On Mon, 21 Mar 2016 10:30:03 -0700, DaveC wrote:
The LED in my flashlight is blinking (2/sec). It’s not the support
circuitry (constant current): the voltage across the LED is constant 4v. I
presume it’s a failure mode of the LED. It happens immediately upon
power-on.
I beg to differ with your diagnosis. Unless the LED has magically
turned into a thermostat controlled flasher, it's not going to do
that. More likely, the LED driver circuit is doing the flashing.
Based on zero detail about the actual flashlight, my wild guess(tm)
would be the big electrolytic that usually goes across the battery.
Broken or badly soldered connections on the driver PCB are also
likely.
http://imgur.com/a/rIRDG
The form-factor is close to a 5x5mm (h x diam). Standard through-hole leads.
But it’s a pretty high-intensity one. Don’t know what makes it so, but I
classify anything with a yellow square visible in the center as
“high-intensity”. Maybe not technically accurate, but there you are.
If it's not too much trouble, could you disclose the maker and model
number of your flashlight? Extra credit for providing a link to the
manufactures web site or China source link. If there are no numbers
or sources, perhaps a photo of the assembled flashlight?
What I’ve found so far is either a standard 5mm LED but not very bright, or
SMD types requiring heat sinks.
Yep. You're looking at the wrong stuff. Maybe something by Cree:
http://www.cree.com/LED-Components-and-Modules/Products
Nope. Ok, I give up. What the photo looks like is a common dome
shaped LED (as in the Cree URL above) with a lens over it. I did some
Googling looking for the lens and couldn't find it.
It’s a great little light, and I’ve not found anything as small,
long-lasting, with single AA that I like as much. And this is a learning
experience, so there’s that.
I have one that meets your requirements. L3 Illumination L10:
http://www.candlepowerforums.com/
vb/showthread.php?376058-L3-Illumination-L10-%28XP-G2-R5-or-Nichia-219-1xAA%29-Review-RUNTIMES-BEAMS-VIDEO
Single cell, very bright, tolerably priced, small, adjustable
brightness, etc. However, there's a catch. It has 4 brightness
levels set by twisting the two sections of the body. No problem
except that it makes it a two handed operation. I would have
preferred a push button at the back end. I've also measured the
brightness (using my highly creative and non-standard procedure) at
about 90-110 lumens (varies with temperature).
Any pointers to a suitable replacement LED would be appreciated.
Again, I don't think it's the LED. The driver board is a more likely
culprit. Put it under a magnifier and see if you can find the broken
trace. Put a light behind the PCB to make it easier to see the break.
If desperate, trace out the schematic and try to identify the LED
controller chip. If it uses an MLCC capacitor, use a hot air gun to
reflow, not a soldering iron tip.
You might also get some help in CandlePowerForums:
http://www.candlepowerforums.com
Good luck.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558