Thank you so much , that sure beat sifting through all that stuff to find the right one. I will scan the thread and look up dis-assembly information tomorrow evening. Maybe do a quad bypass too.
All good! From memory, it’s just two screws to get at the MCU.
It depends on how long the led wires are. If long enough, you can tilt the driver for clip access. If too short, then you have to remove the screw for the reflector, move reflector and unsolder the wires from the mcpcb.
I can’t remember if the newer models use a single screw or double screw. Here are pics of the reflector back side.
Ah yes, good point. I tend to forget that!
This is my newly modded Q8. Xhp50.2’s… I ran this next to my buddies stock q8. His got hot quick… mine stayed relatively cool considering. It’s really bright… will burn ur hand in a few seconds. This is my first time posting picture. I’ll try and get some beam shots later.
oweban
Successfully flashed! 
Thank you again so much . For the disassembly instructions (my wires were long enough that I only had to flip the board to the side) and especially for the link to the hex. I went and looked in there and there are versions going way back, I surely would have stopped at the first Q8 I saw.
All good! TK has done some incredible work with thermal regulation in the latest release.
Gofastdodge, I found the rest of the screws. If you PM me your mailing address I’ll send you some.
It’s nice to know, during these trying times that people can still be generous. It’s not hard to be kind to one another. Let’s all do our part to help our friends and neighbors.
I have Q8 with the stock Sofirn drive I’ve modded to run XHP50.2’s. I did a full tail cap bypass by running 18awg from the springs through to the screw terminals, replaced the 4 screws with copper ones, and used a copper bolt to hold the reflector in. Heat and output from the LEDs seem to be fine.
However the MOSFET on the driver itself is getting alarmingly hot. Even a few seconds at full turbo with VTC5s leaves the driver battery contact ring scorchingly hot. I’ve added some silicone to create a more direct thermal path from the MOSFET to the shell of the light, and this seems to have helped a little.
What I’d like to know is how much heat should be concerning here. Is this something where I’m just pushing the components too far or is the MOSFET ok with the heat? I do have some SIR404DP’s on order and planned to swap one in, but I’m not sure if the XHP50.2’s are just too much for any sort of sustained output at full turbo.
I don't know the amp draw offhand of a XHP50.2, but it's high. The stock FET is not so good, so yes a SIR404DP would be better. Actually any of those FET's from a driver made in China is probably a fake, but most of the fakes actually perform fairly well.
Not sure how much that effects the brass contact ring, however. I'd be sure the brass ring is clean and properly treated. I'd sand it smooth, maybe apply thin amt of conductive protective grease, like NO-OX-ID.
The better FET's, are there are a few, should stay cool, and are rated up to 60-100 amps or so.
I've been using these more recently: BSC009NE2LS5ATMA1, by Infineon, https://www.mouser.com/datasheet/2/196/Infineon-BSC009NE2LS5-DS-v02_00-EN-1731220.pdf. Actually it's been a couple years I've been using these. There may be better ones now?
The FET should be fine. The contact ring is getting HOT from all the current the 4x50.2 3v LED’s are pulling… think about how HOT your springs would get, IF you didn’t bypass them…they would melt down… now each battery has a spring/bypassed and all 4 batteries are going thru one common contact… It is going to get really HOT. I’m running the Infineon FET and 4 VTC5A’s and mine has had zero issues since the very first 50.2 3v came to be…
Yeah, ring I sanded smooth and I’m using something called “MG Chemicals 8481”, which is a carbon-filled, silicone-free, electrically conductive grease. I think it’s largely the same thing. I actually read your discussions on Q8 mods as part of the planning effort for this. I went with the SIR404DP as it was cheaper (and for sale on eBay), is the Infineon part substantially better?
I think mainly this is the first light where I’ve turned it on and immediately become concerned that I was doing something silly.
It’s very much the FET that is creating the excess heat here. You can feel the heat coming from that specific component when it you crack it open. I know fets do tolerate heat to a point, but it was starting to get to the point where I was concerned it would de-solder itself.
My interest in Q8s has been rejuvenated with all this talk of finally a 3V XHP50, but the only problem is I’ve grown quite fond of my Q8 with Luxeon Vs…… I know for a while most of the parts were available, is there anywhere I can get just the head of a Q8 and mod that so I can swap between the two? I’m also sad seeing that Q8s don’t seem to come with Narsil anymore?
Haven't heard of Q8 heads being sold. Of course it wouldn't be much, if any, cheaper than a full Q8. All the $$$ items are in the head.
This Q8 looks like NarsilM, though the Anduril version seems to be cheaper now.
Yesterday I have bypassed the springs of my Q8. The difference is like night and day.
Without the wires attached, the voltage difference between the light`s casing and one of the wire was 0.23V.
After attaching 3 of the 4 wires and using one wire for probing, the voltage difference dropped to 0.11V.
So I guess the LEDs are now getting around 0.15 more volts with almost fully charged VTC6
Did something similar with my Sofirn Q8.
In real life there are four bypasses of course
I used AWG20 end they don’t cross.
Is there any care that must be taken to drive those SST-40’s in the Q8? I’m using 4 Samsung 25R in a stock BLF Q8 and plan to use the LED4Power MCPCB populated with this LED. Any chance they’ll see more than 9A each?
Pulling 36 amps in a Q8? Hhmm. Certainly no chance if not using bypasses, and 25R's, though good, are not the best cells around - 25S's are at or close to the best. The bottleneck could well be the single pair of LED wires for 4 LED's, and the single FET. The ratio of 1 cell per LED makes the Q8 superior to most multi-LED lights, but hitting a peak of over 9 amps per SST-40 LED is challenging.
I'd say with stock springs, stock FET, and stock wires, it should be safe even with the best cells.
Ok, thanks, Tom 