Luminus SFT40 test

I reflowed my FT03 with an SFT40 and I think I have a new favorite LED. Current measures 9.63 amps with the HLY cell that came with the light, so I probably wouldn’t put a higher current cell in it. I dont have any way to measure the intensity so I can’t give any numbers on that but it looks impressive.

Lurker turned into a new poster here. I live in China and I just got a 4x SFT40 Jin Heng JKK80 light. The light runs on 3x 18650 and the seller claims 28A max current draw.

Small black dots have already appeared on top and bottom emitters while a bigger black dot is on the right one. The left one so far looks perfect.

While unfortunate, because it is a 4 emitter flashlight, there is nothing I can see in the beam. I’m just wondering if the emitters will stay this way or get worse? I ran it on turbo a few more times after the black dots appeared (2 minutes at at time for about half a dozen times) but the black dots don’t seem to be expanding or increasing in number. I can live with the black dots as long as the emitters don’t get worse.

Not sure, but may be a contaminant or particles causing the black dots. Hope it's not the high amps.

On Ali, this JKK80 claims SST40.2 LED's, interesting. I haven't seen/heard of SST40.2's yet, because we are pretty sure the SFT-40 is a domeless SST-40 new (2nd) generation part.

Did you get a "blue" output on max/turbo? If so, it could have damaged the LED's. I'd be surprised if a stock 3 cell/4 LED light this could happen but it's possible I suppose. Are the springs doubled up or bypassed, or better than average quality?

I wonder if it’s from left over flux or other contaminate that wasn’t cleaned off. Someone else posted about this in the Convoy thread

Tom E - You bet me to it

Have you heard of SST-40.2's yet?

Fairly certain that’s just the same that’s currently being used. The gen 1 were burning the bond wires at 8.5A, but no reports of this happening in the Astrolux FT03 with bypasses at over 9A. I was told a couple years ago that the FT03 was using the gen 2

Ohhh, true - could be right there. From the pic on Ali, it does look like a standard SST-40 we all know now. A domed SFT-40 would have the same bond wires as the SFT-40 I'd assume.

Thanks guys, no blue output - hopefully it’s just contaminants. I’m a little reluctant to open it up again since the flashlight originally had XHP 50.2 emitters but I decapitated them and took off all the phosphor with it.

I live in Shenzhen and I sent it back and the seller Old Jiang (the guy’s name and owner of Jin Heng) replaced my board with 4x SFT40s for 98 yuan.

So I guess it’s bad news… I took it apart and used some compressed air on the leds. It seems like the black spots are from the emitter itself (see the clearer picture below). I actually don’t think the emitters were overdriven much but don’t have a great way to test. They should have received 7amps at the most while SFT40s are rated for 6amps.

The SFT40s should be from a quite new batch since Old Jiang from Jin Heng just had them restocked. Do you guys think it will get worse? I ran it for a few more times on turbo today without more damage. Although my batteries are no longer fully charged.

you have to clean with cotton buds and isopropyl alcohol, pressing hard without fear. Before mounting the reflector, look at the LEDs with a magnifying glass to make sure that there is no trace of anything left.

I’m afraid of damaging the phosphor layer. I also don’t know what I’d be actually removing since I’m 90% sure the black spots were not there before running turbo. Anyone else try Paco’s method?

Had some flux left on the LED which caused a burn mark, used a microfiber cloth and scratched away at it, worked without any issues afterwards.

I’m afraid of damaging the phosphor layer. I also don’t know what I’d be actually removing since I’m 90% sure the black spots were not there before running turbo. Anyone else try Paco’s method?

the match has a nice silicone coating on top even though it may not look like it

Got it, I’ll give it a while and try to clean it eventually. The Jin Heng flashlight boss also said that it should be no problem. I’ve never seen black spots before even with other flat emitters like Osrams or XP-L Hi. Perhaps the SFT40 surface doesn’t repel flux splatter as well as other emitters? It seems too coincidental that others have seen black spots as well on this emitter more than any others.

The black spots will definitely get worse and will destroy the LED if run hard.

It can be caused by flux splatter or other debris. It gets hot from absorbing light and burns and chars which causes it to absorb even more light. If it continues it starts to burn the silicone then down to the phosphor. If the black spot doesn’t wipe off you can try digging it out with a fine tipped razor blade. Then wipe it down with alcohol. You want to remove all visible traces of the black stuff. I wouldn’t worry too much about damaging the phosphor because the LED is basically killed if you do nothing, anyway.

It’s a little surprising that it’s happening on 3 out of the 4 emitters. Could be a lot of flux splatter. If the thermal dissipation is very bad and the LEDs get very hot that can also increase the likelihood of phosphor burning.

I did the same mod (as i think eve talked about), switching the sst40 in ft03 for sft40.. and i got 410 kcd measured with my lux meter at 5 meters. On a Lishen 9.6amp 5000 mah battery.

Definitely an eye opening experience with the SFT40 in the FT03.. It out-throws my L21a sft40 and my ft03's beam isn't even perfectly tuned like the L21a is.

I wish i could tag JaredM on this post- i sent him an sft40 that he told me had black dots on the phosphor, which was probably from me when i was uninstalling it from my EA01... I wonder if he could save the LED.

I attempted to salvage the emitter but there are little chunks taken out of the phosphor now that cause blue leakage. The cct is probably 10,000K or more now (hard to estimate as its exponential). It’s still installed in the TN31 waiting for a transplant. I never boosted the current up from the 7A I was running the PM1 at. I will swap the SFT40 from my incoming L21b to get the beamshots and readings I promised. I’ll turn the driver up to 9.5A as well. Trying to get my hands on a good camera and tripod. Thinking of picking up a Sony A6000 and a decent lens.

nice, thanks for the info and for responding man. Looking forward to it!