The magic in that statement CK is “Zener mod”. You’re giving more voltage than the high Vf of the de-domed emitters.
You checked the amperage AT the emitter? Never seen one run that high to my recollection, in any light. So you’re pulling 15A at the tail? What switch are you using?
So 2 out of 2 XPG-2’s dropped current when de-domed,but with extreme currents :bigsmile: The XM-L2 didn’t budge.
Something strange is going on,I’ll have to check out the Sinner Cypreus EDC thread-cool light BTW-time for some bedtime
reading(gone 10PM here)and food and 
“So I pulled it and put a domed XPG2 S2 2B and the numbers went where they should be, 4.37A for 955 lumens at start. Then I sliced the dome off. Not the gasoline de-dome but simply cut the dome off with the bond wires still embedded in silicone. I’ll be danged if the numbers didn’t drop right back down to 2.91A and 527 lumens!”
D: dang this is sad news. Can anyone explain Why? maybe you broke a gold thread when dedoming? It makes no sense that the amps would lower so much just because of a missing jelly dome on top. Might as well NOT dedome and take that 1000 lumens instead?
I really dislike the greenish tint from the DEDOMED xpg2 S2 from IntOutdoor. Are there better tints for dedoming?
Because the second time I didn’t take the dome completely off. I used a surgical scalpel to slice it off, greased with silicone grease to help it slide through. Got a nice tight hot spot, didn’t decrease the tint, but lost too close to half it’s output.
I looked back at my Trifecta build from the first of this year. I de-domed the XP-G2 in that C8 and it pulled 4.27A through the Qlite with 4 chips added (12 total). I don’t get it.
With all the emitters I’ve de-domed there’s been a hit to the lumens output. And the tint. Even the MT-G2 with the dome sliced off. But for a select few lights the gain in throw has been worth it. But only in those few cases have I been happy with a de-dome, the majority of the time I wish I hadn’t done it.
If you had a CC/CV PSU it would be interesting to see how high the vF had actually gotten on some of those. A big buck driver sounds like a good match for the high vF problem. Watts still go up, which is undesirable but oh well.
One difference I didn’t point out is that the recent experience was using an 18350 cell size. The C8 earlier this year uses an 18650. The smaller 18350 might not be able to supply the higher Vf at high current like the bigger cell does.
I think the dome acts as a wavian collar to reflect “unseen light” back into the emitter to give that light another chance to become useable light I MAY BE VERY WRONG HERE. So, lumens will decrease because of a dedome.
What I am interested is the Amps that change because of a dedome. Still dont know why amps decrease just because the dome is off. Your case makes it even more extreme because you are still leaving some of the dome and yet you lose 1.46A just because of that! D;
Remember, we’re discussing DD lights here, which are very dependent on Forward Voltage. What DBCstm is saying is that the Vf became higher. Forward Voltage is can be a fickle thing with LEDs.
In boost setups or buck setups with enough input voltage (usually means more Li-Ions than LEDs) Vf isn’t really a big deal. In a DD setup you depend on a great match between the battery’s voltage, the batteries voltage sag under load, and the Vf of the LED.
EDIT: edit for accuracy
Have you ever tried to fill a soap dispenser from a gallon jug of liquid soap? The liquid soap pours in easily (current) to fill the empty dispenser (LED) but if a bubble forms (Vf) it can block the opening and you’ll have a mess on your hands! It’s kind of like that I think, the Vf being higher keeps the cell from being able to match the need of the LED, so the balance the two of em find is considerably lower than otherwise. Like when you KNOW that bubble will make a mess so you pour much slower, keeping a thinner trickle so you don’t touch the sides of the neck on the dispenser and cause the bubble.
Hope that made some kind of sense. Might just be telling on my Mr. Mom status and taking care of my 6 yr old. lol
Quick get a bucket, your electrons are escaping
Oh snap…high Vf 
I like your analogy 
Where do I buy switches like this?
Are these momentary switches?
Yes they are small tactile switches under a push button and retaining ring
OSH Park ~ <-link to switch plate
mammothelectronics.com
standard size tactile switchs will work on that board
Wight, how does the Vf go up…I mean, if the emitter is making 900+ lumens and you use a scalpel to slice the dome off, how does that change the Vf? I wouldn’t think the emitter would be affected, not all of the dome was removed and the bond wires are still embedded in silicone. Blew me away when it dropped back down, I’d done considerable work to gain the advantage I had and didn’t have a clue that the Vf would still be affected this way.
All in all, believe it or not, I’m about to pull the Luminus SBT-70 and go back with a de-domed XP-G2. I liked it’s color, beam profile and lower amperage draw on the small 18350 cell. Best all around output for this smaller light. Am I a glutton for punishment or what? 
And to make matters worse, I cannot find the filed down 16mm Noctigon that I’d used to bring the de-domed emitter up into the reflector! It’s AWOL, I’ve looked all through my entire kit. Will have to file down another one and all of this change has to be re-flowed as it’s all soldered together on the copper pill, which means the entire light engine has to be disassembled, re-flowed off, re-flowed back on, then reassembled. AGAIN! (This will make the 5th time if I go through with it) [actually the 6th, as I’d re-flowed the star to the pill and assembled it originally, only to find that the star needed to be raised to focus the emitter]
Edit: For the record, with an BLF17DD driver on an SST-50 which is mounted on the original aluminum star, it goes thermal at a bit over 9A and turns blue, dims down and is prepared to stick it’s head between it’s legs and kiss it’s A goodbye. It’s rated for 5A.
I do not know! I could tell you a lot of (uneducated) guesses, but I really have no understanding of what determines initial Vf, what affects it after that, etc. I think I’m a long way away from understanding all of that. That said….
First of all, let’s not rule out that something just went wrong with both dedomes. You reflowed these emitters with lots of heat (reflowing MCPCB onto heatsink) and did both dedomes before reflowing the MCPCB onto the heatsink. (I think?) Did you test the Vf before and after the reflows?
EDIT: see DBCstm’s reply where he corrects me on the strike-thru text.
I re-flow first, then on the initial build I gas de-domed it. The second time around I had the XP-G2 S2 2B in the light, ran amperage and lumens tests, then sliced the dome off while it was still on the pill. No more heat. Initially I didn’t slice it deep and it was keeping around 4A, I sliced it further and it went right back to where the first XP-G2 R5 1A started out with the gas de-dome. Made no sense. Still makes no sense.
That said, after taking the first one out (which means re-flowing and pulling the emitter off the star, the star out of the pill) this morning I re-flowed that original XP-G2 R5 1A onto a new star and put it back into the Cypreus. Same 2.85A I was getting in the first place. Tight beam, nice tint, good throw, and it’s gonna stay like this forevermore.
Yeah, so much for guesswork. As I said, I have no understanding of this behavior, but “Forward Voltage is can be a fickle thing with LEDs.”
I’ve pulled dies off of the substrate, that would be my next far-fetched idea - a partially disconnected die. On at least one of the LEDs I destroyed that way the dome was on. (I was reflowing at a way-too-high temperature) When I press down on the dome it works.
I really don’t think that’s likely to be the correct answer. I’d love to hear from one of the gurus on this subject.
Very difficult to pump amps through a de-domed XP-G2.
I thought I’d done more though when using one in an HD2010. But that was back when everything was stacked 7135’s. I wonder if that makes a difference? Would the regulated driver fare better in this situation than the FET driver? Maybe I could try a Qlite with like 2 or 4 added chips, see what pushed through.
It should make no difference UNLESS you increased the input voltage to the 7135-based driver. You might find worse performance with the 7135 based driver on the same voltage as the FET driver, but I’m not sure.
With either driver the battle is battery-voltage-sag vs high-Vf. Since the 7135’s are linear regulators you can get away with batteries that would normally poof the emitter or create an unreasonable amp draw (the extra volts will show up as heat at the 7135’s). I’d say 4s2p Eneloop AA should give you plenty of juice. The Vf can’t be that high. If it is, add another 1s 
A CC/CV bench PSU would be great for collecting data on this, but I don’t have one. I do have a pair of XP-G2s and I just dedomed one. I suppose I could hook them up to my cheap Chinese 3A CC/CV buck converter thing and see if there is a difference in Vf, that would be interesting.
Do you think that a dedomed Xgp2 S2 is green? I have two and they are so green ):
The only S2 I have used wasn’t gas de-domed, it was sliced. And no, not green. Matter of fact, I haven’t really had the tint issues with the XP-G series when de-doming that I see with the larger die.