Luminus SST-40, a N4 BA bin tested

So I tried a N5 BC (Voltage: VH) in my M21A. My LD-A4 driver in the light was ordered with 8-12 Amp range so I set it to the bare minimum. Tail current was measured at 7.94A and voltage across the LED at 3.446V. It’s obviously bright AF, quite close to the sliced dome 3V XHP50.2 that it replaced.

The XHP50.2 measured 3.226V across the LED and the MOSFET probably took a hammering and caused the driver to overheat the whole time.

I will have to replace the LD-A4 with a LD-B4 driver and the corresponding PCB to combat the hot MOSFET. But I need some advice…….
Will it be OK to run the SST-40 at 8A? Or should I dial it down to 7A? The light is being used as a tactical light with high to low modes, no mode memory. So it always starts in turbo.

8A is about perfect.

I’d also put a copper shim on the MOSFET to help it with overheating.

Where can I buy a copper spacer? I have silicone cubes and sheets that I can use to space it. Otherwise I’ll have to make my own… The MOSFET is definitely running cooler with higher Vf of SST-40, but more cooling will definitely help. It’s a pity my 7-9 Amp LD-B4 failed for some unknown reason.

Oh, you just take a copper sheet, and cut a rectangle the size of the MOSFET over it.

Wow… Do I just tape it to the MOSFET?? Sounds risky. I thought about using 1mm silicone sheets on the driver side of a thick circular copper disk and insert silicone cubes on the shelf side to add some pressure as the driver is pressed down by the retaining ring.

Well, don’t you have some thermal adhesive on hand?

That’s how to do it.

Otherwise, you can risk a short.

Yeah I have some… I will then fill the cavity between the shelf and driver with silicone cubes to add pressure and that little bit extra heat conductivity.

Thanks for the advice.

if you really mod on it switch to a better MOSFET, those mosfets are designed to get heat lost to the PCB side, adding copper on the top wont help

with SIR404 or Infineon with 1.2-2.5mOhm there is at 8A no considerable heat present, those can go up easily to 25-30A
2mOhm*8*8A—>0.128W heat

look into the Emisar D18 for example where the FET is quite stressed
1.25mOhm*35*35A—>1.53W

with a considerably good PCB design preferrred 2OZ copper and thermal viases 1-2W heat are OK

Mosfet resistance is irrelevant in case when linear driver operates in linear mode, in that case power dissipation in mosfet is (V_batt - V_led)*I_led.

So switching to other mosfet won't change a thing. Improving thermal path between mosfet top side and pill does help a lot, but it's not easy to make very good thermal path for deep pills/driver cavities. Example how to do it is S2+ thermal kit:

https://led4power.com/product/ld-a4-thermal-enhancement-kit-convoy-s2/

But again, this is not simple for many flashlights and cost is high, if LD-B4 can be used, it's the best method.

Your calculations are valid only when mosfet is in saturation mode - direct drive, where I^2*R loss it the only cause of heat generation.

Interesting results. I always thought dedoming this shifts the DUV higher which is the opposite of what you got. I wonder why the dedomed SST-40 NW in the Nightwatch NI40 is so horribly green +0.02x.

I might slice my FT03 SST-40 NW since there are now replacement LEDs available. I’ve never attempted a complete de-dome though and dont really want to get into doing that myself.

Have any one successfully dedomed SST40, Not slicing, i want to dedome it because i got a very cool white sst40 and i want it to shift color plus the throw

I just got 10 more SST-40 from KaiDomain. Do you want me to try one for you? What methods of de-dome do you have at your disposal? I would want to do what you could replicate, or it wouldn’t be much use to you. :innocent:

EDIT: Actually, just realized, I have some dead ones I burnt up. I’ll try those first! :smiley:

AFAIK Maxtoch seems to be the only one reliably chemically dedoming these. Seems it wasn’t easy when others tried?

Do you have any idea what chemical they might have used?

Nope dedoming these is tricky i think heat might work best. I killed 2 in petrol trying to dedome them. One worked with heat then got killed by a reflector sliding.
I just had one dedome its self now lol the silicone burnt up months after a sliced it. I don’t think its the LED fault it was out of the light for ages i just put the sliced SST40 back in my FT03 last night. Could of had dirt on it from storage as i had no issues with it till now and i used it sliced for over a few weeks. I had a XHP50.2 in my FT03 for the past few months.
Luckily i noticed the smoke and turned the light of i cleaned the dome with some alcohol and it seems to work still.

So I got my 5000K SST-40 LED’s recently… DD bin from Kaidomain and DA bin from Convoy. At low current the DD is a lot greener than the DA from Convoy. At medium current the DD is yellow and DA more white. At high currents the DD is white, where the DA almost has this slight magenta tint to it… I then went ahead and put a DA in my S2R Baton II with a beaded optic. And I can live with it, seriously. I will actually use this light now. And I have recently used my FW3A 219B SW40…. Obviously the color rendering is not good. But it’s an acceptable tint compared to any other SST-40 or XM-L2 in any of my Olights. I’m gonna order some more!

edsg - How did you kill them in petrol trying to de-dome them?

No idea. I think people only came to that conclusion cause of the macro photos of the LED make it clear it wasn’t sliced and diced like some of the Kaidomain ones or otherwise.

The Silicone stays on and takes the bonding wires with it. No matter how long you leave it.

I have 3 more that i sliced the performance difference isn’t to much between the two.