"Laser 301" host breakdown.

SD-Laser "301" and "303" host breakdown.

Update - 7/1/2014

I started this thread just over a year ago after a long, frustrating, and ultimately futile search for technical information concerning the Laser 301, 303, and similar laser pointers. Reading over it now, I can see that the information is very sparse and that it leaves much to be desired. Over the next few days I will be correcting that.

Expect new photos, a much more thorough host breakdown, comparison and contrasting of host variants, and general information such as thread sizes and whatnot.


Introduction: Laser "301" and "303"

If you're interested in lasers, you can't get very far into the hobby before you encounter the "301" and "303" handheld lasers. These lasers seem to be everywhere. Ebay searches involving "laser" will turn them up by the dozen, and they're sold on scores, if not hundreds of websites specializing in cheap Chinese exports. The 301 and 303 are a common sight at music festivals, block parties, and other large outdoor events as well, due to their brightness, ease of use, and low cost.

Despite being easy and fun to use, the 301/303 lasers do have frequent quality control issues and are often derided as junk by experienced builders.

I have to wonder, also, if LPF as we know it would even exist without the 301. For a lot of now-established members, myself included, the 301 was the first laser (or one of the first) that we ever owned; its low cost made the laser hobby accessible to us when it otherwise would not have been. At least a few of those members have advanced to become experts in the hobby - builders, machinists, artists.

But even though the 301 and 303 are probably the most common handheld lasers in the world, almost no information about them is publicly available. Technical info about the lasers and hosts, manufacturer info... I've spent hundreds of hours looking for it, and have found very little. I'm not the only one who is curious - we get questions about the 301/303 posted here on LPF all the time, and it's always the same questions... what lens do I need, how do I correct the focus, can I replace the diode/dpss module if it dies, etc.

Everything after this point still needs to be updated.

EDIT 6/5/14: The laser below is a 532nm DPSS laser. That is why the module looks as it does; if your 301 is just a diode laser (i.e. not DPSS) then the internals will look similar, except you will see the laser diode rather than the pre-expander lens that you see below. Direct diode lasers also have slightly different dimensions for the focusing barrel, but the general layout is the same. The host is still a PITA to work on in any case.

I couldn't find an explicit breakdown diagram for the 301's, but they are pretty common, so I decided to make my own. Hopefully the info will be helpful!

HOST BREAKDOWN:



1 - Crown, a.k.a. focusing knob.
2 - Focus barrel. The lens barrel screws into this part. The focus barrel can be unscrewed from (3) but don't bother unless you need to replace the lens. It's easy to get this part cross-threaded when re-installing it, so be careful about that.
3 - Front end outer casing
4 - Laser module. This one is DPSS but direct diodes can look similar.
5 - Main host body. The laser module is press-fit into this part. The driver is located beneath the button.
6 - Battery compartment extender. With extender in place, the laser fits one 18650 cell. With extender removed, one 16340.
7 - Tailcap and key switch. The switch may be threaded or press-fit into the tailcap.

Unscrewing (3) from (5) can be a hassle. They are screwed together very tightly, and usually there is glue/thread locker. I resorted to using channel locks to get them apart. I needed two pairs, one to grip the host body (5) and the other to rotate the front end (3). This did leave tool marks, but they aren't bad. You do need to grip the tools TIGHTLY because the anodizing is very slick. If you don't grip them tight, the tools will slide and tear up the anodizing. I will say that even with tools it did take a fair amount of force to break the parts loose. After you open the laser the first time, subsequent openings will generally be easier unless you re-glue the threads.

I tried using a strap wrench in place of channel locks; it didn't work. The host was too small and too smooth for the strap to get a good grip, and the wrench just slid. I don't recommend using a pipe wrench either - they are prone to sliding before they can establish a good grip, and that would likely tear up the anodizing.

Warning: You can power up the laser with the front end (3) removed and shine it on a wall to check the cavity output. Don't look into the exposed laser cavity while the laser is on. With the front end removed, there is nothing between your eyes and the active laser apparatus. The pump diode is IR and puts out 100's of mW. The vanadate crystal will be lasing 1064nm as well, figure another ~100mW there. Your yellow safety glasses will NOT protect you from ANY of that - with IR it will be as if the safety glasses were not even there. IR-safe glasses will have an explicit statement and O.D. rating to that effect. If yours don't, then you must assume that IR will pass through with zero attenuation - please be careful!

LENS ASSEMBLY:



Close-up of lens barrel (2) inside lens barrel housing (3) plus the tweezers I used to adjust focus. The barrel and housing are threaded. Normally the crown and lens barrel are screwed and thread-locked together and rotate as one unit. This makes the laser focusable.

The lens is plastic and is extremely delicate. Compressed air in a can is the best way to keep it clean. Anything remotely abrasive will scratch it. If crud does get on the lens and canned air doesn't remove it, I honestly don't have any good advice for you. A botched cleaning attempt is what ruined my lens and brought about this "project" in the first place. NEVER use paper of any kind to clean the lens - doing so will ruin it. Avoid touching the lens, getting anything (grease, metal particles, dust, ANYTHING) on it, don't let your tools touch it either. Spray it often with compressed air throughout the project just to be safe.

If the focus is wrong, it can be adjusted. Focus is adjusted by loosening crown threads and rotating the lens barrel relative to the crown. The tweezers fit into the small holes and make a good "driver" for rotating the lens barrel while the crown is held stationary. This is a bit of a hassle because the crown never wants to stay put once you've found the right focus. But, with a bit of finagling you can eventually get it into the right place. Apply thread-locker to hold the crown in place.

ETA: On thinking about focusing these, if one is willing to adjust the lens carrier itself, perhaps the following would be best: Remove focus knob (1) from adjuster barrel (2), leaving the lens assembly (3) installed on main host body (5). Screw adjuster barrel into lens assembly until adjuster barrel bottoms out against host body. Adjust lens carrier to set this position as focused to infinity, or whatever else you want. Then, apply a little thread-locking compound to the lens carrier's threads. Avoid getting compound on lens. Apply compound to threads at top of adjuster barrel, and reinstall the adjustment knob. Adjustment knob should be turned down until it is firmly stopped, but don't over-tighten. Allow thread-locker to cure and, unless I'm missing something, that should be foolproof every time.

The brass lens carrier itself can also be adjusted inside the focus barrel, but don't bother. It's a hassle (glued threads), it isn't necessary, and your tools come dangerously close to the lens (high risk of ruining it!).

LASER MODULE:


Close-up of the laser module. I'm pretty sure it's press-fitted into the host and probably glued as well. Chilling the module might make it easier to remove it. Would an Aixiz module fit in there? Laser 301's are cheap ($15 from Amazon, last I checked), maybe it would be worthwhile for experienced builders to buy them just for the hosts.

The 405nm units have a similar module, but there is only the laser diode. The diodes are small, probably 3.8mm. It would be interesting to see a 520nm direct green custom build.

Before and after pics:

This is the good laser cavity with bad lens (left) and its shiny new good lens (right).

Nice review! Should I ever come into one of these, I'll know just what to do!

+1 for you, sir.

I am one of those with a "Laser 301" Host that spent some time taking apart. I made the mistake of messing with the lens thinking I could make it less divergent... Lo and behold I have a more divergent laser now with little success at getting it back to how it was.

I have a very similar host and I just gave up on opening it. I knew there must have been a way to do it.
What do you thinkg in heating up part 3? I tried that with a heat gun but no real effect. Normally locktite should melt under high temperatures but it just didn't loose. I even ended up scratching the host.

3 was difficult, I did scratch the host :cryyy:. My method was 2 pairs of pliers and a butane torch (would not recommend) to very carefully weaken the glue.

I tried using heat to loosen the parts and it didn't work as well as chilling the inner joint with the computer duster. I think it's because the liquid can be directed more precisely, and it cools the metal faster than a torch or heat gun could warm it. This is important, because you want the temperature difference between (3) and (5) to be as large as possible. You have to work fast, before the temperatures have a chance to equalize.

I imagine cold would make the glue more brittle as well, and thus more breakable.

eta 6/5/14: forget the above. It does work but it's a pain in the ass and you're probably better off just using tools. Do that and save yourself the hassle. -MP

I googled "strap wrench", they do make them and I think they would make ideal tools for opening up these hosts. Unscrewing them by hand is difficult (hard to grip) and can be painful. I managed to get a nice blister on my thumb from working on this thing. eta 6/5/14: none of the strap wrenches I tried could grip the host - the host is too narrow and the anodizing too smooth. -MP

ETA 6/5/14: Ultimately, I've decided that channel locks are the best way to get these things apart. Two pairs: One to hold the host stationary, the other to rotate the front end. They do leave tool marks on the host but I don't particularly care about that. Even then, it takes some force to break the glue, and you have to grip the tools TIGHT or else they will slide on the anodizing and tear it up.

Do you by chance have a vice grip? That may help you tremendously. That way you can clamp it down (with a cloth), then apply the heating or cooling, then use a pair of pliers with a cloth, to twist it.

Every piece of my 301 came apart easily no glue in sight, except for the module. But I think something is wrong with the lens. I have not touched it yet but just looking at it I felt the proper focus method was turning that either further outward a bit or inward a tad. Then I found this thread and was like oops.

Anyway, your lens in the pics look completely different. Mine looks like it is cracked on one side and not entirely flush with the lens carrier (barrel). The lens carrier looks like the same ones you find in the Dollar store or Petco's laser cat toys. I may buy one just to get at the lens.

EDIT: Lol, never mind me, I guess you do adjust it from that little brass barrel. Not sure what you meant by setting it to infinity, but after some fiddling with now it seems to be as tight as it will get with the focus ring screwed all the way in. Now to find a thick grease to put on the inside of the Lens Barrel Holder (3) because that lens adjuster (2) seems very wobbly inside there.

Thanks for the break down... This was helpful.

SkOrPn said:

Now to find a thick grease to put on the inside of the Lens Barrel Holder (3) because that lens adjuster (2) seems very wobbly inside there.

Thanks for the break down... This was helpful.

Click to expand...

I would recommend teflon tape, if you don't mind removing the lens adjuster to put the tape on. It would be much less messy than grease. If you get grease on the lens, might as well throw that lens away and get a new one, because unless it's glass you aren't getting that lens clean

Glad the breakdown was useful, feel free to add anything that I missed, if you think it's appropriate. :beer:

Just brilliant, how did I miss the teflon tape idea? Thanks that worked perfectly...

Hey All,

I too have fallen for the SDLaser303 and think the problem is no 2 are the same, I have 3 now first one the lenz on the diode came loose tried to stick back down then burnt a hole in the plastic, 2nd one same outer shell but not as bright different focus barrel , 3rd one labels different correct spelling and feels more sturdy. Iv tried tracking them down its not easy but I got there in the end and its a massive wholesale trading company in China sure it was SDW Trading basic website but sell them minimum orders 10 it says can supply 10,000 units per month, it seems like many small company's in one co-op hence the mish mash of parts. If anyone knows where I can get the lens on diode and what type it is Plano convex bi convex I would appreciate it.

There are quite a few different focusing barrels. Among my 301's and 303's there are M8, M9, M9.5, and M10 threads, all 0.5mm pitch. These days, the hosts are more consistent than they used to be. They seem to have settled on the 303 design as a standard of sorts. This means an M9x0.5 lens barrel (532nm dpss often use M8x0.5, however), aluminum heatsink to mount a 12mm module in the host, and usually an M12x0.5 thread at the front for a diffraction "star" cap.

You can generally interchange parts although different thread and other tolerances sometimes cause problems.

I have two lasers with the 303 host, one 780nm and one 532nm and I have some observations to do.

The host is a unique piece, I think the module is glued into the host, in the 780nm that originally was 405nm, I only was able to lock the module inside the host using glue.

To take the laser module off, I need to remove piece #1, then, remove the lens and with a screw or other thing and a hammer, push the module until it goes off.



This ferrite pipe visible here is a single piece that goes all the length of the laser, only having a hole for the button, the module slides into this pipe freely:


Here is the pipe empty, without the module:


Here without the piece #1 and without the module:


Here the laser module:


On my 532nm laser, I can't see any way to get part #3 out of #5, looks like a single piece.

Separating part #3 from part #5?

#3 is the front end, it should screw onto #5 the main host body.

The joint is located right at the bottom of the silver danger label, at the bottom of that last groove there, the one closest to the button. How much glue have you encountered so far in taking apart the laser? Mine had a ridiculous amount of glue and it made it a lot harder to take apart. If there is glue you can melt it with a butane lighter, just heat up the host metal until it's too hot too touch. At that point I use channel locks or large pliers to unscrew the front end while the glue is molten.

I had my 301's quite a while before I realized there was a screw joint there, until then I thought the host was a single piece. Since you have the focusing ring off, you can take the whole front end apart once it's removed from the host.

To take the laser module off, I need to remove piece #1, then, remove the lens and with a screw or other thing and a hammer, push the module until it goes off.

Click to expand...

No need to hammer through the lens. They're usually glued, sometimes with a lot of glue but you can heat it up with a lighter and then unscrew the lens barrel until it comes out. If it's a long lens barrel, as one of my 301's has, it'll need multiple heatings because the glue will harden and lock up the threads every time it cools. I didn't have any issues with melting the lens, but it's something to watch out for. Thankfully, newer units are using a lot less glue.

Mine looks like a single piece, but I'll definitively not try to take it apart.

Lens barrel comes off easy, but the module (with the LD) don't! I need break the glue and force the module down using a hammer.

Mine looks like a single piece, but I'll definitively not try to take it apart.

Click to expand...

It can't be a single piece. How did the focus barrel (part #2) get in there? The focus adjuster rides in threads on the inside of the front end casing. It won't fit through the front end's forward opening, and it won't fit through the module hold and/or heatsink socket either. The front end has to be a separate piece.

Look carefully at those grooves on the front end. The edges of the grooves are all bevelled, except for the one indicated in the photo below. If you look closely, that edge is sharp. See the photo below where I have marked it with red arrows. That's where the front end screws onto the host.

As far as taking it apart, if there's nothing wrong with the lens and the focus is good, don't bother. "If it ain't broke, don't fix it." On the other hand, there is no harm in trying to unscrew it by hand. If there is little or no glue, you can usually break it loose without tools. If that happens, you just tighten it back down and it's fine.

eta: d'oh, OF COURSE there is something wrong with the lens, you bloody hammered it out

Take the thing apart, there's nothing left in it to break, you'll learn more about how your laser fits together, and being able to take that off will make fixing it a lot easier.

But if you can't unscrew it by hand and it becomes painful to try, then it's definitely glued and if nothing is wrong with the optics, best to just leave it be. If you ever do need to service the optics, you just heat it up until the glue melts, and then use channel locks or a large pair of pliers to rotate it off. As long as you grip the tool tightly and don't let it slide, then the tool marks will be small. You can pad the tool jaws with electrical tape to further avoid tool marks.

The green arrow points out another hidden feature. The front end of the focus knob can be removed by heating up the glue holding it on. It's a simple piece of cut sheet metal covering some kind of accessory socket. Look at the front aperture and you can tell. Is the aperture a constant diameter for its whole length (~5mm if so), or does it look like a thin piece of metal covering a hollow space? If the latter, then the front end of the knob is a separate piece. Removing it gives much easier access to the lens barrel and allows adjustments to the lens without needing to remove the focus knob.

I should mention I have a 405nm in that exact host. It has the same bevelled edges on the grooves, and the knurling is also identical. The front end is the "short" front end, same as my laser. (On greens and true 303 diode lasers, it is longer.) The focus barrel (part 2, which carries the lens barrel) is likewise short. The power button on mine is identical (curved on top) and there is no separate heatsink. Your laser appears to have all of these features which makes it a Laser 301. In the past lasers in this host were always labelled as Laser 301, SD-301, V301, or similar, but always with 301. It appears that manufacturers are no longer following this convention, as yours is mislabelled 303, and the 303 I just bought is mislabelled 301!

Wrecking the lens barrel wasn't a good idea if you ever want to put this thing back together. It's an M9.5x0.5 thread, so neither M9's (AixiZ lens barrels) nor M10's (from green 301's... green 301's use M10 lens holders, whereas green 303's use M8) will fit it. You can probably have a member make you a replacement though. It takes a 6mm lens; by cutting the lens out of an AixiZ lens barrel and filing the edges a little, it can be made to fit and will work just fine.

Lens barrel comes off easy, but the module (with the LD) don't! I need break the glue and force the module down using a hammer.

Click to expand...

That is actually the focusing knob (1) that you have removed. The part it was removed from is the focusing barrel (2), which is inside of (3). The threads inside (2) hold the lens barrel. I need to make a new parts photo; I took that one when my knowledge of these lasers was much less. Note that the 301 in the picture is a green DPSS, but it's very similar to 301 diode units such as yours. The only differences are that yours uses an M9.5 lens carrier and has a shorter front end.

It might have been better to press the laser module out using a vise. They're definitely solidly in there, usually glued. Even if the laser is dead, hammering can damage the host if you miss or hit too hard. I would only use a hammer and punch would be to knock glued-in heatsinks out of 303's, because I don't see any way to do it. 303 modules are threaded on the front (M11x0.5) but the threads are too fine to be useful in pulling the heatsink if it has been glued.

Here is the photo, which I just modified from yours. Red arrows mark the front end attachment joint and green is where the front cover should be, if present. Any other questions please let me know and I'll do my best!