Touchscreen nichia D4 - YouTube There’s a link on my YouTube channel. I don’t know why it always uploads 240p but you can see what I’m talking about.
Try this, take the tail cap off and lay your finger across the battery and the bottom of the tube.
Does it still light up?
Moderator007, no dice. Just tried that. Doesn’t glow at all. It has to be in the driver cause it doesn’t do it when the tail cap is unscrewed slightly. So it’s like how an e-switch needs a small amount of current to work. Maybe it’s leaking by the e switch. I really have no clue. Interesting though right?
No idea what the problem is, but I’d love to see some video of this.
I put a link a few posts up. I put a video on my YouTube channel. If you watch you can see how the pressure of my hand (surface area of my hand on the light) affects the light output. Still it’s all less than a lumen I would say almost certainly.
And I have to say, normally something like this would bug me like a speck of dust in my reflector—which btw using your tongue really is the best method for cleaning one—it’s actually kind of cool as long as it’s safe. I guess time will tell if it’s safe.
I kind of think there is something touch in the tail cap. And it maybe very small with no more light than its making.
When you stuck your finger on the battery and the tube should be the same as you holding the cap and touch the head.
I just pulled my D4 out to look this over, the tail is always connected.
I’m trying to figure this one out but that’s just strange it acts that way.
Maybe you are just are a good conductor. Too much salt 
.
I have seen this issue before
The only explanation I can give is that the LED- on MCPCB has a grounding or low resiastance(conductive acid flux) to the head part, easily to check with DMM
But the D4S has insulated driver and Tube usually, so there cant be a current flow bypassing the driver
seen on Lights like Convoy L6 going instantly to Turbo when you turn on on Tail switch
so you act as cinductor between head and Tube bypassing the driver
Yeah but think about it. When the batter is in and the cap tightened, the flashlight is energized ready to go. When it’s slightly unscrewed it isn’t, even if the threads were bare aluminum, the negative part of the battery is touching the spring and pcb it’s connected to, nothing else. So it needs to be energized, i.e. have potential, for this to work. I mean I don’t think there’s really anything in the tail spring to go wrong or act anomalously. I don’t know but it’s really freaky doing the two person thing and lighting it up upon touching someone else’s hand.
just watched the video. You should sell that broken D4 to me…
read my post and think about it
even with unscrewed tail cap you touching the bare battery bottom it will light up
Sorry lexel I was respondeing to moderator007. That makes sense and without the knowledge of specifics is kind of what I was thinking. I bet you my ground (black) wire is touching the MCPCB. cause for alarm or is it fine?
if its a dead short with worn anodisation on threrad it leads to DD turbo light if tail cap gets twisted on
if its just some conductive residue light will constantly light up at a low level
It looks like you have had this light for awhile. Did you recently mod anything or take it apart?
Looks fairly normal to me the part of the bezel you are touching has no anodizing left on it? So you have current leaking into the MCPCB from some where.
I swear this just came up elsewhere. The FET has no bottom limit on the voltage it senses. It acts like a gate, and the human body voltage is opening the FET allowing a high enough voltage to leak off the battery and glow the emitters.
wrong the FETs gate is grounded with 100k and the MCU pin at ground too so there is no way you can activate the FET in any way
I didn’t think the head threads of the D4 were anodized, but I just looked and they are on mine. I tried to duplicate this with a led some wire and and a 18650. I couldn’t get any light no matter the combination I held them in other then just wiring it up.
I would guess there is some power bleeding through the driver/head contact. But that is just a guess.
the conductive connection does not need to be on the MCPCB can be on driver as well
I thimnk there are different versions of D4 lights very old had blank machined MCPCB shelf while others were anodized