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Thread: Picked up 2 coherent 900 series!

  1. #1
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    Default Picked up 2 coherent 900 series!

    Hi there!!

    Last weekend I picked up two coherent 900 series krypton-ion lasers from a a club, which upgraded to DPSS a couple of years ago.
    The system has been converted by Laserimage in 2001 for show use, adding PCAOM's and refilled with Krypton.. from what I read off the stickers i believe the system initially was built using argon.. is this correct?

    It has been used from 2001 to 2008 on a weekly basis, only 3 hours per weekend. It has had regulary maintanence in this period. During the last maintenance in 2008 the power has been measured at 5.9W and 6.1W all lines.

    In 2008 the venue upgraded the lasers to DPSS. The PCAOM's and fiber launchers were removed.. but the lasers remained untouched.. until now

    Here are some pictures:
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    The beasts in the van

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    overview

    Details of system #1.

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    PSU opened overview
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    close ups of the PSU


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    The outside with some controls and labels

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    Details of the tube. Looks like an Coherent I-90


    System #2:

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    closeups of the tube

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    And the label of the second tube.. even older than I am

    There are also 2 3-phase transformers so the machines can be fed from european outlets.

    I can't wait to fire them up. There is a step-by-step instruction sheet included, which tells me to start the system up, wait 2 minutes, slowly turn the beam to 40 VOLT/AMPERE, wait for another 2 minutes.. etc.
    don't have the sheet right here but I'll post the exact instructions here later..
    As there is no running water in the workshop I'll find myself a pump and bring a huge amount of water, and build a closed cooling circuit. Is there a minimal water pressure level I should respect?

    Now As the system hasn't been touched in 4 years.. what steps should I take before even thinking about powering it up?
    I read the tube pressure should be sufficient, or else the PSU might blow.. where can I check this?

    I'm afraid something like this will happen: http://www.youtube.com/watch?v=V4gOg-TESKk

    I know there are some of you very experienced with this equipment.. I'd very much apreciate your input!

    Thanks!
    Last edited by SideFX; 07-24-2012 at 04:35.

  2. #2
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    Startup procedure:
    1. Plug in the 3-phase power plugs
    2. turn on water / switch on pump
    3. Plug in the (PCAOM) driver power plugs
    4. On the remote: switch key to right
    5. Check that the Laserbeam-knob is turned all the way down
    6. Press start
    7. Wait for 2 minutes
    8. Switch on the 'Autostart' switch until the Volt/Ampere meter is at 40, then immediately switch off the 'Autostart´
    9. Wait for 2 minutes
    10. Turn up the laserbeam-knob _slowly_ till 50 on the Volt/Ampere meter.
    11. Wait for 2 minutes
    12. Turn it up to 60

    Shutting down procedure
    1. Turn the laserbeam-knob all the way down
    2. Turn the key on the remote left
    3. Let it cool down for 5 minutes
    4. Shut down water
    5. Unplug all power plugs

  3. #3
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    Throttle the flow with a valve, and make sure you can prime the pump when you do.

    The constrictions inside the laser will not handle 50 litres a minute, and the plastic flow switch rotor would distort/crack at that point.

    I'll try and get some notes together for you, plus the tap charts.

    Steve
    Last edited by mixedgas; 07-25-2012 at 10:41.

  4. #4
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    Hi Steve!

    Thank you for your thorough analysis.. I was hoping someone with your experience was willing to guide me through

    Quote Originally Posted by mixedgas View Post
    Ok, yes, they can regassed easily enough if you have the 25,000$ worth of equipment to do so. I do. I love 900s, I made a lot of money using and working on them. Makes a good pure krypton or a whitelight if you change the gas out. Odds are they changed both the tube fill and the magnet for red. 900Ks from the factory had special magnets wired in series with the tube. Normal Argons have a 160 Ohm magnet in parallel with the tube DC supply.


    WARNING
    . THE TINY WHITE AND GREEN AMPMETER ON THE SIDE OF A 900, unless MODIFIED, does NOT read the ACTUAL AMPS to the TUBE. UNLESS MODIFIED (1 Resistor needs changed) they read a factor of two HIGHER then the actual tube current. IF some one messed with the calibration, one of your first steps is to check it.

    60 is actually a setting of 30 ACTUAL amps, this is about max current for the tube for CW service. 35 ACTUAL AMPS is maximum for tests, and 25 ACTUAL AMPS is a good number for long term use.
    I presume it isn't modified then as the startup instructions state to crank it up to a reading of 60 eventually.. which wil correspond to the maximum tube current of 30A.



    The tube when in the Opthalmic use ran at low idle and was popped up to higher powers for a few seconds.

    I will get back to you with desired tube voltages and reference current. I need to look at my notes at home.

    WARNING, you WILL need to set the taps on the internal BUCK/BOOST transformer to NOT exceed 40-60 Volts of REG VOLTAGE on the passbank when the current is turned down. You may need to set the cathode transformer taps as well. I have the TAP CHARTS, too.

    Do you have the external Euro transformers to get the 380/410 down to the US 208-220V ?
    Yes, I have them too.
    I have the system as it was when it was last turned on in 2008. Since then it hasn't been touched except that the PCAOM (which was in an external box) and the fiber launchers where removed.




    Do not exceed 60 PSI, expect to need at least two gallons per minute of flow. There is a analog flowmeter hooked to a relay.
    55 gallons of water in a tank without external cooling is 40 minutes of operation at full power for these, before the overtemp trip sets in.
    I have a pump which will do about 10 PSI, and 50l (about 13 gallons) a minute.. so i should be in the safe zone I presume.
    For testing I will bring 100l (27 gallons) of water.. i hope this will suffice for a couple of minutes testing.


    Quote Originally Posted by mixedgas View Post
    I have the schematics if you need them, but they are rather expensive to scan/copy.

    DO NOT ENABLE THE FILL/REFILL SWITCHES ON THE HEAD UNLESS THE TUBE VOLTAGE IS MEASURED AND FOUND TO BE OUT OF SPEC.

    Its a stretched I90, aka I90MRA or I90MK. They have tubes about 2 inches (5 cm) longer then a I90, and a special light weight magnet.




    If I were you, I'd like to know the modification(s) to the PSU to remove the foot pedal and medical safety board, or if they just turned on the "SERVICE" switch. This matters in it affects how the PSU will protect itself in emergencies.
    Where is this switch located? I was under the impression the 'Service Switch' knob on the side of the 900 is merely an indicator, not a switch, as i wasn't able to move it.
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    Once you have a working PSU, we can go on to the tube pressure tests. This is done by measuring the tube voltage at a specified current.

    It is best that you unplug the fill wires now. These are the wires to the two fill solenoids mounted on the tube assembly. Label them and disconnect them, and tape them off so they do not short anything. It is important to know which is the "ready" solenoid and which is the "fill" solenoid.
    I thought I only saw one solenoid on the tube assembly:
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    Or is this not a fill solenoid? I will check this more thoroughly later..

    I question the power levels you state.

    If they did 5.1 watts, they are either Argon or Mixed Gas fills. If mixed gas, and doing 6 watts, they were being OVERDRIVEN. A pure Krypton I90MK does about 1.7 to two watts of red.

    A I90MRA Argon will easily do 7 watts all lines multimode Argon when brand new.

    My I90MRA when Whitelighted does about 4.2 watts all lines.
    I guess I was in error when stating is was refilled with only Krypton. It has run as a whitelight laser so it should be an Ar/Kr mixture then. I will scan and post the notes on which the measurements have been written when I'm in the shop later this week.


    So is that the Coherent medical service tag, or the tag installed after they were repumped?
    Í can only guess it is the medical service tag. Based on the notes and what the previous owner told me I believe it was repumped in 2001.

    Your beams will be fat. Expect that... The resonators will be easily mis-aligned in transport. Expect that...

    900s are some of the best ion lasers ever made, Expect that....

    Steve
    Thanks again for you thoughts.. I'm very excited to get this thing started
    I will get some additional info soon.

    Best,
    - Jeroen

  5. #5
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    Throttle the water flow with a valve, and make sure you can prime the pump when you do.

    The constrictions inside the laser will not handle 50 litres a minute, and the plastic flow switch rotor would distort/crack at that point.

    I'll try and get some notes together for you, plus the tap charts.

    The coil you mention in the picture is the blocking coil for the ignitor, it keeps the HV pulse out of the PSU passbank, while passing the full DC tube current.

    The little green toggle switch to the right of the coil in the picture is the fill switch. Its center position is off. You toggle it one way to prime the gas fill, turn it off for a few seconds, and then turn it to "fill", and it will then dump a small amount of gas in the tube. This means you most likely (I'm 99.95% sure) DO NOT HAVE autofill installed. It can take 10-20 minutes some times to see the effect of toggling the switch, and too much toggling, or mis-wiring the coils, will instantly overfill the tube.

    The fill solenoids are on the top of the magnet on the stainless steel gas plumbing. The SS tubing is very fragile, do not attempt to bend it for any reason. Bending the tubing to any major degree can cause the thin weld at the cathode end bell to snap, letting the tube up to air.

    Have you tried "pulling" on the service mode light? Most of them are pull switches. If not, its a toggle switch just under the wooden lid. There are two versions.

    Make sure you learn how to slightly twist and pull up on the cover and side panel interlock switches to defeat them.

    If the water used to cool the lasers was corrosive or dirty, buy a bottle of CLR, dilute it 20 to 1, and flush it through the laser a few minutes with your pump.
    I'm sure there is a equally mild and harmless Euro clone of CLR some place, website is here:

    http://www.jelmar.com/faqselect.htm

    Everything that touches the water is plastic, silver plated, brass, rubber, or ceramic, so a few minutes of CLR will not hurt this laser.
    It can make a dramatic difference in lifetime and power if the cooling passages around the tube contain mineral deposits.
    CLR cleans that out in minutes, forming sludge in your cooling tank.

    Do not use De-Ionized water to cool this laser, it will corrode it. (laboratory user detail)
    De-oxygenated water is fine, however (Chiller owner detail)

    Usually the spare mains fuses are laying in the bottom of the power supply tray, you might want to see where they are. They flop around during shipping and can cause damage. The big Fuses are about 80$ each new. I have a surplus of them for a few dollars each, if you need them. I've seen about 12 of these units with the floating spare fuses where the plastic bag has broken, so please check.


    While you are not in the lawsuit happy United States and thus still have "Free Will", please be very careful when the covers are off.


    You can have 14 kilowatts of energy flowing through you with this system, if you do not take care.

    Also, the mirror adjustment screws on the ends of the resonator are extremely touchy. If its not lasing at first, take it very easy on the screws. A fraction of a turn covers the entire lasing range. Don't ever touch the pivot screw in the corner of the mount.

    Also make sure the plastic HV covers stay on the Brewster stems, if they are not there, the metal covers can slide into the anode or cathode in some cases and kaboom!

    If you have not worked with a ion laser or arc lamp pumped laser, before, it is advisable to find a experienced person.

    There is much exposed dangerous electricity in that system, and not all of it is clearly labeled.


    22 gallons of tank water is about 15-20 minutes at full power. I do not know if whomever modded the system removed the thermal cutout wiring, so time it to 10 minutes and call it quits. DO NOt touch ungrounded cooling water in a plastic barrel. The magnet water flow is grounded if installed properly. Unlike some older SP products the water is not exposed to the anode, so these are quite safe. (When wired to factory specs)

    PS, the power meters are based on photodiodes and will not read true with the changing whitelight spectrum. They will serve as a good means of tuning the cavity. Don't be shocked if you need to a alignment and cleaning of the optics after years of sitting. Usually they stay well aligned, but you never know after shipping.

    Steve
    Last edited by mixedgas; 07-26-2012 at 07:59.

  6. #6
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    Here is the tap chart for a basic 900 series argon without dual tubes or a dye laser, on 60 Hz US standard Power.

    Remember that a mixed gas or krypton tube will have a lower tube voltage then argon tubes.
    So you might have to tap down a bit.

    The critical thing to watch is the passbank voltage, and it will max out at lower currents if not tapped correctly.
    The passbank voltage raises as the tube current decreases. This is why you start the tube at midrange in the instruction sheet for your modified laser.


    Steve
    Attached Thumbnails Attached Thumbnails 900seriesTapChart.jpg  


  7. #7
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    See the attached notes I found inside the machines. Appearently they are maintenance logs with power readings.
    Can I presume that:
    - B+30 is the Tube voltage at a tube current of 30 Amps? and..
    - P30 is the laser power at 30 Amps tube current?

    laser #1 (1976)
    ----
    20-11-2002
    B+30 = 241V
    P30 = +6W
    PR = .650
    T = KR+

    ----
    04-11-04
    P30 = 4.5W
    B+30 = 241V

    ----
    05-11-2005
    P30 = 4W
    B+30 = 243.3
    Ony brewster windows cleaned

    ----
    08-06-2007
    P30 = 3.5W
    B+30 = 247V
    Everything cleaned


    Laser #2 (1980)

    ----
    10-07-2001
    P30 = 5.9W
    B+30 = 236V
    Tank = Krypton
    PR = 1.1W
    IC = 22.5A

    ----
    26-05-2004
    P30 = 4.2W
    B+30 = 242V
    PR = 1.1W

    ----
    04-11-2004
    B+30 = 245.5V
    P30 = 4.3W

    ----
    03-11-2005
    B+30 = 246V
    P30 = 3.6W
    Only brewster windows cleaned.. was 2.5

    ----
    25-01-2006
    P30 = 3400
    B+30 = 247V

    ----
    08-06-2007
    P30 = 2.8W
    B+30 = 250V

    ----
    20-07-2007
    B+30 = 251V
    P30 = 3.35
    P31 = 3.6
    Attached Thumbnails Attached Thumbnails IMAG0865.jpg  

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  8. #8
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    Yes, 30 is a nice consistent amperage to run and test at.

    245V is about right for Argon for decent lifetime. I keep the pure Argon at 247-250 in academic use.
    Krypton usually runs about 7-10 V lower then Argon in the same size tube.

    Whitelight mix is usually about 5-7 volts lower then pure Argon in the same size tube.

    As long as the correct pressures and cathode currents are maintained, those lasers will live for a very long time.

    Higher pressure is good for whitelight lifetime, but it lowers total power and reduces red power.

    Pred would be the red power out of the total power.

    Steve
    Last edited by mixedgas; 07-27-2012 at 11:41.

  9. #9
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    Steve,

    Quick note regarding the CLR, I also need to clean my Ion, do you think something like

    http://www.crispandbrite.co.uk/dfc-c...946ml_p64.aspx

    Would be suitable ?

    We seem to be unable to buy CLR in the UK (and I assume Europe) in small volumes.. you can buy larger amounts x12 bottles.



    Nigel.

  10. #10
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    That looks like pre-diluted CLR.
    It would be fine.

    Remember, your end goal is a bucket of chips of white crud. If crud is present in the laser. So it may need to circulate longer if pre-diluted.

    You Euro guys really need to get your enviro-weenies under control. Ours are very useful, but yours seem to be overkill.

    Steve

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