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Lines in defocused spot?

CurtisOliver

CurtisOliver

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Nice find Diachi, DTR deals with these diodes very often, so he knows what he's talking about.
 





momo1717

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diachi said:
It doesn't look terrible in the first picture, but certainly worse in the last two. I imagine you had it focused differently between images.

It's possible that the diode is damaged/defective. That doesn't mean it'll die any time soon though. It may work fine for ages - just with lower output/efficiency.

DTR has talked about the issue in the past - as have others:



Full thread: http://laserpointerforums.com/f65/super-inefficient-m140-85310.html#post1234836
Click to expand...

CurtisOliver said:
I'm afraid I might have to agree with Sta. At first glance I thought it was multimode lines, but the laser doesn't sound healthy. Might have to get another m140.
Click to expand...

I did yesterday a few more tests and the diode died more and more. I have no idea what happened, but the output power is now like 5mw or even less. The spot is barely visible with the naked eye. So sad :(
 
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CurtisOliver

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Sorry to hear that Momo1717. :( I had a m140 and it died suddenly as well. Mine went due to a simple back reflection of the lens spring. Diodes can be killed easily.
But on the positive side, you now have an excuse to seek out a new laser ;)
 
momo1717

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CurtisOliver said:
Sorry to hear that Momo1717. :( I had a m140 and it died suddenly as well. Mine went due to a simple back reflection of the lens spring. Diodes can be killed easily.
But on the positive side, you now have an excuse to seek out a new laser ;)
Click to expand...

Would you recommend to buy the same one again? I would like to have a green one, but they are so expensive when over 100mw... :p :)
Yeah, what is the purpose of that spring? ... I just took off the lens and noticed that spring inside.
 
CurtisOliver

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I would recommend you look into a 9mm 445. The purpose of spring seems to be for keeping the focusing ring tight so it doesn't wobble in the thread.
 
momo1717

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CurtisOliver said:
I would recommend you look into a 9mm 445. The purpose of spring seems to be for keeping the focusing ring tight so it doesn't wobble in the thread.
Click to expand...

I'am sorry:yh:, but could you explain me please what the difference between 9mm and the other one is, exept that the second one is 9mm in size and that is with 2.5 and 3.3W more powerful. Is 9mm better?
(The first is the one which is now broken)

1: 2W 445nm M-Type M140 Blue Laser Diode In Copper Module W/Leads | eBay

2: Nichia NDB7875 445nm 9mm Laser Diode In a Copper Module With Leads | eBay

Never mind, just found this: http://laserpointerforums.com/f65/new-9mm-445-diodes-73284.html#post1056982
 
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diachi

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momo1717 said:
I'am sorry:yh:, but could you explain me please what the difference between 9mm and the other one is
Click to expand...

Different package size - the M140 is in a 5.6mm package, the higher power diodes are in a 9mm package. The larger form factor allows for better thermal characteristics (I guess the extra space for a larger die and larger pins for more current helps too) which allows for more powerful diodes.
 
momo1717

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diachi said:
Different package size - the M140 is in a 5.6mm package, the higher power diodes are in a 9mm package. The larger form factor allows for better thermal characteristics (I guess the extra space for a larger die and larger pins for more current helps too) which allows for more powerful diodes.
Click to expand...

Thanks for explaining!! :):yh:
 
bdgreenb

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I just have to chime in. Are you sure its not your batteries or possibly the driver? Low current to the diode can also cause individual lines to wink out. DTR even stated that lack of current can cause this effect.
Its just always good to double check everything before you go for a whole overhaul of a laser. I've had a number of lasers i thought were dead spring back to life as if nothing ever happened by simply double checking every connection and my batteries.
 
diachi

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bdgreenb said:
I just have to chime in. Are you sure its not your batteries or possibly the driver? Low current to the diode can also cause individual lines to wink out. DTR even stated that lack of current can cause this effect.
Its just always good to double check everything before you go for a whole overhaul of a laser. I've had a number of lasers i thought were dead spring back to life as if nothing ever happened by simply double checking every connection and my batteries.
Click to expand...


^^^Fair point - hopefully OP gets lucky and that's all it is.
 
momo1717

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bdgreenb said:
I just have to chime in. Are you sure its not your batteries or possibly the driver? Low current to the diode can also cause individual lines to wink out. DTR even stated that lack of current can cause this effect.
Its just always good to double check everything before you go for a whole overhaul of a laser. I've had a number of lasers i thought were dead spring back to life as if nothing ever happened by simply double checking every connection and my batteries.
Click to expand...

Unfortunately I'am 100% sure, because I tested the module itself also on a DC power supply and it was the same.
When I first got the module and the driver I also noticed that effect when the current was too low, so I can confirm this, but now at the end it was like 100 times more.
 
DTR

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momo1717 said:
Unfortunately I'am 100% sure, because I tested the module itself also on a DC power supply and it was the same.
When I first got the module and the driver I also noticed that effect when the current was too low, so I can confirm this, but now at the end it was like 100 times more.
Click to expand...

When at threshold current you can watch the different lasing lines light up as you go up in current. That would be normal but 600mA-1.8A it should be uniform but yours looks like some of them have gone out altogether. What laser driver did you say you were using?

The NDB7875 is a more robust diode for sure but I would rule out a problem with the laser driver before getting another diode. If there is an issue you want to figure that out before connecting another diode to it.:beer:
 
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