomed thrower. Anyone else have a good suggestion?

Don’t be mad at me( I am not kidding you) but this looks really funny :slight_smile:

You remind me on my first soldering attempts.

From your picture nothing looks good.

- MCPCB + - contacts were not pre tined before soldering wires.

- Wires distance is not properly measured and cut.

- Wires are also not properly tinned.

Looks like emitter got to much current than needed and probably bad thermal path to pill done this job of silicone burning. So when you were running emitter all heat was concentrated in emitter and noctigon.

It can survive short thermal shocks but it will not survive extended ones.

This happened to me once. The oils from my fingers were left on the dome of my XP-G2. Once assembled and turned on the inside of the light filled up with smoke. Though It never burnt as bad as this, I cleaned the dome with alcohol and never had the problem again.

Maybe some flux splattered onto the dome when you were soldering the connections? I always use something to cover the dome.