Replacement LED?

Sounds about right. If you can light it up, just measure the battery current drain, and calculate or estimate the power dissipation.

If you can remove what I believe to be a lens, I think you'll find that the actual LED is rather conventional and can be found in the Cree catalog. If you sort the above list by power output, there are only 3ea 1w LED's listed. Just find the right die size and good luck soldering the tiny chip. You can also dig throught the current flashlight offerings and see which 1w chips are popular.

Learn by Destroying.... then buy a new flashlight.

On 22 Mar 2016, DaveC wrote (in article):

Just measured working light of same model: using power supply @1.5v (measured at flashlight battery terminals), the current from the ps is 400 mA. Estimating 75 percent efficiency that makes about 450 mW.

So a 1/2W replacement LED might be what I?m looking for.

Thanks.

I found these:

Looks good, no?

Please deduct one point for spelling my name wrong.

No. I thought you said your flashlight was bright and possibly 1 watt. Those are common 5mm LED's with 0.5 watts maximum. These photos look very much like what I would expect to be hiding under what I believe to be a lens of some sorts: This looks a bit closer:

That data sheet is also slightly insane, specifying the luminous flux as: Lumen typ.: 19 mcd Lumens are measured in umm.... lumens, not millicandelas. It is possible to convert between lumens and mcd's using the viewing angle: Anyway, 19 lumens is not very bright but probably good enough for a pocket flashlight.

And I tried so hard to get the ?Lei/Lie? bit right! (c; 2 steps forward,

One of those images (located here):

looks exactly like the one in my light. It?s squat, with very (relatively) large yellow die(?) in the center. I don?t think there?s a separate lens. Maybe it?s molded to focus the light (integral lens)? Wish I could find that LED other than @ Alibaba...

Ah-HAH! From that Alibaba image page: ?strawhat LED?. Search turns up similar-looking LEDs. Searching on the terms ?strawhat? and ?dimple? tells me that this form-factor is for radial distribution of the light, not throwing a beam. Which means the flashlight designer wanted the reflector to shape the beam, not the LED.

So I?m looking for one of these types.

Thanks.

(Why are my search skills so crap? Google keeps returning Manga images and cartoon faces...)

Hmm, that sounds like a good idea to put in my planned LED torch project, which was going to have a manual dimmer anyway. I guess an LDR would be suitable? Maybe mount it in a small tube to make it directional?

I guess I'll have to find an LDR and wave it around with my multimeter attached. Ahh, the dignity of research. :)

News to me. In what way are multi-layer ceramic caps and soldering irons incompatible ?

Rapid, uneven heating can crack MLCC capacitors. YMMV.

Cheers, James Arthur

Not a bit.

I've seen a couple of the larger MLCCs crack. Now I tap both sides of those with the iron beforehand, to even out the heat. Seems to work.

Cheers, James Arthur

Like ESD, it's the latent damage that's worrisome. I don't hesitate to use an iron but I'm not too worried about what happens next year (or if it even fails this year - just have to fix it).

Oh, there's incompatibility, all right. At soldering temperatures, lots of surface-mount devices are very delicate, a little mechanical stress and they come apart. MLCC capacitors are made of ceramic (OK at temperature) nickel-alloy endcaps (OK at temperature), and tin. When you get to the softening temperature of tin, the endcaps can come off with a little surface tension or jostle from an adjacent solder iron tip.

Really, before I got my pick and place machine, I hand-soldered about 25,000 .1uF 0805 capacitors. NEVER ONCE had a bad one. I still hand-solder a fair number of low production boards and prototypes, and have never seen a problem with MLCCs.

Jon

I've never wrecked a 100nF 0805--those have a pretty small thermal mass. The couple(?) I cracked were fatties, 1210(?) and as tall as wide IIRC.

It hasn't happened in a very long time though, despite me not always bothering to be careful.

My current project uses a number of 1210 22uF 25V MLCCs but I didn't solder them, Mr. Reflow did. :-)

Cheers, James Arthur

I have a set of the Metcal tweezers that work well for that. (You need normal tweezers in your other hand if you want to reuse the part--otherwise you have to shake it off and it gets lost.)

Cheers

Phil Hobbs

I don't like to reuse parts anyway but I've found that if I clean the tip/tweezers with IPA (not the drinking kind), parts don't stick nearly as badly. Burnt flux is sticky.

Tap the tip with the part on the edge of a little tray or dish, and the part (with stray solder blobs) drops in the dish. Better than having stray blobs roaming your desk looking to make trouble, even if you don't re-use the parts.

Clifford Heath.

Sorry for the delay but I missed the followups to my comment.

Thermal shock easily cracks MLCC caps. I learned that the hard way while fixing several Apple Mac Mini computahs, which feature a collection of MLCC on the bottom of the main board. The original failure mode was shorted MLCC caps caused by either thermal shock or board flex. The bad ones were easy to find with an ESR meter. However, when I tried to install replacements (and guessing the part value because Apple doesn't supply service information to non-authorized repair shops), I managed to crack and short several known good MLCC caps with a soldering iron. Having learned the lesson, I used some solder paste and a hot air SMT reflow gun to do the soldering. I also pre-heated the PCB and let the caps cool down slowly. I don't know if that was necessary, but it worked every time. I'm told that two solding irons used as a tweezer also works, but I haven't tried that yet.

You'll find some more details under: Lots of articles and guidelines on handling and soldering these caps, some of which warn about using a soldering iron. For example:

1. Soldering with a Solder Iron Attachment by soldering iron is not recommended. A heat shock may cause a crack in the MLCC chip capacitors, however, if solder iron is used, the following precautions should be taken: ... (etc)

Damage Prevention When Soldering Ceramic Chip Capacitors Hand Soldering - A pencil type soldering of 30 watts maximum and with a diameter of 3 mm maximum should be used. - The soldering iron tip temperature should be less than 300C [572F] and maximum contact time should be 5 seconds. - The soldering iron tip should never come in contact with the component body. Ever try to solder a small MLCC cap without touching the body with the soldering iron tip? Good luck.

In order to prevent damage (cracks) to the component that can be caused by localized rapid heating and heat shock, preheat the chip, for example, to prevent it from being subjected to heat shock.

I've heard these stories a number of times. And, yes, maybe some people use insanely hot irons or in some other way cause this problem. And, some really large caps are prone to this damage. But, as I say, I have hand- soldered over 25,000 0805 MLCC caps of modest value without seeing this problem. I use a very good Weller temperature-controlled iron, and run it at a modest temperature. Much better to use an iron with really good thermal conductivity at a lower temperature than one with poor conductivity at a very high temperature.

Jon