Question about an Fet driver. New guy here

Flashlight Modding and DIY Parts
1

Hey guys……I’m slowly getting into the understanding of the Fet drivers and how they work.

I have had a few custom lights and currently EDC an okluma TinyDC. I have an understanding of how these triple lights work and have a few questions about a custom I picked up.

I purchased a custom built buy a forum member over on BF And can’t figure out what’s up with it.

It’s a Convoy s2 host with an FET+1 in it. Runs on an 18650. Currently has 7 modes.

I had a few sinner triedc lights with the same platform. So I understand how the light works. Should always start on ML and then soft presses to go through the modes.

This one however is in some type of weird ramping loop.

The light comes on in what ever mode it was left in and then 3-4 seconds is steps down to the next level, and then to the next level another 3-4 seconds after that……and continues until the light goes off.

I tried the 8 quick press to access the programming mode but no luck.

If I quick press about 20 times it will go into a quick two flash sequence. It will two flash twice and then shuts off and reverts back to everything I have stated above.

Any ideas what’s going on?

2

Battery charged?

3

Sounds like Low-voltage protection is kicking in. If your battery is charged up, you may have a bad resistor or short on the driver

4

Yes. I swapped it with another charged 18650.

If I turn the light on and rapid click about 20 times, it goes into that two blink sequence. Does that twice, then shuts off.

It then ultimately reverts back to the stepping down in all modes until it’s off.

So if I turn it on and quick press to turbo, it will step down through all the modes and then shut off.

5

Ok. Baby steps here. I have some questions.

I have soldering capabilities/abilities, and am a very hands on person. (Automotive/welding/fab instructor).

So I’m not afraid to tear into this. I just need some guidance.

Would this be in the head, or the tail switch?

I’m going to assume in the head?

Would this warrant a new Fet 17mm driver?

6

In the head. just remove the brass retaining ring from the battery side and the driver should come out with wires going up to the LED. Just look it over for any stray strings of solder that may be out of place, or post a good picture here if you can get one.

edit: sorry, forgot it’s an S2. You will need to unscrew the brass pill out of the head first to get a better look

7

Here’s the light.

8

Having some issues with pictures.

I tried to use photobucket, but they didn’t show up.

9

I can see the picture. The one on the left labelled “MTN-17DDM” Is the driver. Use some pliers to remove the retaining ring to get a look at the driver. I can’t remember if it’s standard or reverse-threaded though, so be careful on that.

10

Here we go

11

so that whole brass/copper stack is the pill. We want to see the other side of the purple pcb that has the spring mounted to it

12

How does that come apart? I lightly pulled on it, but it’s tensioned by the length of the positive wire(I’m assuming)

Do I need to desolder it from the spring?

13

The inner ring around that purple board is a retaining ring. Those two divots/holes in the brass are points to use a snapring pliers or needle-nose to unscrew the retaining ring. That’s the one that I think might be reverse-threaded.

14

Ok. I’m going to have to hold the brass threads with a pair of pliers to get that loose.

Give me a few minutes.

15

There’s not enough slack in the wiring for me to get it open any more than this.

16

Really? That’s both annoying and very impressive on the part of whoever built it.

Well you can see where the wires come out on top. Are you comfortable desoldering them and eventually putting them back? Putting them back with such short wires will be the tough part

17

Yes. Almost no slack in the wires.

I’m comfortable with soldering

Should in de-solder from the triple optic up top?

18

Well, I put everything back together to set aside for later, so my boys wouldn’t mess with the pieces , and………it started working as should.

I think you were right, there must have been a wire or some solder touching a resistor or another component that it shouldn’t have been.

This has prompted me to placed an order through MTn electronics and attempt to build my own!