For those of you with a changchun pointer - mod

DaFiend

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Sep 23, 2004
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i came across this mod for the changchun pointer if anyone is interested /ubbthreads/images/graemlins/smile.gif
 
DaFiend- thanks for this, I have been looking for it. I have an old Changchun that always had a pretty crappy output. I never could get it open. The 'acetone on the gold ring' part of the instructions is what I needed. Looking forward to trying this
Thanks again
 
Keep us informed on how it goes photonic /ubbthreads/images/graemlins/smile.gif
 
OK I tried this out last night. I was able to use the acetone to loosen up the threads. If you look at the mod it says to turn the front of the laser pointer tube 'as if to tighten' meaning, use the front part to loosen up the laser diode and driver board. I was unable to get that to happen. I'm suprised because this pointer is quite old, from 1999 or thereabouts. I would think that if modifications were a problem, they'd start gluing them together later (closer to 2002 when the prices dropped).
The acetone did loosen the threads to where I was able to get the front half of the pointer body OFF (by unscrewing CCW) but turning CW did not budge the diode/driver ONE BIT. With the front off, I injected more acetone around the driver, and I even put some in through the open button hole (removed the silicone rubber button cap) to get it from both sides. It looks like the diode of the pointer shown on the web page was not glued into the tube, or was glued very lightly. Mine would not budge. I put the front tube back on loosely and tried to use it like a handle to pull the diode/driver out but it did not move. I put over 100 lbs of pressure on it to get it to move. I was at the point where I thought the body of the pointer would buckle so I quit.
I left the acetone in the joint around the tube and the diode/driver board so maybe today it will have loosened up the adhesive enough. I will try again. If it never comes loose, you can use the exploded view on that page to guess where the pot is and just cut a hole in the tube at that point. That's plan B. I just hope the acetone or it's fumes don't cause any damage to the optics. I shook out the excess liquid but hopefully there's enough around the diode heatsink to work.

PS Does anyone know what that white putty like material is they use to keep the IR filter on?
 
Er well OK that didn't go so well. The pump diode assembly never came loose. So I used the pictures on the site to approximate where the trim potentiometer was, and cut a hole in the pointer where it should be. It was not exactly there, on mine it was a little up and to the right of where it is in the picture (to the left of the transistor in the pic). The laser drew about 280mA from fresh AAAs stock. Turning the pot 90 degrees CCW resulted in no output and a ~40-50mA draw. I backed it down and it started to lase again but it wouldn't give me any significant power gain.

Again this laser is quite old, I think from 1999 or 2000

I watched the current and put my finger over the output, and the current dropped significantly which leads me to think this unit is monitored by an output sensor.

Anyway the best I could get out of it was about 320mA of draw and a brighter spot, but not so much that it was worth messing with. The spot got bigger and slightly 'blobbier' but this may have been my imagination (can boosting the power make it lase in a different TEM mode??)
It was strange, but when turning the pot CW it would go around at least twice yet the beam stayed the same and the current stayed at about the original 280mA

Questions:
-Does anyone else have a Changchun and can you corroborate what I found?
-Do DMM readings of current mean anything? The output is pulsed and there's no large storage cap so I would assume the input current is pulsed as well so the reading you get depends on the count frequency of your DMM and how it integrates current readings...
 
Without the extra resistance of my DMM leads and alligator clip wire jumpers the spot is now about as bright as my other no name green pointer. I suspect that one was always >5mW. I got a very early sample before they got FDA approval so I think I've been spoiled all this time as to how bright I thought 5mW was.
Anyway this changchun is hacked up pretty badly so it may be a candidate for future more extreme mods.

PS I have some IR laser diodes from laser printers. I'm wondering What frequency range you have to supply the KTP crystals to get them to convert IR to green output?
 
808nm is the standard IR wavelength for the green laser diode.
808nm IR--->NdYV04 crystal [changes frequency to 1064nm]
1064nm IR--->KTP crystal [doubles frequency to 532nm]
532nm = Green
 
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