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# Have sweet looking laser, desire to fire. How to figure out what voltage to apply without destroying it by mistake? Answered

Anybody know what sort of laser is found inside a commercial laser copier/printer? I have a fairly chunky LD (housed in heavy brass shell w/ 3 leads coming out of the base) that I'm pretty sure came from a Konica-Minolta commercial laser copier. I know they can be pretty delicate so I really want to avoid experimenting with random voltages, and so I'm looking for any approach that isn't "shoot first and ask questions later. Can the forward voltage be determined safely? Any thoughts on this are appreciated; I've only just begun to understand LEDs at all...
The numbers printed on the circuit board were not helping me except to figure who may have made the machine it's from, but in case they tell you more, here they are:

PU639T102 -01
SEC-55194V -0

THANKS!

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## Discussions

Hi i just et the same it not too good its infrared= invisible and not too high needs 75ma and 2.2v itsno problem i u put 2v the source is negative the middle pin and teh positive is where are 3 resistors it has 5 mw u can find it here http://www.datasheetarchive.com/LT026MD-datasheet.html this diode is what contains. Have fun and dont watch in it its ibnvisible and destroys ur eyes!!!

No idea on the part numbers, but it's the current you want to consider, not the voltage. Build yourself a constant current circuit such as THIS and use a resistor of 47R to give you around 30mA. Once you've found the right connections and get a light, reduce the resistor value until things start getting warm.

Thank you for your reply -- very informative! That gives me a great jumping-off point.
I am assuming that your capitalized "THIS" was a hyperlink, but unfortunately it did not appear as one to me. I am very interested in what you referred to, but I'm sure I I can find an instructable for building a constant current circuit ;-) Of course, I dd just get a benchtop power supply with a constant-current feature for Christmas, so it looks like I've got my first use for it.... unless you're aware of some reason that would not be the best way to go about it. You seem to know a lot more about this stuff than I do!
Thanks again for your reply and advice :-)

Sorry about that - THIS is the sort of thing I was referring to.
Your constant current bench PSU will be OK as long as you can accurately set it that low.  It's very easy to blow laser diodes up with over-current.

Just thinking more about this, I was thinking 'photocopier - bright green laser', but I don't know if they all are (or at all nowadays).  If it's an infra-red laser you won't see the beam and could possibly damage your eyes.
I'd tape over the end and apply the current source, using a multimeter to check for 1V to 2.5V across the pins which would probably indicate you've got the right ones the right way around.
If you've got light, great.  If not, look at it through a video camera which should show if it's lit or not (I've never tried this, but heard it works).