Convoy boost driver problem

Flashlight Modding and DIY Parts
21

So I have the sd3 and I love the host. I did an emitter swap on it and it started acting weird and wouldn't work if the bezel was tightened down too tight (normal flashlight tighten bezel as much as it'll go, this had to be tightened then backed off a whole turn).

I spoke to some members and ended up swapping in simons 8amp 12 option 3 volt driver and thr. Same thing happens. Every other function of the driver worked great and I could program it and everything, but if I tried tightening down the bezel all the way they flashlight wouldn't light up. I just gave up on it unfortunately..

any help? I only ask because this is a thread about a issue with an amutorch sd3 with a Convoy driver ... thanks if anyone has a suggestion about why this woul happen with the stock driver and then a replacement driver. I put the driver in a m21a and it works fine.

22

I guess first I might try to reflow the emitter, make sure it's seated and has enough solder. And then checking for reflector shorts/contact since compression seems to be the common denominator - some magic marker on likely contact points can show if that's happening (reflector, led wire points, etc). Check for stray solder splatter and scuffs/cuts on the mcpcb surface that could expose copper or traces. And something that comments about the FWAA taught me as well...be sure the wire insulation on the led wires is protecting from contact with the mcpcb where they pass through and over its edge. Maybe buying a thicker lens would help, at the expense of a few photons, or double o-rings (above and below the lens if that works)?

23

I was going to wait till tomorrow to post my verdict on this light as I took it out for a lengthy stroll tonight. The issue of the sometimes next mode after a quick OFF and then ON has gone. Also, I had a few stutters on the moonlight after replacing the resistor. These have gone also. What I did do prior was to scratch off the side of the spring pad that I believed went partially under the resistor, but mostly some more cleaning of the flux in some of the crevices. Now that I’m more than happy with the mod, and having troubled the members, I decided to not order other drivers. Sorta not throwing in the towel but mustering on.

@Artiet59: I have not quite understood why this driver behaved erratically, as the replaced resistor once soldered onto the board gives 119.2 kΩ, which tells me the previous value of 121k was good and confirms my Uni-T SMD DMM does in fact measure on board values. I’ve been penchant to my theory of residual flux cleaner creating some electrical mishaps, but your observation of loosening the bezel injects another mystery. As a designer and machinist by trade, the technicals are lacklustre: non-reversible tube, poor choice of thin silicone ‘O’ rings, shallow driver cavity, and, probably in line with your problem, the lack of allowance between the head/tube/tailcap. A 21700 just so barely fits lengthwise. My unit had a standard zinc plated washer on the switch assembly – which did nothing more than limit the travel of the clicky. Next time I dismantle the head, I’ll be checking the flatness of the shelf and runout to the bezel threads. I suspect the CNC operator is not very finicky and some machining issues may be at play. These lights are economically made, and the trade-offs are apparent. All three SDs produce a double outside light ring. And it’s not the reflected glass edge that is the problem (I painted matte black on 2).

There are some strange discrepancies in these lights. I’ll give it a think the night over (sometimes a brainstorm as I eat breakfast).

Edit 06/29/21 14:38

I don’t think a less than flat shelf would cause your problem. As Correllux says, something is binding and cutting the circuit as the LED / MCPCB is compressed. If it were to cause a short, wouldn’t the driver fry?

I opted to push the wires on the head’s wall – too little space to push them in.

I should re-do that solder job and while at it, tap those retaining holes. A couple of screws would butt against any twisting movement. Would need to file the wire passages for a better alignment. Your problem may be related to those out of alignment passages. Would there be a break in one of the conductors? But you had changed the driver and I can presume the leads.

So my other thought, a small solder bead on the perimeter of the package, when pushed with the gasket, could lift an improperly flowed LED. Maybe check around the LED footprint and scratch off any beads.

Sorry for my earlier rambling – early morning hours half asleep.

24

I'm a big fan of Amutorch lights, got a sizable collection of them. Most I've modded, but as I've said many times, not a fan of power switch lights, prefer e-switch.

That resistor in the OP pic appears to definitely be a problem. It's got what appears to be a conductive coating. There may not be a full ground, but partial, so confusing when tested. There's solder on that driver where there shouldn't be - not sure if that was how it came or not, but if it came that way, it's a sign of either an attempted fix or some sloppy handling. Except for those solder deposits, it looks pretty clean.

Artiet59's issue of tightened bezel wouldn't work, sounds like a classic MCPCB solder joint contact to the conductive reflector. I'll use kapton tape for that, but also try to get those solder joints as low as possible. What I've done is tap them down with something like a larger nail set. Solder is quite easy to deform. Kapton tape is cheap enough and a spool will last forever. I got like 3 different sizes (widths). I typically put the kapton tape over the solder joint, but some apply it to the back of the reflector - either method should work, but if it's making contact, there's a chance the reflector isn't sitting down as well as it should be.

Driver replacements have their risk. Something you have to watch for is clearance for the IC's - the driver may fit in width, but sometimes stock drivers are laid out to accommodate the housing. I've had to file or dremel things down sometimes to get clearance. A grounded IC can cause problems, maybe intermittent.

25

Much appreciated info Tom. Yeah, that resistor is partially conductive (maybe in the MegaOhms) and I’m to blame. I did a stupid thing in cleaning the board with a caustic cleaning solution. Alcohol didn’t remove the splattered flux into the existant flux (or perhaps a sealing coating?)

Artiet59’s issue; wouldn’t a short cause the driver to fry? Maybe there’s an overvoltage trip that is quick enough? Not questioning your knowledge, just thinking out loud.

I had to knock out some material to fit some of those drivers. Other times, Kapton is my friend.

Edit: I figured it out. The negative would go thru the reflector then thru the body. The MCU (or other as boost driver or OP amp) detects a spike and shuts down.