Fireflylite PL09 has black spots on LEDs. Maybe I should dedome?

So after about a month my PL09 Quad arrived. It has all the features I ordered, Red host, purple aux, and 5700k 519a emitters. Unfortunately, it looks like during the soldering process some crap got on two of the emitters. Am I right in thinking I can “solve” this problem by de-doming the emitters? I’ve never de-domed an emitter before. Can I do it while they are still inside the light?

Ouch, that’s quite a smudge.
Looks like it’s baked firmly on the dome, hopefully not burned in.
Try a cotton swab with windex (which is basically alcohol, water and soap) and if that doesn’t work try some naphta to see if it can be removed.
Try brake cleaner if that doesn’t work either.
Stronger stuff will possibly mess with the dome silicone.
Hope you can get it off without damage.
Otherwise it’ll have to be replaced or dedomed if that’s easy enough.

I see the LED next to it also has a little speck of something on the dome.

Man that’s really bad!! There’s flux spatter all over the place, not just on the emitter domes.

Yeah, try scrubbing it away…I use 91% isopropyl and some electronics scrubber things but q-tips will do. Might be hard to apply enough pressure without fudging those soft domes, but give it a shot. If it’s really burned onto the domes then there’s nothing you can do about it anymore. While scrubbing, if you lift one up then dedoming you will go…they’re not hard to lift so that may happen since heated flux is often a little labor intensive to remove. Sure, dedoming in the light is fine, and these are easy, just try not to let little bits get down into the holes in that board.

I probably wouldn’t use any petro solvents and such, but if you do, be sure to clean all those areas well afterwards with alcohol and let it air dry very thoroughly before sealing it all back up, because any residue will outgas/create vapors and most of those are harmful to LEDs.

I don’t know how dedomed would look behind the optic but I think a lot of people have shared theirs with Hank’s models here and on reddit. It’ll change for sure but smooth over a lot of sins.

I think I’d be asking Jack for a new board or refund/reorder on this one. That really is bad.

Naphta (lighter fluid) is harmless to domes.
Brake cleaner should be the last resort.
Acetone, car fuel and toluene and stuff like that is too agressive.
But it depends on the dome too.
Luminus LEDs have really tough domes.

It’s great if you can dedome them properly without heat or solvents.

Good luck sorting it out.

This just looks to me like a simple fix. The led that has a black mark is most likely flux from soldering, and similar to what I see on the rest of the board. The led dome is made of silicone is very unreactive to most things, so it should come off easily. I recommend using rubbing alcohol and a small brush to clean up the entire board. I recommend using high concentration like 91%, which will evaporate faster. This is commonly done for electronics so it looks like not a problem here. Just make sure the alcohol is fully dry before reassembly. My only comment is that this should be done by factory by default.

Update: I recommend use nothing else but alcohol (ethyl alcohol or isopropyl). This is what is used in labs for simple cleaning of board flux. The other organic solvents are too aggressive and may dissolve other things and some may be harder to evaporate. Also do not need to put too much alcohol because it does clean away some of the thermal paste under the mcpcb.

Looks similar to the 519A on my new(warranty)TS25. I de-domed it and found the burn was from the surface of the emitter. Lost some lumens but still builds light as it’s ramped.

Osram put out this whitepaper a few years back. Far more info and better info than anything I’d seen before, pretty comprehensive testing. Definitely depends on the dome material and polyester types are affected differently than silicones. I’ve seen what happened in Jeep aux lights that someone homebuilt and it was weird how the plasticky domes on his were discolored and crazed from solvents in the housing (pretty sure it was an auto paint lacquer thinner…which are mostly acetone but lots of other junk in them too). Some heat sink pastes and potting compounds are no bueno, too. Osram has a bunch of really good whitepapers, overlaps some with Cree but adds some additional interesting things as well.

Direct .pdf link: Osram Chemical Compatibility of LEDs - Product Document https://dammedia.osram.info/media/resource/hires/osram-dam-3813126/Chemical%20Compatibility%20of%20LEDs.pdf

SpeedB…wow, now that’s interesting. I wonder how that happened!

Yes sir, it is. Could there be a bad batch of 519A emitters. Are there flashlight gods and did I anger them, that’s 2 in a row.


The first one had a driver issue though, the charge indicator light under the switch would come on intermittently while not being charged. Faulty operation in general. Also it will go fire hot even on low output.

After a sloppy de-doming and cleaning out the sooty optic.

Y’know…it’s Nichia, so probably not, but anything is possible. Most of our budget manufacturers seem to get sloppy with the flux and/or don’t clean up flux or solder spatter before they ship lights out, and everything is still hand soldered - often these factories have a lot of turnover once or twice during the year, too, so the people with the irons aren’t always very experienced or knowledgeable about the big picture (solder looks good, it lights up, why bother with flux cleaning….). We know this emitter can handle a decent amount of current and heat pretty well, so I’d lean toward human mistakes in assembly.

Was the burning beneath the glass window or on top of it? Makes me wonder if an iron tip was pressed against it and lifted the edge so junk could get under there…or something.

Under the optic. Seems the dome burnt/erupted, flecking the underside of the optic. I’m no expert so I can’t tell if something was on the dome that got super heated or it came from the surface of the emitter and burnt upwards into the dome. Possibly a speck of dirt was on the surface of the emitter when the dome was applied?

Oh, I meant under the glass that is on the emitter itself, not the plastic optic. Below the dome is that glass, and then beneath the glass is the rest of the package with the phosphor and all that. That’s weird, though. May there not be any widespread defects and may you have better luck with future 519s. lol :slight_smile:

I don’t know if external debris could affect the phosphor under that glass, but from other emitters, yeah, we know it gets hot and can really damage the emitter. I was really surprised to see junk remaining on yours after you removed the dome.

Thank you Correllux. That shows how little I know. A glass window on top of the phosphor, need another look with a good magnifier.

Considering the very low Vf of 519A and very low DCIR of some 21700 cells I don’t think it’s very surprising that some would burn in direct drive.

Ah, direct drive…
The blue LED reminds me of the early days of the Astrolux S41.

Using a Samsung 40T. Shows 17 IR on the Miboxer charger. Never burnt an LED on any light before. Coincidentally, Wurkkos has asked which battery was used and said “maybe the battery current is too high”. Direct drive - so no throttling of amps through the driver to the LEDs could destroy them? Who knew, is that really possible, should there be a battery requirement disclaimer?

Either way the light is being used as is and there has been no further damage, so all is good.

I tried cleaning the really messed-up emitter with a moist lens cleaner wipe and I could feel an indent where the dark spot is. So my plan now is to de-dome. I’m nervous about it though because I don’t think I can remove the pcb from the device so I will need to reach in and do it.

Jeez, I hope mine doesn’t turn out like that! Based on the proximity of my blemish to the soldering though, I have a strong feeling I know where it came from.

This is the risk of direct drive fet drivers.
It’s one of the reasons i hate them.
There is no current regulation / limiting with these things.

Yes I agree. I think a few driver designers here like loneoceans have said before that they do not think direct drive is good idea because of this problem, but unfortunately most people in the community seems to want them because they produce big lumen numbers… and unfortunately people do choose flashlight on the specs which makes is challenge for manufacturers who want to sell flashlights… difficult to make everyone happy.