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I am scared

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Tallaxo

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OK I managed to fry my driver board of my 35mw cni, that I turned into my variable power greenie for my scanner.

So I hooked up the pump diode direct to my variable PSU . OK it still lases ok, but now it likes to sit at 1.6v 400ma before it starts to lase. is this normal for an unregulated green, it will quite happily suck up 700ma before it gets a good power at the same voltage. It does not get hot at this level and will not demand anything more than 1.7v.

Duty cycle seems to be still 100% as I have had it on all night, but 700ma? is that normal?

Jase
 





Hemlock_Mike

Hemlock_Mike

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Jase ---

I sat back and read your post several times.  The readings are most unusual.

The 808 LD's typically have higher Vj than 1.7 volts.  This is almost like half of the driver is shorted (if this is possible).  Running the other half at 700 mA will probably shorten the life of what's left there trying to make up for the other part.  Current is typically the critical paramiter for lasing threshold and this current is provided by the voltage. Something is outta whack here.
This is a wild ass guess on my part but it appears something bad has occurred in the LD.

Mike
 
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Tallaxo

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Thanks Mike, I guessed it was kinda weird.

I am pretty sure it is on its way out, my psu is current limited to 700 ma at the moment, so i guess i will just run at that until it dies on me. I have to say though, the whole module seems pretty robust and has taken a lot of punishment . I have been running it all night at 600ma with 100% duty cycle, yet it refuses to die.

However power input remains the same for full power 600ma @1.7v = 1.02w and 2.3v@450ma = 1.1w. so power input to achieve beam is relativly equal, its just pulling a lot more current at a lower voltage.

I guess time will tell.

Jase
 
Hemlock_Mike

Hemlock_Mike

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Jase --

Those readings still don't make sense to me. You better be looking for a new 808 LD !!! I still don't understand the "cool" operation of the module except that the "math" for the power is almost the same.
Throw 12,000 volts at it and smoke your coffee table like I did !!!

Mike
 
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Tallaxo

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Mike, it finally died on me :'( the green output got fainter and fainter , however all is not lost, as the pump diode is still working. I guess I just cooked the MCA . the pump is still visible behind the IR filter (i can see a pinprick of red light that varies in power , with the psu) so I guess all that is left to do, is rip it apart and make an IR burner.

I never liked green anyway :'(

Jase
 
Hemlock_Mike

Hemlock_Mike

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Jase --

Don't blame the MCA yet. The LD will output a faint red "beam" but it has become an LED - not an LD. That red light you see may not be laser and not pumping the MCA. There's a bunch of us here who done that :'(
The diode is usually the first to go. Got an 808 ???

Mike
 
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Tallaxo

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Pretty sure the pump is ok Mike, I could always detect that little pinprick of red, when it was working well, just before lase threshold. I can sometimes still get a little flicker of green now and then, though very faint.
Guess it is time to start looking for a greenie.

Jase
 
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SenKat

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I happen to know a certain raffle going on for a greenie ! LOL !!!
 
L

Lazergirl

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:eek: ewwwww .....a greenie is something entirely different where I come from! lol ;D x
 
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SenKat

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Lazergirl said:
:eek: ewwwww .....a greenie is something entirely different where I come from! lol  ;D x
Click to expand...


HAHAHAHAHA !!! NOT that type, silly rabbit !
 
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pseudonomen137

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Tallaxo said:
Pretty sure the pump is ok Mike, I could always detect that little pinprick of red, when it was working well, just before lase threshold.  I can sometimes still get a little flicker of green now and then, though very faint.
Guess it is time to start looking for a greenie.

Jase
Click to expand...

Well, to reitorate what Hemlock Mike is saying, that doesn't mean you still have a laser on your hands. I've had many diodes die on me where they don't exactly die. When overdriven, the end facets in the cavity can get damaged, which severly affects gain in the cavity. As such, the diode may still work either as an LED or laser, but the output can be diminished to a small fraction of original output (I once brought a 200mW Aries down to <20mW this way). Its possible its still faintly working, but not powerful enough to reach the threshold for the crystals.

It is, of course, possible to have damaged the crystals, but I would think the damage threshold there would be far higher than on the diode. (of course, its all total guesswork, but I'd still be blaming either the diode or alignment for your loss of green - not the MCA)
 
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Tallaxo

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Ahh well, I finally destroyed it by trying to get to the MCA :( the pump diode fell apart and I cracked the Crystal assembly, oh well, live and learn I guess.

Better start saving for a new laser.

Jase
 
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