My L-mini is dead - please help me resurrect it

[Fallingwater]

My SSC-modded L-Mini no longer works

It was working just fine the day before, and I didn't drop it or bump it or anything, it just sat on the desk for 24 hours or so. When I turned it on the next time, the LED was very dim. It still goes through its modes, but the light output is next to nonexistant - you only get to see anything if you look straight at the emitter.

At first I assumed the 18650 cell I was using in it (an old, tired one taken from a dead laptop battery) had finally gotten tired of life, but the problem persisted when I powered the light off my bench power supply.

Then I thought the emitter had died, possibly due to improper heat sinking; but when I disconnected it from the driver and powered it with the aforementioned bench power supply, it cheerfully blasted me with light.

The switch has nothing to do with this, as the light malfunctions even when I apply power straight to the driver pill.

The only remaining suspect is the driver itself.

Any idea what can cause this, and how I can fix it?

Thanks.

 

[StefanFS]

It sounds like you have a dead driver. I don't have an L-mini but I think it uses one of the standard production drivers available from a lot of places, eg. DX and KaiD. Easily fixed at low expense.

 

[Fallingwater]

I really liked the stock driver, as it has mode-switching that is IMO better than the various DX drivers, and more efficiency IIRC.

Is there any way to diagnose it and repair it? When I get home I'll take the light apart and take pictures.

 

[StefanFS]

Pictures would help, especially of the driver.

 

[LukeA]

From Shiningbeam: 5 Modes: high > mid > low > strobe > S.O.S
*1100 mA on high mode
*The memory feature will memorize the last mode
*warning: Some 18650/17670 might not work with this model.
*Don't use 2 RCR123A 3.6V Li-ions.

sounds like:
-Can be powered by a single 3.7V lithium battery
-Mode cycle: Hi 100% > Mid 35% > Lo 20% > Strobe > SOS

link

 

[nanotech17]

there is a better one but back ordered - SKU 15880
very similiar to the L-Mini stock driver.

 

[StefanFS]

From Shiningbeam: 5 Modes: high > mid > low > strobe > S.O.S
*1100 mA on high mode
*The memory feature will memorize the last mode
*warning: Some 18650/17670 might not work with this model.
*Don't use 2 RCR123A 3.6V Li-ions.

sounds like:
-Can be powered by a single 3.7V lithium battery
-Mode cycle: Hi 100% > Mid 35% > Lo 20% > Strobe > SOS

link

It's the 'same' driver. There are variations of it that are better, one with only low-high programming and one with several groups where one is low-med-high. They are very robust and really hard to kill. I wonder what happened with this one?

 

[yellow]

I recently purchased a Model 1 (1*18650) and a Model 3 (2*CR123), because of the cheers in here,
and am very disappointed.
especially the crappy machining and that the body is a bit to short to usefully cover the whole cell
(that seems tp be a problem of many makers, why is it not possible to make the body 1-2 mm longer????)
Imho in almost no way tremendously better made than the cheaper DX-offerings - at least mechanically wise

Get a Jetbeam Jet III Pro ST, thats what I got now and it is much better, in every aspect (but also 1/3 more expensive, of course) - worth the money

 

[Fallingwater]

Stefan: I wonder that myself. Had I dropped it, or drowned it, or done anything to damage it, I'd resign myself to fate. What bugs me is that I did none of that - one day it was working perfectly, and the next it was broken, for no apparent reason.

Here are the pictures.

Back of the driver, with terminal in the middle:

Once removed from the pill, there's a metric ton of thermal goop on the driver.

I remember asking Shiningbeam/Lightbug about it when I first opened it, and he said he had no idea why it was there, but it wasn't a problem. So I left it there when I put the light back together.

Removing it for the following picture took a surprising amount of meticulous work.

Nothing seems knocked out of its place, and there was nothing rattling inside the pill.

especially the crappy machining and that the body is a bit to short to usefully cover the whole cell

You may have gotten a dud. Mine has very good machining and no length problems.

 

[LukeA]

My money's on a broken inductor.

 

[nanotech17]

My money's on a broken inductor.

+1

 

[Fallingwater]

So how does one test an inductor? Where do I get another one (I presume it can't be fixed)?

And how does an inductor break with no mechanical shock?

 

[LukeA]

So how does one test an inductor? Where do I get another one (I presume it can't be fixed)?

And how does an inductor break with no mechanical shock?

You could ask Shiningbeam where the boards come from. I wouldn't try to change inductors. I don't think the new one would survive it.

What I would do is put in a multimode AMC7135 board. No inductor--much more mechanically durable. They also have fewer parts, which is another plus plus for durability.

I don't quite know why the board even needs an inductor. The AMC boards and the D2DIM get by without one.

 

[Fallingwater]

Why wouldn't the inductor survive? They're that delicate?

How's the efficiency on the AMC7135 boards?

Is there one with two or three modes that drives the LED at its full rated power? Ideally I want Low-High or Low-Med-High, no strobe or SOS.

 

[LukeA]

Why wouldn't the inductor survive? They're that delicate?

How's the efficiency on the AMC7135 boards?

Is there one with two or three modes that drives the LED at its full rated power? Ideally I want Low-High or Low-Med-High, no strobe or SOS.

KD has a 2-mode AMC7135 board (1050mA and 150mA) with memory. So if you keep it on low until it blinks once it will start in low or if you flash high for less than about three seconds then turn it off it will start up in low.

The AMC7135 datasheet doesn't talk about efficiency, but I'd imagine it's decent. The chips aren't doing very much to the current, if that makes sense.

I have one of those 2-mode boards in my TR-801 and I really like it.

Here's the link (single, 5pk.)

I just read the part of your L-mini review where you talk about the mode switching. The 2-mode board does it the not-so-good way--and I wish it worked like that L-mini board seems to have. To change modes after 2 seconds you have to do a double-tap.

But I think that that's still better than having to cycle through strobe and SOS.

 

[Fallingwater]

When the L-Mini died I repeatedly tried to get the driver to work, but it just didn't. The LED only ever showed a faint glimmer. I tried another time after that maybe two months later, and it still didn't work.

Today, after receiving some new regulated drivers, I went to work on the L-Mini. Before definitely tossing it in the garbage I tried the old driver again, and now it works! The LED is again shining at full power.

I cannot explain this. Why would a driver spontaneously stop working, stay dead for several months, and then resurrect all by itself?

It ain't going back in the L-Mini though, since it's obviously unreliable.

 

[nanotech17]

that is very weird but which driver do you use now?

 

[Fallingwater]

I want to use this, but it has stupid group-modes and no low voltage protection. I'm waiting for the parts to modify it with a custom interface and low-voltage protection.
While I wait I'm using one of these two-mode, 3xAMC, low-voltage-protected buck drivers (I had to resize it a little bit with a bench grinder).

I must say I'd be tempted to go back to the original driver and hope for the best, if it wasn't that it has strobe and SOS, which I hate with a passion. The 3AMC doesn't, so I'm gonna use that for the moment.