Foursevens QPA head on Fenix LD20 and nitecore MT21A/MT21 body issue

I was able to pick up a quark pro QPA head for $17 on fourseven's clearance section of the site...said it would be an xpg, but turned out to be an xpg2! (nice)

Tried using it on nitecore MT21/MT21A and fenix LD20 bodies; the head would screw on all of the different bodies and would work just as it should, but occasionally there would be an issue when trying to use it. The highest output/strobe sometimes won't turn on and most commonly the lower modes won't cycle through as the led would barely light up (fraction of a moonlight mode). This is totally random when it happens and the only way to correct it is by taking the head off and putting back on...then the light starts working normally for awhile. If I try pressing the tail buttons I get nothing.

I've seen people mention legoing 47s heads, etc, but never seen anyone mention issues such as this.

Any thoughts would be welcome!

:thumbsup:

I Lego all the time, but only within 47s OEM parts. Does the light function correctly on an OEM tube/clicky (do you have them)? The threads might "fit" on another manufacturer's tube but not be quite right and cause connection problems. Careful, aluminum is very soft, and you can easily gall threads this ways.

Anyways, the Quark heads get their loose bezel negative circuit path through the threads so the tube threads must be unanodized. The tight bezel circuit path is through both the threads and the outer ring on the PCB, so the threads must also be long enough for the bare battery tube edge to reach it reliably.

Try THIS paperclip bypass test to the function of the head. You might need to round an end to touch both threads and outer PCB ring simultaneously for tight bezel modes. You can also use a AAA for more room, but don't expect high or max to be very bright.