I do not have that specific flashlight but have experienced intermittent and
DOA with other small imported flashlights.
In all of my cases it was related to the way the PCB that the LED mounts to
returns current to the battery. The PCB is a circular affair which has a pad
in the center of it that presses against the center battery\battery holder
post. This provides one side of the circuit. The outer diameter of the
circular PCB also has pads on one side of it. Think single sided PCB, not
two sided or with plating on the edges of the PCB, but only on one normal
flat side of the PCB. These pads on the flat part are suppose to contact a
"ledge" in the the metal body of the flashlight. This ledge provides the
return circuit and also prevents the PCB from falling into the body of the
flashlight.
The current flow is "battery -> pad in the center of the PCB -> LED and
related current regulating circuits -> pads on the flat outer diameter of
the PCB -> ledge on flashlight body -> flashlight body -> switch in the cap
on the end of the flashlight body -> spring in the switch\cap -> other end
of the battery.
In all cases my failures were related to the PCB being a very poor press fit
into the flashlight body and the outer diameter pads not contacting the
ledge. If I would press on the lens to push the PCB into the body they would
light up. Note that "press ..." did not actually cause the lens to move any
discernable amount. All is seemed to do was press the outer diameter
contacts down hard enough to actually press against the ledge and work.
The pressing incantation seemed to permanently fix some of them but for
others it was 'only worked while pressed'. Needless to say those that would
only work if I had my finger on the top of the lens were classified as "did
not seem to fit the spirit of useful flashlight design" and were trashed.
Yours may have much better construction techniques.
Arvid
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