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HELP - noob trying to repair laser pen

tsteele93

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I ordered s laser off the buy sell and trade section of the forum and I got a "marginal" laser.

It is a red, but when I went to put batteries in it, the module popped out a little. The laser would not work.


Laser 1 by tsteele93, on Flickr

Upon closer examination, this is what I am seeing.


Laser 2 by tsteele93, on Flickr

I took the whole thing apart and here is the lens, led, module, and driver.


Laser 3 by tsteele93, on Flickr

Not sure why the negative isn't hooked to anything. Should it be against the case and case neg?

Any tips or direction would be greatly appreciated.

TIA,

ts
 
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lazeerer

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Which way did you put the batteries in.?

It appears to be case negative build. So your laser was getting the Negative input from the case to your diode.

On those pen Host tail caps they will not make contact with the Negative of the battery without some kind of magnet or spring in there. So this could possibly be why it dint work when you tried it.

Also did those batteries come with the laser.? They look protected.?

If the laser was built to be used with Non protected cells or when building was done they where using un protected cells which are shorter cells and not take into account of longer protected cells then this could be the reason why the module popped out the front.

Why dint you contact the seller before taking it apart.?
 
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rhd

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I have a couple thoughts:

1) Reds of the traditional (non 635) variety are generally case-negative. IE, you have no choice but to build case negative. So the lack of a negative wire is fine.

2) I couldn't figure out what was going on with that driver board, until I caught glance of the two silver cells you were using to power it, and realized that it's a 2x lithium ion build. Meaning that you're using ~8V to power a diode with a Vf of just 3V. This also means that it's probably using a pretty inefficient linear driver. It also explain the copper... *stuff* that I see folded on top of the driver. That IC is going to get majorly hot, majorly fast. If there's any moderate amount of current (say even 400mA), you'd be dissipating 5V x 0.4A = 2W of heat out of that IC. I'm not sure a pen build life that can handle the driver heat you'd be creating.

3) I don't see any goop on the module, meaning it wasn't put in using thermal compound.

So I see potentially major heat issues, but I think what probably killed your diode is:

4) Depending on how the setup is wired, when your module popped out, it probably opened the circuit between your driver's output and the diode input, long enough for the cap (assuming there is one, though I don't see any from these photos) to charge. Then when the module was re-inserted, it discharged across the diode, killing it.
 
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tsteele93

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I'm not certain the diode is killed. I will check. It did not come with batteries, I was told it took 10440's so I ordered those and did not know if it needed protected or not. The seller told me it would work with Li-ion, but suggested I use LiFePO4 to make the diode last longer.

I told him I couldn't find those in 10440 and he said just use Li-ion.

I assume it was case positive because there is no way the negative side of the batteries will touch the bottom of the case.

I contacted the seller through PM and he said I need to cut the plastic away from the battery so it will make contact. Maybe that is all that was wrong all along, other than using long batteries that pushed the module out?

Maybe if I put it back together with thermal adhesive and get some unprotected batteries and make sure they can touch the bottom of the case it will work.

If not, what diode should I try as a replacement?

Thanks for the tips. I think the big problem here was miscommunication between me and the seller on the batteries, I think the seller assumed I was more experienced with custom built lasers and I was assuming this was a more commercially built model with straightforward plug and play batteries.

We will see...

ts
 

tsteele93

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P.S. re-reading RHDs comments, I can't recall the exact mW that the seller was advertising and it appears that he has deleted the listing so I am unable to check for sure. But I think it was 100-150mW.

Lazeerer, I did PM the seller. But I also figured that I would take it apart and see if I could figure it out myself (with the help of the forum of course) and learn something. I found the "so you wanna build a laser" thread and learned a ton!)

I am an old man (40's ha ha) looking for a fun new hobby and I think that I would like to follow in RHD's footsteps and try to make some interesting builds as I learn more.

So I decided to treat this as an opportunity to learn something rather than a bad laser purchase. :)

ts
 

tsteele93

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One question, should I be using unprotected cells, or protected cells on a laser build? Does it make any difference other than length? Or does it affect the performance of the laser?

Thanks for helping me learn.

ts
 

lazeerer

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Hey,

So pretty much exactly what was said above.

You put the cells in the wrong way and possible you killed the laser since i don't think there is a reverse polarity protection on the driver.

Next with the tail cap. Like i mentioned above that the negative contact of a battery will not make contact with the casing inside the tail cap because there is no Spring or some kind of Nipple to make contact with the negative of the battery since its flat.

I DO NOT RECOMMEND you peal the plastic casing back alittle on your cell or cells. Just use a little magnet and that will do the trick.

Cutting the plastic casing back alittle from a protected cell cam be Extremely unsafe.

Test and see if the laser works. If its dead we can go from there.
 
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rhd

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A few more thoughts:

1) I have never seen LifePo4 10440s. That doesn't mean that they don't exist of course, but I wouldn't have a clue where to find them if they do. More importantly though, I've never seen them used on LPF. So right off the bat, my "BS" detector is in armed position. (To be clear - the BS detector is aimed at the original seller, not at you ;))

2) If the build was using a proper current-regulating driver, why would someone's choice of battery chemistry "make the diode last longer" ? A proper driver would be supplying the same current/voltage to the diode, regardless of the battery type used (within reason of course). The surplus voltage of standard lithium ion cells above the LifePo4s would simply be burned away by the driver's IC. If anything, I could actually see *some* sense in saying "use LifePo4s to make the driver last longer". I still wouldn't say that myself, but at least it wouldn't be totally counter-intuitive. So now my BS detector is cranked up to "hyper mode" ;)

3) If the diode is getting the negative feed from the host wall, then I'm assuming (and based on the photo, it appears to be the case that) the driver isn't getting a negative feed from anywhere. This implies that the driver isn't using a protective cap. If it's a DDL style driver, it really should have a protective cap, even simply for driver stability.

4) This brings me to one critical question - who was the seller / builder?

What I would do?

- Ditch the driver, and either build, or buy a more appropriate one. If you want to use 2x lithium ion cells, then you could get away with soldering your own LM317 driver, with only a few parts (IC, cap, resistor). If you want to go pre-made, a RCKSTR or Groove driver would work, as would any number of ~$5 linear drivers that you could grab from OdicForce, eBay, etc.

- You'll need to know the current needs of your diode if you want to try to re-use it. So you'll need to ask the seller for that info.

- If that's a no-go, if the diode is dead, then I'd pick up an LPC-826 for < $10, and give that a shot.
 
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lazeerer

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JERK! :)

Honestly though - have you ever seen those used here on LPF? Would you ever use those?
I have never seen them used before but a member was looking for something like them for one of his green laser and that was a long time ago.

But i have never seen someone use them in a build on LPF other then what i mentioned above.

He possibly recommended to use them to try and lower the voltage so there is less heat waste.
 
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tsteele93

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I will put it all back together and see what happens. I'll let you know more then. If I truly feel like I was ripped off then I will post the forum member's name. I'm starting to feel like I wasn't intentionally ripped off, but I think that I may have been sold a pretty poor quality laser represented as nicer than it was... I'll let you know more as I get it back together.

I'm stuck helping someone migrate to a new computer tonight.

ts
 

tsteele93

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Quick check shows a load if I place the neg lead of the multimeter to the negative lead of the diode and positive lead of the multimeter to the positive lead of the diode and no load when reversed, so that is a good sign.

ts
 

rhd

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How about telling us the rough price?

Sidenote: People around here get antsy if you double-post. The STRONG preference of everyone is that you go back and edit your previous post to include new info, instead of posting a second reply.
 

lazeerer

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I will put it all back together and see what happens. I'll let you know more then. If I truly feel like I was ripped off then I will post the forum member's name. I'm starting to feel like I wasn't intentionally ripped off, but I think that I may have been sold a pretty poor quality laser represented as nicer than it was... I'll let you know more as I get it back together.

I'm stuck helping someone migrate to a new computer tonight.

ts
There are just a couple things that needed more attention thats all.

May i ask how much you paid for the laser.?

Edit:^ Beat me to it.
 
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