Damn it! Been using it day in day out for the last 3 years. It has clocked about 3500-5000 hours of use. Nowhere near 50,000 but something is broken in the head and it won’t turn back on. No proof of purchase so I’m not sure 4sevens will warranty it. Anyways, I contacted them and hope they offer to exhange/repair it.
In case this can’t be done, I’m strongly leaning towards those thrunite baddies.
how did it die?
Just die?
Or did you whack somebody with it. and then both died.
My tail clicky has always been somewhat finicky on my Quark 2x turbo but I don't care since I normally use a 16340 PD-20 Fenix body. It makes a cute little nightstand light that firmly parks itself face down and resists the domino effect you get with skyscraper tall AA 2x lights ..... super low moonlight mode ,super small,super bright ,nice light
I dunno for sure but my 2 year old kid has a habit of using it (turning on/off) and screwing in off/together. I has the occasional small drops but nothing that should damage anything. It was working fine and then 30 minutes later when I needed to use it for toddler as night lamp it failed to light up. Tried batteries, changing my tail cap but would not work. Its the head I guess.
Fourseven’s will take care of you, no proof of purchase needed!
Ten year warranty. They will repair or replace.
Absolutely spot on man. I am totally impressed by the 5 star service support. Extremely fast in answering emails.
Foursevens took care of the problem and have shipped back the flashlight as at 20.02.15. I emailed them asking them what was the problem and they told me the head was defective and that they exchanged it. Hopefully, its a new XML-2 emitter 
What I don’t get is what could be a ‘defective head’?
A burnt out /broken driver can surely be replaced if I am correct.
Is it the led that died from hours of use?
Final update: My Quark X came back today with a new head. It appears to be a XML-L2 head 
Happy to get the newer gen led head! First class service!
Edit: Just tested. Gorgeous floody light. Appears brighter than what I remember. Somewhat greenish tint on low modes (spot) noticeable on white wall. Not of a concern for me
Glad they sorted you out sounds like a good company, I have yet to pickup a quark mainly down to there prices to be honest. But nice to see a company back there products. If they have a sail i may pick one up.
You could try the neutron v2. Its less expensive at $55 shipped. Equally great light and nearly as floody with the added bonus of being able to be used in 1xAA at 480 lumens max and 2xAA at about 800 lumens….
Driver might be swappable, even repairable, but not necessarily for the manufacturer. Sometimes if possible its best just to replace the assembly, or even the entire unit.
I would like to see the neutron v2 with tubes for RCR123 and 18650 making it a universal light and a forward clicky tube would make it perfect. I really like my forward clicky and use it alot at work and home, quick light with no telltale click as a warning.
But as i was there i ordered a ThruNite Archer 2A V2 NW to see what that is like, Low of 15lumens for 96 hours and a Medium of 69lumens for 11 hours, if i like it i’ll get half dozen more to start as SHTF lights and gifts. My LD25 Q3 NW are old but still my goto 2 x AA light i have 2 still in there boxes only taken out to test 3 more in BOB’s.
One word of caution a friend bought a New old stock LD25 and it was a fake knockoff at $60.
ThruNite Archer 2A V2 NW was $33.90 USD / £23.52 GBP with shipping to the uk