Problem with a Jayrob kit: XJ-A140 diode kind of LEDed ?

Hi there.
I bought a few weeks ago a Jayrob 18500 kit with a microboost set at 700mA and a XJ-A140 from daguin (well, two as I fried one before I received the kit :cryyy: ). The laser worked perfectly until yesterday night.
I don't know what happened, but when I fired it I noticed that the power seemed lower than usual, and a few seconds later it dropped to ~20mW (I have no LPM, this is an estimation ). I thought the battery might be empty, so I swapped it with another one, but the problem was still there: ~300-400mW for a short time and then a drop to ~20mW .
I thought the other battery might be empty too, so I charged both during the night, and this morning, I tried again: same thing :cryyy: . I have just checked and the driver seems to work: I mesured a 700mA current, as expected. That's why I think the diode is dead, but why ?
I removed the lens and tested again, and the result is odd. At first everything seems to be ok (ie: a normal patern for a multimode diode), and then the two "bars" next to the middle one start to move and end by merging with the middle one. Then, half a second later, the multimode patten completely disappears: the diode seems to have LEDed ... But it has not really, because if I turn the laser off and on a few seconds later, I can see the multimode pattern for a short time, and then noting ...

I haven't opened the laser since I soldered the diode (except to change the batteries ) and I haven't dropped it ... Since 700mA seemed to be a safe current, I expected the diode to live much longer. Do you have any idea on what happened ?

Re: Problem with a Jaybob kit: XJ-A140 diode kind of LEDed ?

Maybe the diode has a loose fit in the heatsink?
When a diode gets hot, the mode will change.
Only thing I can think of.

Re: Problem with a Jaybob kit: XJ-A140 diode kind of LEDed ?

Could you desoldering the LD and test microboost with testload and mesure the output mA?
there is a long wires between battery and microboost?

I think heatsinking is quite good because when the laser worked I could feel the host become warm. And don't you trust Jayrob's copper heatsink ? :na: JK

I have already unsoldered one pin of the diode to measure the current going through it. I measured a constant 700mA (well I believe it's constant because I have a crappy DMM), even when the diode seemed to output 20mW.

The wires are not very long, and I'm pretty sure they didn't touch each other, as I didn't twist the heatsink while puting everything together.

I made two videos to show the problem. The first shows the diode with the lens, and the second is without the lens. The red and black wires are going to the DMM to measure the current.



Edit: On the videos, the phenomenon is faster than what I described, it seems to speed up as the diode gets warmer, so maybe CrazyMonkey is right: it might be a heat issue, but I believe I mounted the diode the right way and it fits the heatsink well ...

clempar55 said:

I think heatsinking is quite good because when the laser worked I could feel the host become warm. And don't you trust Jayrob's copper heatsink ? :na: JK

I have already unsoldered one pin of the diode to measure the current going through it. I measured a constant 700mA (well I believe it's constant because I have a crappy DMM), even when the diode seemed to output 20mW.

The wires are not very long, and I'm pretty sure they didn't touch each other, as I didn't twist the heatsink while puting everything together.

I made two videos to show the problem. The first shows the diode with the lens, and the second is without the lens. The red and black wires are going to the DMM to measure the current.



Edit: On the videos, the phenomenon is faster than what I described, it seems to speed up as the diode gets warmer, so maybe CrazyMonkey is right: it might be a heat issue, but I believe I mounted the diode the right way and it fits the heatsink well ...

Click to expand...

This looks like a power supply problem

Replace the battery and try it with a new quality battery. It is possible to have two batteries go bad at once.

It is also possible that it is the charger that has failed.

If a new battery does not fix it, go through and clean up ALL of the contacts (battery, solder, spring, threads, etc.) also looking for possible shorts

Finally, replace the driver,

Peace,
dave

listen to dave. i have experienced exactly this. bad charger and bad batts on 2 seperate occasions. and some times batts will read as fully charged but contain no current. also i have had batts read zero volts but charge up and be perfectly fine and and still alive to this day.

michael

Check the current and voltage at the battery end and see
if they are stable...
If not.. the Batteries are at fault... IMO

Jerry

I've had cheap 18650 batteries fail me at even less than 700mA's...

It's worth spending the extra money on an AW battery for a high current build:
AW 18650 Protected 2600 mAh Rechargeable Lithium Battery - New Version

Try that before messing with your laser any more. It's most likely the battery as was mentioned...

Well I have no new batteries to test the laser with, but I don't think they are the main problem, because I measured the current passing through the diode and it is really 700mA. I also tried with another load ( the cree LED that comes with the kit + a resistor), the current is still 700mA, and the cree LED is working flawlessly. I will try to borrow another DMM to confirm (because mine is not great), but in my opinion the diode is the main problem. Could it be harmed by a driver issue whose origin may be a bad battery ?

I also forgot to mention that when I received the kit, the tail switch seemed to be a bit loose, indeed I could unscrew it by hand. When I noticed it I unscrewed it and replaced the cap with a GITD one ( I think you can see it on the videos), and I used a small tool to screw it back more tight. Could a loose connection have harmed the driver and provoked a current spike ? Beacause I used the laser a few times before realising it was loose ...


Anyway, thank you for your answers, I will try to borrow another DMM and maybe to hook the diode to a PSU+resistor to check if it might still be alive. If it is, I will buy new batteries, otherwise, I will see what to do ...

If the switch had a connection issue, it would not harm anything. It's just like turning it off and on...

Sometimes a battery can show good voltage, but when you put a load on it, it will fail even with a full charge.

Not sure how you tested for current with the diode connected, because in order to do this properly, you would have to have your DMM in series on the positive feed between your driver and your diode.

Maybe you measured improperly??

The symptoms you are having, point to an insufficient power supply as was mentioned by others.

I would first try a quality AW battery before trying anything else. If it turns out that there is a problem with the diode, it's not like you wasted money on the battery. Which you will need anyway...

I found in some flash light host if you screw the tall cap innereds witch hold the glow in the dark tall cap and switch mechanism tighter and like you said you screwed it tighter after putting in a glow in the dark tale cap. It could be that you tightened it to tight and it is not making a good connection.

(This is just an example i do not have that same flashlight host you have but i believe it has a similar setup to this host.)
Heres an example of me pointing to the metal ring on this flashlight tall cap that you tightened.


Here iam pointing to that part of the host that has to make contact with the part that iam pointing in the picture above.


If those 2 are not connected your host will not make a good connection or just wont work. Try unscrewing it a little until when you screw the tall cap to the body you can feel those 2 parts i pointed out are touching.

I have had this problem several times with some china DX flashlight.
Let me know if this fixed it.

If not then i dont know do what Dave and Jay said.

Actually, the bare metal threads should be making enough contact between the cap and the host, but sometimes there are connection issues between the contact point on the switch, and the cap/retainer ring...

Different switch assemblies make contact to the cap differently. Most are a simple thing to see just how the contact is made.

But once again, the symptoms you are describing, do not sound like a switch issue...

Driver is falling out of regulation... def. power supply problem. If you have a PSU sett it to 4.5 volts just make sure it able to produce enough current. Some of those cheaper ones are limited in the current department.

Yes, indeed now the switch is not an issue, because I tested with a wire to make contact between the host and the battery, and the symptoms are the same.
But when I mentioned the switch I wondered if a loose connection could make like a switch that opens and closes very fast (faster than someone using it), which could have harmed the driver. I haven't got its shematics but since it has a coil, switching the power very fast could induce an unwanted "boost" effect or a voltage spike that could have harmed the diode. I have no clue if it's possible, it was just a suggestion ...

Sometimes a battery can show good voltage, but when you put a load on it, it will fail even with a full charge.

Not sure how you tested for current with the diode connected, because in order to do this properly, you would have to have your DMM in series on the positive feed between your driver and your diode.

Maybe you measured improperly??

Click to expand...

To measure the current I unsoldered the wire going from the + driver output to the + input of the LD. Then I connected the + driver output to the +side of the DMM, and the - side of the DMM to + diode input. I believe it's correct right ?
I also measured the battery current draw (DMM between the battery and the host). I can't remember the value but it was more than 1 amp, so the battery is able to provide power to the driver ... I also tried the battery on another circuit, and the current draw was near 3 amps, so I think the battery itself is not a problem.

Anyway, I finally hooked the LD + a 2.2 ohm resistor in series to a 5V PSU (an old computer psu so it is powerful enough). The current was about 450mA, but the symptoms were exactly the same ! The multimode pattern went away after a few seconds, and the optical power droped, whereas the current remained (nearly) the same.
So maybe the batteries were an issue, but the diode had a problem too.

I said "had" because when I soldered it back to the driver (only one pin, same configuration as before with the DMM) and desesperately tested again, I think a wire connected to the DMM disconnected and then made contact again, because I could see the LD blink, and since then, there is no multimode pattern anymore. I think the driver (when disconnected) maxed to 12-13V (the value in the driver doc) and the diode got these 12V when it reconnected . Now it's completely LEDed

The problem is that I can't afford buying another LD now, so I guess I will just wait to buy another one (as well as a battery) or maybe resell the kit ...

That's a bummer...

That's why I had said earlier to not touch it until you try an AW battery. Because it is very easy to cause a cap discharge to the diode while testing. Especially if your frustrated trying to figure out what the issue could be... (but for all we know, the diode may have already been damaged)

That hurts to loose a nice diode. We all know the feeling. At least it was not too expensive...

I've killed $300 dollar diodes before. More than once... :banghead:

Clempar why don't you order a couple of LOC or PHRs to practice on first... you'll get it right, you sound like you have a pretty good start for a noob... don't give up.

A year from now you'll have a good grip on laser pointer construction and maybe a good collection as well. Don't give up! I know from experience that your close to being successful, you just have to go thru protocols such as shorting capacitors and learning more about batt. selections ect... learn from these experiances do more reading here and implement a set of building habits.

Start by stockpiling supplies and banging one build out slowly, thoughtfully, just slow down! I always try to take my time. The builds I rushed through never were as satisfying as
the one that took longer. Good luck and I'll be looking for some more of you future build success.