short die open can dies at 250mA. alas

[phenol]

with a total run time of 4-5 hours, of which 80% at meager 150mA and the rest 19.99% at 200mA, today, 18th of March 2008, after experiencing the "safe" current of 300mA for 5 seconds and happily lasing at the "longevity guaranteed" current of 250mA for another 5 long seconds, died my first ever burner laser diode extracted from a 20x lite-on drive, aka short-die open can. it sure stood up for its name
its case temp was about 40-42C; it was lasing when it abruptly dropped in power, all connections were secure, so it wasnt an intermittant lethal spike that sent it down to dim red 660nm LED hell.
the bottom line is that its optical power handling capabilities seem to be somewhat inferior to its long-die relatives.
below is a close-up /500x/ of its upper bar side close to the rear base /rear.jpg/. take note of the ragged edges and the darker bands caused by too much heat/optical power :. the front facet looked alright.
+rip+

 

[chido]

Damn, sorry to hear that, I sent a short open can to Dr. Lava for testing, so we'll see how it compares to yours.

 

[Switch]

Was your drive under warranty? Maybe you can take it back and say "Hey! The diode from this drive , which I carefully extracted, with no mercy for the other components, died before it was supposed to while I was overdriving it and I'm frickin mad I demand you give me another one!! :"
(just a little joke, don't get mad :-X)

Maybe you just got unlucky and had a bad one, or maybe your multimeter isn't working right? :-/

 

[phenol]

the MM is a 6 1/2 digit Fluke, so i kind of trust it. regarding the warranty remark, there's no way to extract this from the liteon without leaving visible telltale marks. LG's, on the other hand, are perfect in this rgard. all u need to do is remove the back cover and snap the LD off the pickup, leaving jo marks whatsoever.
anyway, i have two long-die open cans yet to murder.

 

[Switch]

Well, that's good.Better luck with those!!

 

[drlava]

Chido sent a short open can for testing, and here are some results. It could not achieve the same output as the long die open can, it hit the knee at about 350mA and 200mW. The plastic lens had the rear aperture opened to allow for higher power.

 

[Hemlock_Mike]

Lava --

So poetically stated ;D We mourn its demise. Now in middle English please !

Mike

 

[drlava]

More simply, The short die open can doesn't appear to be able to achieve the powers that the long die open can diode can safely.

Here is a comparison plot. As you can see, the short die diode has a lower lasing threshold, but at about 350mA the curve turns near flat. I didn't push this one beyond that so that it could be returned to chido in working condition. The long die, on the other hand, doesn't begin flattening till about 480mA. It also maintains a higher gain through the test.

 

[adgmeijin]

Hey Phenol i have the same experience as yours, i have killed my first ever LG20x DVD laser burner handheld yesterday, cuz i try to push it to 420ma but im accidentally i snap my hand to make a dangerous 450 to 500ma into it..then it dies ... :'( now im trying to buy another LG20x, next payday... :-[

 

[chido]

Thanks for testing the diode DL. (and thanks for not murdering it) ;D

Adgmeijin, yours was a long open can diode, not a short open can.

 

[adgmeijin]

Chido, why does this happen? i check my driver it was ok, i have 3 ohm resistor but my DMM reads it as 3.3ohm, i replace the 100ohm trimpot so 3 ohm resistor was all alone there, when i test it it was actual doin fine but after some resoldering adjustments, it test then it puts out a high beam of red then gone, after that , i test the driver it was putting out 450 going 500ma according to my DMM, so hows this? :-/ :-[

 

[chido]

If you only had a resistor in there with no pot, then the only thing I can think of right now is that you didn't wire up the driver correctly and all the current from the batteries went straight to the LD or that your DMM is broken and it didn't give you the exact measurement of the resistor, so maybe you were using a different resistor. Can you tell me what the color bands on your resistor are?

EDIT: Or you might have connected the LD back to the driver without discharging the capacitor. (although that doesn't explain the 500mA of current) :-?

 

[adgmeijin]

on my resistor band color it was orange, black, gold, gold it was 1/2W resistor type. my driver was working good, i think i ground somthing inside my host, thats why after my red laser died i decided to change every thing into neat one then buy another LG 20X DVD Lightscribe.

 

[phenol]

your resistor is 3 ohms, 5%. when you measure its resistance with a dmm, first short the probes, note the readout /probes wire resistance, depending on dmm calibration/, connect them to your resistor and subtract the probes resistance from the value shown on the display. Ideally, such low resistances are best measured using the 4-wire method.
i am truly sorry yours died so quickly, however I am still reluctant to think that those diodes will last long /more than an incandescent lightbulb/ at such levels just because they can have an almost linear response up to 480mA.
I made a SMPS portable device running at 300mA and also a custom-made massive brass housing into which i will put another one running at 350mA. Will see how long before both pop.

 

[adgmeijin]

its was actualy an accident, its my fault of changing and replacing resistor without testing the driver mA first, the LD was connected when im doing that, what do you think was wrong here, im soldering in the driver while LD was connected, then following battery connection without knowing the mA... :-/ :-[

 

[phenol]

:-/ many things could have gone wrong. doublecheck the solder joints and component orientation. Also, solder the cap on the new LD taking care of its polarity. if you still have your dead LD laying around and it emits some faint red light, you can use it as a dummy load /pressed in its module for heatsinking/ ... furthermore, always disconnect power from circuits before soldering and make certain the tip of your iron does not accumulate static charge...blabla... measure twice, kill once.