Attention Electronics Experts: L&M Urban

So, I have this L&M Urban that is probably five or six years old and well out of warranty. It has gotten a lot of use and recently died in an odd way -- with sporadic indicator flashes but no light. I tried the usual protocols for getting it out of safety/sleep mode, but still no light.

I figured the battery had died, so I got a nice replacement 18650 cell, took the light apart, pulled the battery, carefully removed the solder tabs holding the protection circuit (spot welded), soldered those on to the new battery, plugged the tiny lead plug back into the circuit board -- and the same old problems. Basically I did this: https://www.youtube.com/watch?v=ZJaI...nel=SamuelEgli

Note that L&M is not doing repairs during COVID -- just offering discounts on new lights, which is not what I wanted. Anyway, I went to even greater efforts to remove the little 3/4" square PC board/LED bulb from the light (no easy feat) to see if anything came unsoldered. There was nothing obvious.

But poking around one of the little chips (maybe 2mm square with what looks like four leads under a magnifying glass) -- I got the light to come on (and about blinded myself). I figured I'd just shorted something and that it did not indicate something that could be fixed with a solder, assuming I could get my iron on that tiny little lead. I have no idea what this little chip does. It is not adjacent to the power or switch, and I don't know how it fits into the circuit. My question is would something like this be repairable or is it just junk. Does making the light come on indicate a problem with a tiny solder, or is it just shorting around this little controller and that there is a problem with the chip. Nothing looks loose, and I'm thinking that one of the tiny chips just died. That light gets super hot.

-- Jay Beattie.

On Mon, 18 Jan 2021 18:38:27 -0800 (PST), jbeattie
wrote:

So, I have this L&M Urban that is probably five or six years
old and well out of warranty.

There are various Light and Motion Urban light models. There are
Urban 350, 500, 550, 800, 1000, etc. Whatcha got? Doesn't seem to be
in their current offerings:
https://lightandmotion.com/collections/urban-cycling
https://www.google.com/search?q=light+and+motion+urban&tbm=isch

It has gotten a lot of use and recently died in an odd way
-- with sporadic indicator flashes but no light. I tried
the usual protocols for getting it out of safety/sleep mode,
but still no light.

Battery is probably dead or dying. Find a DVM (digital volt meter),
tear it apart, and measure the battery voltage after charging. A good
battery should read 4.1 or 4.2 volts. A total dead battery will read
less than 3.0 volts. Typical is anything between 3.5 and 3.9 volts.

Unfortunately, there are all kinds of other failures that might have
similar symptoms. The PWM (pulse width modulator) that controls the
brightness and turns the unit on/off might have died. For lights that
operate in the rain, water might have leaked inside and rotted out
some copper traces. Hard to tell from 700 miles away.

I figured the battery had died, so I got a nice replacement 18650
cell, took the light apart, pulled the battery, carefully removed
the solder tabs holding the protection circuit (spot welded),
soldered those on to the new battery, plugged the tiny lead plug
back into the circuit board -- and the same old problems.

Are you sure that the new battery is any good. I've bought cheap
18650 cells on eBay that lasted about 5 minutes and then died. Others
were dead on arrival. Test the cell in a LiIon flashlight to make
sure it's functional.

Basically I did this:
https://www.youtube.com/watch?v=ZJaI...nel=SamuelEgli

This is a slightly better video:
"Lights & Motion Urban battery replacement"
https://www.youtube.com/watch?v=hoYQrzQtDJc

What I was looking for is a decent photo of the COB (chip on board)
also known as the PCB (printed circuit board) or the "controller". My
crystal ball requires some minimal information on what electronic
components are on the COB in order to make a determination. Did you
take any photos when you had it apart? Something like this would be
helpful:
http://www.learnbydestroying.com/jeffl/pics/bicycles/Cygolite%20Streak%20280/index.html
What I usually find is something like this:
https://www.walmart.com/ip/17mm-1400mA-5-Mode-Memory-Regulated-LED-Driver-Circuit-Board-for-Flashlight/991091147
The AMC7135 chips are current regulator chips that go between the
battery and the LED(s). They provide a constant current, and
therefore a constant brightness, to the LED's so that they don't vary
in brightness with battery charge and condition:
https://www.electroschematics.com/wp-content/uploads/2016/04/acm7135-datasheet.pdf
The larger 8 pin chips is the PWM generator and controller. Depending
on the number of LED's and the power of your light, you'll probably
see anywhere between one and four 7135 chips depending on total
current draw, not the number of LED's.

Both videos don't show the COB so I can't tell what is in your light.

Note that L&M is not doing repairs during COVID -- just offering
discounts on new lights, which is not what I wanted. Anyway,
I went to even greater efforts to remove the little 3/4" square
PC board/LED bulb from the light (no easy feat) to see if anything
came unsoldered. There was nothing obvious.

Look for a darkened PC board on both sides of the COB. That's what's
getting hot. My guess(tm) is the AMC7135 chips, which incidentally
are usually all wired in parallel. However, replacing the 7135 chips
is not going to fix the light because the problem is probably caused
by the controller not delivering a fast rise/fall time waveform, which
is required to prevent the 7135 chips from dissipating power and
getting hot.

But poking around one of the little chips (maybe 2mm square with
what looks like four leads under a magnifying glass) -- I got the
light to come on (and about blinded myself). I figured I'd just
shorted something and that it did not indicate something that
could be fixed with a solder, assuming I could get my iron on
that tiny little lead. I have no idea what this little chip does.

The chip is probably a 7135 or an equivalent. It's what controls the
current to the LED(s). What you did was either short out the 7135 or
bridge a broken trace on the PCB. Find a flashlight and shine it
THROUGH the PCB. If the board isn't covered with protective glop, you
should be able to see broken traces.

It is not adjacent to the power or switch, and I don't know how
it fits into the circuit. My question is would something like
this be repairable or is it just junk.

I don't know. Too many unknowns and not enough information. A
schematic would be great, but probably unavailable. An exact model
number would be reassuring. Photos will certainly help.

I lied. I just found disassembly instructions and internal photos.
However, they're all useless:
https://www.google.com/search?q=light+and+motion+urban+disassembly&tbm=is ch
https://www.youtube.com/watch?v=mlhlZSAcXOg (out of focus)
https://www.youtube.com/watch?v=oL9NxLQKm-k (PCB components not
visible)


Does making the light
come on indicate a problem with a tiny solder, or is it just
shorting around this little controller and that there is a
problem with the chip.

I don't know. Making the light com on indicates that the LED and
perhaps the battery MIGHT be working. If the LED is abnormally too
bright, then the 7135 current regulators are not doing their job and
are probably shorted. However, if that were true, then the LED should
have gone to full brightness as soon as the battery was inserted or
the on/off button pushed. Something else is going on but I can't
guess without more info.

Nothing looks loose, and I'm thinking that one of the tiny chips
just died.

Dunno. Do you have access to a fairly low power binocular microscope?
Something like this:
http://www.learnbydestroying.com/jeffl/pics/microscopes/Olympus%20SZ30/SZ30-01.jpg
Look for tiny bubbles or volcanoes on top of the chips, broken traces,
corrosion damage, bad connections, etc.

That light gets super hot.

If that's true, the one of the 7135 chips is shorted. LED's normally
get hot, but not super hot.

Good luck.

--
Jeff Liebermann
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Mon, 18 Jan 2021 18:38:27 -0800 (PST), jbeattie wrote:

So, I have this L&M Urban that is probably five or six years
old and well out of warranty.

Toldja to get Frank's increasingly rare and classic Californian Sharkoculus!

There are various Light and Motion Urban light models. There are
Urban 350, 500, 550, 800, 1000, etc. Whatcha got? Doesn't seem to be
in their current offerings:
https://lightandmotion.com/collections/urban-cycling
https://www.google.com/search?q=light+and+motion+urban&tbm=isch

gg says he has the 800.

Good luck.

Thanks for the analysis. I wonder if Jay will learn by destroying and save
the lamp ... or if he just found a brilliant means to burn down his garage
in accordance with mostly peaceful January 20th celebrations.

On 1/19/2021 5:03 AM, Sepp Ruf wrote:
Jeff Liebermann wrote:
On Mon, 18 Jan 2021 18:38:27 -0800 (PST), jbeattie wrote:

So, I have this L&M Urban that is probably five or six years
old and well out of warranty.

Toldja to get Frank's increasingly rare and classic Californian Sharkoculus!

It's still here, still for sale. It's now got a couple tiny cosmetic
scratches, but otherwise good as new.

--
- Frank Krygowski

On Tuesday, January 19, 2021 at 2:03:32 AM UTC-8, Sepp Ruf wrote:
Jeff Liebermann wrote:
On Mon, 18 Jan 2021 18:38:27 -0800 (PST), jbeattie wrote:

So, I have this L&M Urban that is probably five or six years
old and well out of warranty.
Toldja to get Frank's increasingly rare and classic Californian Sharkoculus!
There are various Light and Motion Urban light models. There are
Urban 350, 500, 550, 800, 1000, etc. Whatcha got? Doesn't seem to be
in their current offerings:
https://lightandmotion.com/collections/urban-cycling
https://www.google.com/search?q=light+and+motion+urban&tbm=isch
gg says he has the 800.

Good luck.

Thanks for the analysis. I wonder if Jay will learn by destroying and save
the lamp ... or if he just found a brilliant means to burn down his garage
in accordance with mostly peaceful January 20th celebrations.

I was playing with it before work, and beating on the tiny controller made some of the function lights work which may indicate a bad trace or solder somewhere, but I'm too blind and shaky to solder something the size of an ant leg -- and I'm not going to go out and buy some home micro-surgery suite just to fix that light. The back of the chip is coated, so you can't see the traces. The battery is good -- and measures above 4.4V. And I already got a replacement on sale at Western Bikeworks even before buying the battery, so no light from Frank -- sorry Frank. I'll take one more shot at it but probably just keep it for parts. I'm also going to see if L&M will sell me a COB. I need to fix the carb on my leaf blower, which will take precedence. Then I need to clean my muddy bikes. I want them nice for the inauguration parade in my driveway.

-- Jay Beattie.

On 1/18/2021 6:38 PM, jbeattie wrote:
So, I have this L&M Urban that is probably five or six years old and well out of warranty. It has gotten a lot of use and recently died in an odd way -- with sporadic indicator flashes but no light. I tried the usual protocols for getting it out of safety/sleep mode, but still no light.

I figured the battery had died, so I got a nice replacement 18650 cell, took the light apart, pulled the battery, carefully removed the solder tabs holding the protection circuit (spot welded), soldered those on to the new battery, plugged the tiny lead plug back into the circuit board -- and the same old problems. Basically I did this: https://www.youtube.com/watch?v=ZJaI...nel=SamuelEgli

Note that L&M is not doing repairs during COVID -- just offering discounts on new lights, which is not what I wanted. Anyway, I went to even greater efforts to remove the little 3/4" square PC board/LED bulb from the light (no easy feat) to see if anything came unsoldered. There was nothing obvious.

But poking around one of the little chips (maybe 2mm square with what looks like four leads under a magnifying glass) -- I got the light to come on (and about blinded myself). I figured I'd just shorted something and that it did not indicate something that could be fixed with a solder, assuming I could get my iron on that tiny little lead. I have no idea what this little chip does. It is not adjacent to the power or switch, and I don't know how it fits into the circuit. My question is would something like this be repairable or is it just junk. Does making the light come on indicate a problem with a tiny solder, or is it just shorting around this little controller and that there is a problem with the chip. Nothing looks loose, and I'm thinking that one of the tiny chips just died. That light gets super hot.

-- Jay Beattie.

Give up.

Buy the Gaciron V9D-1800. https://gaciron.aliexpress.com/store/2906009.

The thing I really like about this light is that the DRL is not a
strobe, it's "breathe mode." The extra mounting brackets are pretty
inexpensive as well so you can stick one on each bicycle.

On Tuesday, January 19, 2021 at 1:25:05 PM UTC-8, sms wrote:
On 1/18/2021 6:38 PM, jbeattie wrote:
So, I have this L&M Urban that is probably five or six years old and well out of warranty. It has gotten a lot of use and recently died in an odd way -- with sporadic indicator flashes but no light. I tried the usual protocols for getting it out of safety/sleep mode, but still no light.

I figured the battery had died, so I got a nice replacement 18650 cell, took the light apart, pulled the battery, carefully removed the solder tabs holding the protection circuit (spot welded), soldered those on to the new battery, plugged the tiny lead plug back into the circuit board -- and the same old problems. Basically I did this: https://www.youtube.com/watch?v=ZJaI...nel=SamuelEgli

Note that L&M is not doing repairs during COVID -- just offering discounts on new lights, which is not what I wanted. Anyway, I went to even greater efforts to remove the little 3/4" square PC board/LED bulb from the light (no easy feat) to see if anything came unsoldered. There was nothing obvious.

But poking around one of the little chips (maybe 2mm square with what looks like four leads under a magnifying glass) -- I got the light to come on (and about blinded myself). I figured I'd just shorted something and that it did not indicate something that could be fixed with a solder, assuming I could get my iron on that tiny little lead. I have no idea what this little chip does. It is not adjacent to the power or switch, and I don't know how it fits into the circuit. My question is would something like this be repairable or is it just junk. Does making the light come on indicate a problem with a tiny solder, or is it just shorting around this little controller and that there is a problem with the chip. Nothing looks loose, and I'm thinking that one of the tiny chips just died. That light gets super hot.

-- Jay Beattie.
Give up.

Buy the Gaciron V9D-1800. https://gaciron.aliexpress.com/store/2906009.

The thing I really like about this light is that the DRL is not a
strobe, it's "breathe mode." The extra mounting brackets are pretty
inexpensive as well so you can stick one on each bicycle.

BUT it also comes with an 1800 lumen strobe -- for pure punishment. I'll get two and make people regret driving. Actually, I've felt like retaliating lately. Is it my imagination or have low-beams become high-beams in the last ten years?

Also, do people actually buy from AliExpress and Alibaba? It looks so sketchy.

-- Jay Beattie.

On 1/19/2021 7:15 PM, jbeattie wrote:
On Tuesday, January 19, 2021 at 1:25:05 PM UTC-8, sms wrote:
On 1/18/2021 6:38 PM, jbeattie wrote:
So, I have this L&M Urban that is probably five or six years old and well out of warranty. It has gotten a lot of use and recently died in an odd way -- with sporadic indicator flashes but no light. I tried the usual protocols for getting it out of safety/sleep mode, but still no light.

I figured the battery had died, so I got a nice replacement 18650 cell, took the light apart, pulled the battery, carefully removed the solder tabs holding the protection circuit (spot welded), soldered those on to the new battery, plugged the tiny lead plug back into the circuit board -- and the same old problems. Basically I did this: https://www.youtube.com/watch?v=ZJaI...nel=SamuelEgli

Note that L&M is not doing repairs during COVID -- just offering discounts on new lights, which is not what I wanted. Anyway, I went to even greater efforts to remove the little 3/4" square PC board/LED bulb from the light (no easy feat) to see if anything came unsoldered. There was nothing obvious.

But poking around one of the little chips (maybe 2mm square with what looks like four leads under a magnifying glass) -- I got the light to come on (and about blinded myself). I figured I'd just shorted something and that it did not indicate something that could be fixed with a solder, assuming I could get my iron on that tiny little lead. I have no idea what this little chip does. It is not adjacent to the power or switch, and I don't know how it fits into the circuit. My question is would something like this be repairable or is it just junk. Does making the light come on indicate a problem with a tiny solder, or is it just shorting around this little controller and that there is a problem with the chip. Nothing looks loose, and I'm thinking that one of the tiny chips just died. That light gets super hot.

-- Jay Beattie.
Give up.

Buy the Gaciron V9D-1800. https://gaciron.aliexpress.com/store/2906009.

The thing I really like about this light is that the DRL is not a
strobe, it's "breathe mode." The extra mounting brackets are pretty
inexpensive as well so you can stick one on each bicycle.

BUT it also comes with an 1800 lumen strobe -- for pure punishment. I'll get two and make people regret driving. Actually, I've felt like retaliating lately. Is it my imagination or have low-beams become high-beams in the last ten years?

Also, do people actually buy from AliExpress and Alibaba? It looks so sketchy.

-- Jay Beattie.


Winnie the Pooh is building a Navy and those are two of his
funding arms. Make your own choice.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 1/19/2021 6:32 PM, AMuzi wrote:

snip

Winnie the Pooh is building a Navy and those are two of his funding
arms. Make your own choice.

LOL, instead buy L&M lights, made in the Philippines, and support
Rodrigo Duterte instead of Ma Xingrui.

On 1/19/2021 2:59 PM, jbeattie wrote:
I need to fix the carb on my leaf blower, which will take precedence.

OK, then a possible carb tip.

My chainsaw was getting very fussy about starting. Accessing the carb
was tough; it was really buried, but I dismantled the saw to inspect the
carb and fuel lines. I found nothing wrong, reassembled everything,
cranked each of the two mixture screws in (carefully counting turns)
then back out the same amount, and pulled the cord. It started right up.

Next time I'll run those screws in and back out before trying anything
else. I suspect doing that was more valuable than all the other work I did.


--
- Frank Krygowski