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Thread: Coherent Sapphire power output problems...

  1. #1
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    Question Coherent Sapphire power output problems...

    I recently got a couple used Coherent Sapphire 488-20 lasers, one works great, the 2nd unit has some really strange behavior, initially it will power up and output
    full 20mw of power, but after about 30sec to a minute it will just shut down, and restart but will only output about 3mw of power. I pretty much assume the pump diode
    is on it's last legs but was wondering how much more juice I could squeeze out of this unit, it appears still capable of 20mw output verified with a lasercheck question
    is how to disable or override whatever safety mechanism is causing the laser to shut down, wondering if anyone has any experience hacking these lasers and controllers?

    I did do some research and the closest thing I found that was helpful is this page. (http://redlum.xohp.pagesperso-orange.../Sapphire.html)
    I attempted to increase the headroom for the diode current hoping it would help, I tried 0.2ohm and 0.5ohm resistor in parallel with the sense resistor, but it didn't
    appear to change anything, same problems.

    I also have serial control over the laser, here is a log of basic startup and operation behavior.

    Code:
    Sapphire:0-> ?lt
    Sapphire 20mW
    Sapphire:0-> ?wave
    488
    Sapphire:0-> ?sv
    6.710
    Sapphire:0-> ?hh
      3591:52
    Sapphire:0-> ?maxlp
    22.000
    Sapphire:0-> ?minlp
    0.500
    Sapphire:0-> ?nomp
    20
    
    Sapphire:0-> L=1
    Sapphire:0-> ?p
    19.990
    Sapphire:0-> ?c
    1.748
    
    <-----------     laser shuts off (about 30sec of full power output)
    
    Sapphire:0-> ?ff
    0
    Sapphire:0-> ?FL
    Fault(s):
            None
    
    <----------- turn main power off/on
    		
    Sapphire:*-> ?p
    0.814
    Sapphire:*-> ?sp
    20.000
    Sapphire:*-> ?c
    0.008
    Sapphire:*-> ?c
    1.703
    Sapphire:0-> ?p
    20.000
    Sapphire:0-> ?c
    1.710
    Sapphire:0-> ?c
    1.709
    Sapphire:0-> ?c
    1.710
    Sapphire:0-> l=0
    Sapphire:0-> ?dt
    19.997
    Sapphire:0-> ?bt
    22.041
    Sapphire:0-> ?c
    0.009
    Sapphire:0-> ?bt
    23.185
    Sapphire:0-> l=1
    Sapphire:0-> ?c
    1.738
    
    <--------------- 5sec full output then shuts off
    
    Sapphire:0-> ?c
    0.008
    Sapphire:0-> l=1
    Sapphire:0-> ?p
    20.000
    
    <--------------- 3sec full output then shuts off
    
    Sapphire:0-> l=1
    Sapphire:0-> ?c
    1.800
    Sapphire:0-> ?p
    1.990
    Sapphire:0-> ?p
    2.157
    Sapphire:0-> ?p
    2.324
    Sapphire:0-> ?ff
    0
    Sapphire:0-> ?FL
    Fault(s):
            None
    
    <-------------- laser stays on now, but with only 2.3mw output power
    I will continue to probably mess with the system untill I kill it, might learn a thing or 2 about these lasers in the process, I'll post my findings along the way if I make
    any progress... any input or suggestions is appreciated! thanks in advance...

  2. #2
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    Default

    PM Phil Bergeron, aka 142Laser. He may be able to help you
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  3. #3
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    Thanks Jem for the info, I will send him a PM.....

  4. #4
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    here are some more results for those interested, I did make progress by modifying the current sense resistor.

    default resistor is 0.015 ohm, I added 1x 0.05ohm as well as 2x 0.05 ohm and 3x 0.05 ohm in parallel to offset the sensed current.

    0.015 ohm = 2.7mw max output
    0.015 ohm + 1x 0.05 ohm = 0.0115 ohm = 6mw max output <--- now we're getting somewhere
    0.015 ohm + 2x 0.05 ohm = 0.0093 ohm = 15mw max output <--- that's more like it, that's pushing it a bit about 20-25% more current?
    0.015 ohm + 3x 0.05 ohm = 0.0078 ohm = eratic behavior >15mw turns beam off but controller thinks it's still on, (thought it killed it... luckily powcycled and all still works)

    right now I'm pretty happy going from 2.7mw to 15mw, but since this is a experimental throw away unit, still curious on other options since I have seen it output >20mw for
    about 30-40 sec before.. so must still be some other things to explore..

    the power up sequence is a bit strange with the modified current resistor, system powers up to set power, but displays really low current draw, after about a minute it
    shuts down, takes about 3 restarts of the beam each time will turn off after a few sec but each time it seems to try adjusting itself until after the 3rd or 4th start it
    reaches set power then shows a much higher current draw but now is completely stable.

    here's another log with the 2x0.05ohm resistors in place.

    Code:
    Sapphire:*-> ?sp
    10.000
    Sapphire:*-> ?c
    0.009
    Sapphire:*-> ?f
    0
    Sapphire:*-> ?fl
    Fault(s):
            None
    Sapphire:*-> ?p
    10.000
    Sapphire:0-> ?c
    0.975
    Sapphire:0-> ?c
    0.977
    Sapphire:0-> ?p
    10.000
    
    <------ 45sec laser shuts off
    
    Sapphire:0-> ?c
    0.984
    Sapphire:0-> ?c
    0.009
    Sapphire:0-> l=1
    
    <------ 5 sec laser shuts off
    
    Sapphire:0-> ?c
    0.985
    Sapphire:0-> l=1    
    Sapphire:0-> l=1
    Sapphire:0-> l=1
    
    ^^^^^ --- laser shuts off instantly but does a strange power ramp during power up
              finally after 3rd try it stabilizes and now shows larger current draw.
    		  from here on laser power is stable.. 
    		  
    Sapphire:0-> ?c
    1.627
    Sapphire:0-> ?p
    10.010
    Sapphire:0-> ?p
    10.010
    Sapphire:0-> ?c
    1.565
    Sapphire:0-> p=13
    Sapphire:0-> ?bt
    23.757
    Sapphire:0-> ?p
    13.127
    Sapphire:0-> ?c
    1.731
    Sapphire:0-> ?p
    13.000
    Sapphire:0-> ?c
    1.723
    Sapphire:0-> ?c
    1.723
    Sapphire:0-> ?c
    1.604
    Sapphire:0-> ?p
    13.000
    Sapphire:0-> p=14
    Sapphire:0-> ?c
    1.661
    Sapphire:0-> ?p
    14.000
    Sapphire:0-> p=15
    Sapphire:0-> ?c
    1.739
    Sapphire:0-> ?p
    15.000
    Sapphire:0-> ?p
    15.000
    Sapphire:0-> ?p
    15.000
    Sapphire:0-> ?p
    15.000
    Sapphire:0-> l=0

  5. #5
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    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    things to explore..

    the power up sequence is a bit strange with the modified current resistor, system powers up to set power, but displays really low current draw, after about a minute it
    shuts down, takes about 3 restarts of the beam each time will turn off after a few sec but each time it seems to try adjusting itself until after the 3rd or 4th start it
    reaches set power then shows a much higher current draw but now is completely stable.

    Sounds like a temperature issue, diode cooler or crystal heater.

    Steve

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