Burnt driver..

Flashlight Modding and DIY Parts
1

Hi. Hopefully I'm posting in the right category by posting here. I don't really see any troubleshoot/servicing category or something alike, so this seemed the closest.

So, my Manker U23 just died of death the other day, setting the record of not working for 48 hours since I've got it, Yay!.. What happened was I was playing with swapping emitters, shaving domes, etc. when all of a sudden, the flashlight just stopped giving any light, other than the indicator under the switch that was functioning properly.. Who knows, maybe I've shorted something out on the MCPCB when swapping the last emitter before it died.. :| I wouldn't think ESD might've caused it to die, especially after eventually finding out what the damage was.

Basically, the light would only output 2.3V on the emitter's wires and not even changing that value with stepping up or down. I also don't think this happened because of no load being present at the terminals, I don't think a boost driver would burn out without a load (the emitter)

Thanks Makner for the stupid ammount of threadlocker, one broken strap wrench and some good minutes of cooking the thing on the hot plate (until the anodizing got brownish at the base) later, I've got the body unscrewed from the business end and gained access to the otherwise "forever captive" driver. What I've found was the current sensing resistor, a puny SMD 0.03 Ohm I think 100mW ~ 125mW - 1.55mm x 0.85mm, got completely shot, thus I've tried measuring it and of course, it was not displaying any value at all. Who even puts an SMD that small as a current sensing component in a flashlight with a nearly 20W emitter.. (XHP50.2) ?

My problem now is that I don't know where I could find such a resistor without buying a whole reel of 500 or so and hopefully faster than a month..

Also, for the more experienced flashaholics around here, that are playing with drivers on a regular basis, would you assume that swapping only that current sensing resistor might actually fix the driver, or should that resistor popped, it must've took any other number of components along with it.. ? I'm thinking about leaving an open circuit behind it, might've affected something else. Driver being a boost circuit, as the emitter's MCPCB it's configured as 12V.

And here are some pics I took after getting the driver out of it's jail:

The small "R10" marked resistor appears to be blown and measuring it confirms an open circuit. Also no other components are looking like they took any damage, well, looks can be deceiving..

The blob of solder on one end of the small resistor was where the positive terminal was soldered, which I've removed for the sake of clearance around the component in cause (component that since, has been removed from the PCB - and got lost.. )

2

I don’t know if I can help you fix it but I’ll give you what I know.
It’s using a MP3429 Boost ic, datasheet here. https://www.monolithicpower.com/pub/media/document/MP3429_r1.0.pdf
I don’t think changing the sense resistor will fix it but it’s worth a shot to try.
More than likely it’s the MP3429 that has blown or could be a fet or a opamp if it even uses one. I can’t see all the components.
This driver loneoceans created (The GXB172) was based off the MP3429 here. [ GXB172 - 50W Single Cell 17mm Boost Driver! ]
Here in the states I use Arrow for my electronic needs. Cheap with free overnight shipping. Other members have reported them shipping outside the United States but I cannot comment any more than that about international shipping. Might be worth a try though.
https://www.arrow.com/en/products/search?q=0603%20resistor&prodLine=Resistor%20Fixed%20Single-Surface%20Mount&promoGroupLevel=pl&filters=Resistance+Value:30m;In+Stock:Yes;
You can also use code NEW19 for new customers gives 10% off.

3

Yes, get a new smd resistor from Arrow, I get free shipping to Germany. Grab an MP3429 as well, they kill themselves pretty often.

Hope that gets your driver working again.

4

Hi guys and thanks for the valuable info.

While I'll try first to see about that resistor and it'll probably take a while for me to grab one or just a few, as I really have nothing to do with them other than the one, I'll also try to order one of the MP3429 boost IC's and maybe even the other active components that are residing on the main PCB - that is if I'd only know what to order.. One of them would be another IC with just 3 pins, looking like a transistor and it's the one just near the blown resistor, the marking on it being "109", and it's PCB component naming being "U3". The other active component would be a FET (?) "7423 / BA6S1L" (8 PIN - judging by the PCB it's 4 pins as one top / 3 pins as one bottom + 1 pin bottom) PCB marking "Q1". And lastly, probably the MCU, "T44 / AHB / 18V" PCB marking "U1", but that's probably irrelevant without the flashlight's FW BIN and a programmer.. There are some other small IC's, but I think those only have to do with charging.

Anyways, given how.. "fragile" this driver looks and my limited resources, I wouldn't stay too far away from the idea of retrofitting a completely new driver and if required, new emitter inside this newly cleared host..

I know the options would be kinda limited given the side switch design, but I think it would be easier to say buy a Sofirn driver, as you can at least buy one.. and fit it inside. Maybe a C8G driver and a brass ring adapter..

I don't know, I'm open to ideas if the original driver would turn out to be a no go.

5

The “109” is not a transistor (it would be marked with a Q then, U stands for an ic), it’s a high-side current sense ic, in this case the ZXCT1009.
“7423” is the p-channel mosfet AON7423, looks like it’s just for battery polarity protection.
The mcu is an attiny44, but sadly with this package, you won’t be able to swap that with an attiny85 for Narsil or Anduril.

It’s up to you what you’re doing with this driver. I would buy two sense resistors (one as spare) and replace the burnt one, since they’re less than 50ct each, so if the driver won’t work with a new resistor, it wouldn’t be much money spent on it.

6

the resistor can be rated for up to 0.5W in that package, current sense resistors are usually different than normal resistors in respect what they can burn of heat

so LED 6V 4A probably
P=R*I²=0.03*5*5=0.48W so it can be within specs if they got 0.5W ones which are pretty rare

But yes I would rather use 0805 or 1206 for current sense resistor

7

You might be able to fit a 0805. If your sticking to a 0603 just use two 60mohms stacked. Two in parallel will give you half the resistance (30mohm) and double the power handling.

8

power rating on paper, the power trating is only valid if the copper traces around are thick and wide enough, stacking 2, 3 or more wont give you a linear increased power rating
it needs to be a shunt which is build to get very hot not standard resistors

9

Hi again everyone. Very much useful info in a short period of time :)

I think I'm going to start by ordering the following components:

- two of the originally used 30 mOhms 0603's (one as spare)

- 4 of the 60 mOhms 0603's (2 "pairs")

- 2 of the 30 mOhms 0805's (one as spare)

- 2 of the 30 mOhms 1206's (one as spare)

- 2 of the ZXCT1009 current sense IC (thanks Schoki for the actual component naming and function)

- 2 of the MP3429 Boost IC (hopefully none of them would be needed tho)

Also I wouldn't go as far as thinking I could swap the MCU for any reasons or purpose as I don't have the required tools or skills set to flash an AtTiny.

EDIT: Btw, forgot to ask, what would your recommendation be between the "thick film" and "metal strip" for the current sensing resistor ?

10

the thing is you buy current sense resistor not just thick film or metal strip
very high power rated ones are made from solid resistance metal alloy bond on bothe end with solid copper
and then laser or CNC trimmed to match the resistance

https://www.mouser.de/Passive-Components/Resistors/Current-Sense-Resistors/Current-Sense-Resistors-SMD/\_/N-7fjcgZ1yzvvqx?P=1z0vjvmZ1z0wljoZ1yzmou0Z1yzbppy
dont wonder they are not cheap

11

Lexel is right current sense resistor are better but usually cost a lot more. I have stacked cheaper resistors several times without any problems. This driver only came with a single of which type I don’t know but being from China I would assume the cheapest type. I have used the cheaper type on the GXB172 many times without problems.

12

Thanks for the reply.

Why I was asking about the two types it's because see attached pictures:

Apparently current sensing resistors come in both of these types, just the highest powered rated which it's 1/3W seems to be only in thick film "flavour".

So, should I look for something else basically ? Or maybe the thick film is actually what you were describing in your reply ?

Thanks.

13

Well.. Arrow seems to be a bust for me, they're requiring a VAT ID at registration, maybe it has to do with the location, idk.. I'll have to find something local hopefully.

14

Well, apparently I'm a lucky son of a gun! Yay..

I haven't had the patience to take any pictures of anything before everything was back packed inside the host and snugly fit because I didn't had the means to test the driver outside the host..

I wasn't actually expecting it, but.. to my surprise, it worked from the first try so I left it at that because I'm just lazy like that :| It was just a matter of swapping in the new current sensing resistor and that was it!

Also, lucky me, I haven't even found the other components, (well, not locally that is) other than the ZXCT1009 current sensing IC and that was also very cheap.

So, finally ended up with only spending some change on 10 resistors and 5 of the ZXCT1009 IC's, the minimum amount that I could find to buy. Happy days!

Resistor was a ROHM UCR03EWPFSR030 (UCR Series, 0603 [1608 Metric], 250 mW, ± 1%, Thick Film) Seems to have done the job ok so far - hopefully it'll break the 48h barrier record that the original lasted :))

Thanks everyone for all the info and the fast replies once more.

[EDIT]

Apparently somewhere under 48 hours it's the lifetime of this driver.. :|

Haven't actually used the flashlight for more than a few times for a brief minute or two, but last night I took it out for a bit of testing and wanted to test the turbo step-down didn't lasted 3 minutes overall.

It started by giving some short barely noticeable interruptions, or "brownouts" idk how to call them, then it started doing it more often and lasting longer, much more visible.

At first I thought it was just how this driver was stepping down, but soon it just got in a "moonlight state" and just stood there - although I could still see that changing modes was working, including the strobe modes, etc. it just was at a very dim brightness - so I thought, maybe, just maybe it's a dead battery and this might be the protection kicking in - still the side switch LED's were still blue, not purple and definitely not red.

So, just in case I've switched the battery with a full one - no change... Got the driver out and held it with the bare led on top of the body tube with the battery so I could test it out of the flashlight. For a few brief moments the led would light up normally, at full brightness, but then it got back to that "moonlight state" reduced brightness again.. I wonder if that resistor would be to blame again.. everything started by trying to see how long the Turbo would last until stepping down. Maybe 250mW it's just not powerful enough.

[EDIT]

Swapped another resistor in and the 109 IC - went well for a second or two and then got back to the low brightness state again.. Could it be the Boost IC ?

Also calculated the power that would fall on that current sensing resistor.. It would be around 0.0075W per the 0.03ohm - so.. much under the rated spec of 250mW

15

Just a quick update:

Apparently it's the last emitter that I've swapped in on the MCPCB (also don't know if the fact that the MCPCB it's aluminum really "helps".. )

Just turned on the bare driver with the led attached to it and lightly pressed with my thumb on the LED's dome - while keeping the pressure on it, it would light normally, Yey!..

Hopefully I'll just need to swap another emitter in place and hope for the best.. again. For some reason a bond wire in the emitter must've just burned.. :|

16

I have had the same thing happen when I had a bad reflow connection. I reflowed the led on myself and apparently wasn’t soldered properly. The light ran awhile then became hot and bam into moonlight it went. I could push down on the dome and back to high it go until I let off. I reflowed the led again and everything went back to normal.
Vestureofblood has a video that I used as a guide and following his method I haven’t had a problem since.

17

Hi again,

Thanks for the link, already seen the video and few others lately. I did reflow the led last night and it's working fine so far, few good minutes on turbo and hasn't blinked once. I guess it was just a bad reflow.

Regards.