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Thread: Medical Argon Lasers???

  1. #31
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    Quote Originally Posted by perseus View Post
    The output appears much brighter than my 29mW Argon (with Argon glasses on of course) but I have no way to measure the optical power properly yet. In the unlikely event that the relationship between light intensity and photovoltaic potential of a red LED is linear then it is 4.5 times as bright = 130mW.
    Hi Rodger;

    It sounds like you may need to walk your mirrors in. That 909 tube should be making a hell of a lot more than 130 mw! More like 1-2 watts! The spot on the wall should be damn near blinding to look at when you have the PSU turned up.

    My smaller, air-cooled 903 tube is cranking out something north of a watt right now. (Don't have a power meter that goes up high enough to say just how far north of a watt it's actually running.) And this was after a *very* brief adjustment of the mirrors. My guess is that your optical cavity is similarly misaligned.

    Put it this way - my tube is smaller than yours, yet it will melt black plastic. So your 909 tube should be downright dangerous when it's lasing properly. Give the mirrors a tweak and see where you end up. (Only move one adjustment at a time, and go back and fourth 1/3 of a turn or so until you get it peaked. If you don't see a change, then put it back where it was and try the next corner.)
    Label B – two wires – purpose remains unknown. They can be insulated and left unconnected to anything.
    The purpose of these wires is to pull in the relay that controls the blower. Since you don't have the original back panel for your power supply, you don't have this blower or the relay that energizes it. You can simply insulate the wires, or you could use them to power another relay if you wanted to add additional cooling to your head. (That's what I'm going to do with mine anyway.) The relay will pull in as soon as you power up, and will stay on even if you break the interlock.
    Label D – two wires – Adam suggested these might be the tube current monitor but I have not tested them yet. In any case they do not need to be connected to anything.
    I have confirmed that this connector *is* in fact designed for you to be able to measure tube current. It's isolated from the starting pulse too, so you don't need to worry about frying your meter. Unfortunately, I don't know what the conversion factor is from volts to tube current. (Still researching that.) I get readings ranging from .46 volts at idle to 1.36 volts with the tube maxed out.
    There is a solid state relay (SSR) mounted on the big black heatsink that says “Danger High Voltage” in the picture. The SSR is on the side opposite the cooling fans and on the far left as seen in this picture. It has inputs labeled + and -. Connect the negative input of the solid state relay to ground (I used the chassis on the back of the PSU as seen in the picture – NOT the heatsink.)
    Hmmm... I believe this is already grounded on my unit, but I'll need to check that. (Maybe it's grounded through one of the other circuits on the extra control boards I have on the front of my unit.)
    The variable resistor R13 on the control board is said to regulate the tube current but I have not played with that yet.
    Which control board? I don't see one in your picture. On my unit I have three boards in front of the main PSU module that you show in your picture. Which of the three do you still have on yours? (Which one has this resistor on it?) Can you take a picture of it?

    I'm adjusting my tube current by using the aiming beam intensity knob on the face of the PSU. (You don't have this.) Also, if I select "continuous treatment" and step on the pedal, I can use the intensity control on the face to dial up the current. But since the aiming control does the same thing without having to hold the pedal down, I've been doing that instead.
    After my laser has been running for a minute or two the intensity starts to flicker mildly. The flicker seems to come and go randomly. My arrangement does not have optical feedback (yet) although the power supply does have this capability built into the control board. Maybe optical feedback would resolve the flicker???
    That doesn't sound good. I don't have any flicker at all. It could be oscillation in the plasma I suppose. Or it could be that you're right on the verge of loosing the beam because the mirrors are out of alignment, and slight thermal changes are enough to throw it out. When it flickers, does the plasma glow remain constant, or does the whole tube flicker? (Not just the beam, but the plasma glow as well.?.) If the plasma itself is going out, that's bad.

    Adam

  2. #32
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    Default HGM-5

    Adjusting the mirrors did seem to reduce the flicker some but not eliminate it completely. The flicker also seemed to decrease just as result of running the tube longer. The brightness appeared to improve some by adjusting the mirrors but not dramatically. The beam itself is bright enough with the Argon goggles on that I find it difficult to see the glow in the tube but I think there is some flicker there too.

    Until today I did not run it for more than a couple of minutes at a time. Today it ran happily for about 45 minutes. Without focusing the beam it makes black electrical tape immediately smoke and burns a hole through in about 3 or 4 seconds. No idea what that might be in mW.

    There are three circuit boards in my basic power supply. The igniter board is on the left side and two more boards are in slots on the opposite side. Of the two in the slots the one closer to the center of the PSU is labeled "Drive Board". The other, on the outisde of the PSU is labeled "Control Board". Here is a picture showing the control board in the foreground.
    PIC_0135.JPG

    On top of the control board are two LED's. One for the +12 volt supply and one for -12 volts. Near those LED's are two multiturn pots labeled R2 & R13. Another guy who has an HGM-5 says that R13 adjusts the tube current but on mine it has no noticeable effect - at least in terms of apparent brightness of the beam.

    The ignition coil is the white hand wound coil on the right side of this picture.

    After about 45 minutes of continuous operation, and without any warning, there was a very loud pop, a nasty smell and some smoke. The next picture shows what I found

    PIC_0136.JPG

    Now it seems I am in the market for two (or maybe more) MJ10005 transistors.

    In retrospect, seeing that R13 did not appear to control the tube current I don't know what, if anything, was regulating the current other than perhaps the maximum capacity of the HGM-5. If it really was operating flat out then perhaps that explains the demise of the transistors when it was otherwise working very well. Any other ideas what might have happened?

    Looks like there will be no more progress for a while until I can repair the PSU.

    Roger
    Attached Thumbnails Attached Thumbnails PIC_0135.JPG  

    PIC_0136.JPG  


  3. #33
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    Default Correction re HGM-5 PSU

    Regarding HGM-5 PSU:

    I made an error in a previous post about R13 controlling the tube current. That was from memory. The proper quote from my source is "R2 controls the output (clockwise is higher)".

    R2 & R13 are on the "Control Board" in slot J2 in the basic power supply. I don't know the function of R13 yet. It did not seem to do anything when I adjusted it on mine.

    Roger

  4. #34
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    Thats not a 5, its EDO-PC , which is NOT a cw tube, its a LONG PULSE TUBE. IT WILL NOT run CW at more then a few mW , yet can pulse up to 3 watts for 30 seconds, after which it needs a long cool down. Thats for eye surgery.

    I have a friend who is a career HGM factory tech, and I have seen those before.
    The tube is basically 2 60X tubes back to back with different gas returns and fill pressure for long pulse mode.

    with proper cooling the supply will do CW at just a few amps, but it can peak up for a few seconds to 15-18 amps.

    DO NOT ATTEMP TO RUN THAT TUBE AT MOR ETHEN SAY 20 mW CW

    the water cooling is small and closed loop, ie it uses A LOW CONDUCTIVITY , HIGH HEAT CAPACITY glycol for cooling, not h2o

    STEVE ROBERTS !
    Last edited by mixedgas; 05-03-2008 at 13:11.

  5. #35
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    [QUOTE=perseus;48385]Hi Adam and all,

    I am in Albuquerque, NM. Here is a picture of the PSU. I believe it is an HGM-5 because it seems to match pictures of other HGM-5 PSU's I have found and the control board says HGM and E5-00-07-057 Rev D. There are no other identifying marks I could find. I have made several photos but, as I'm not sure how welcome many large images are on this

    Perseus

    Thats a pc-edo, NOt a model 5, its a long pulse low duty cycle tube. IT IS NOT DESIGNED FOR MORE THEN 30 SECONDS CW, then a long computer controlled cooldown. ITS A POWER ON DEMAND SYSTEM, ie it fires each time the surgeon hits the foot pedal, then cools down, if you over drove it in surgical mode, it would beep at you when it was too hot and force you to let it cool. Since you have bypassed the medical computer, you can easily overdrive it. Ie it would do .5 second pulses all day, then as you increased the duty cycle, the system would srtart to back off. Factory test was 3.25 watts delivered, for up to 30 seconds, then cooldown. In eye surgery and dental curing, a more typical use would be 300 mW delivered, low duty cycle, .01 to 1 second pulses, at maybe 10-20 pulses a minute max till the close loop coolent got to hot, then it would back down. just adding better cooling wont help matters at all, a sthe gas pressure in the tube is NOT optimal for CW.

    Steve Roberts
    Last edited by mixedgas; 05-03-2008 at 13:03.

  6. #36
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    THE ATTACHED PICTURE IS A MODEL 5
    for the record
    a 905 is about 3 foot long and has a sqaure resonator with 4 rods in a scientific package with square mirror plates like a 60X or 532.

    See attachments

    I'll have my buddy send me a jpeq of a model 5 tube assembly.

    Steve Roberts
    Attached Thumbnails Attached Thumbnails model5A.jpg  


  7. #37
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    [QUOTE=mixedgas;49051]THE ATTACHED PICTURE IS A MODEL 5
    for the record
    a 905 is about 3 foot long and has a sqaure resonator with 4 rods in a scientific package with square mirror plates like a 60X or 532.

    See attachments

    I'll have my buddy send me a jpeq of a model 5 tube assembly.

    Oh and on HGM medical systems, if you have do not have a control computer and light feedback, the current will surge up to the maximum limit. The high limit becomes the current control. There are mods for this, but it is not easy, especially on a pulsed system.
    All medical systems are pulsed, and just about anything after 1995 are limited duty cycle, power on demand lasers that are not designed to run cw.

    Steve

  8. #38
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    Default HGM-5 vs EDO-PC ???

    Hi Steve,

    There might be some confusion because my PSU and laser tube are not a matched set. The tube is definitely an ALC-905 as you will see in the pictures below. It has large cooling fluid fittings (I assumed for water) and when operating CW the outflowing water is barely warm. I don't know what the optical power is but it is enough to make black electrical tape smoke almost instantly without any focusing. I ran it continuously at that output for about 40 minutes before the PSU died. The tube is 17 inches long (mirror to mirror) but there is a round mounting plate on each end adding 2 more inches to the overall length. I have been told that the electrical requirements of the 905 are very similar to that of the ALC-909 but otherwise I have been able to learn very little about the specifications of the ALC-905 tube so I would be very interested if any one has any details.

    The PSU is a little more puzzling to me. The only identifying markings are on the control and driver boards. They say "HGM" and "E5-00-07-057 rev D". The description of the PSU by the seller on EBay was:

    ************************************************** ***
    A power supply module removed from a small medical ARGON laser. It can sustain a current load up to 35A, and even higher intermittently! This powers the the 4W argon tube in my other auction. This is an unused spare part that will also run high power yag laser lamps!
    ************************************************** **********
    I got some schematics from Buffo (Adam) for what I understood was an HGM-5 PSU (although I see nothing on the schematics to show that that is the case). There are a few minor variations between my PSU and the schematic but they seem quite minor.

    Would more pictures help to clarify what this PSU really is? I can certainly make more pictures of the laser tube too if they would be of interest.

    I am very new at this and really appreciate all the advice I can get.

    Roger

    ps I posted pictures of a laser that really puzzles me recently. A search on Photon Lexicon for the words "mystery" and "dye" (and select show posts) will find it. Any thoughts on that one?
    Attached Thumbnails Attached Thumbnails PIC_0140.JPG  

    PIC_0145.JPG  


  9. #39
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    Perseus;

    The power supply you have is a pull from an HGM-5. No question about it. I saw the auction on E-bay where you bought it. (I actually considered bidding on that auction myself. I was watching it the whole time, which is why I mentioned the name of the seller you bought it from in my earlier post to you above.)

    The power supply in that auction (which is the one you have) is *identical* to mine, except that your unit has been stripped out of the HGM-5 housing and all the circuit boards for the front panel have been removed. (All the head interlock hardware, including the fiber launch interlock, has been removed as well.) But all the main PSU components are in the same position and are labeled the same as mine.

    What Steve (Mixed_Gas) is talking about is the tube... He believes that it's not really an ALC 905 tube, but rather a different model that isn't designed for continuous operation. As for me, I can't tell one way or the other, because I've never seen one. I know it's not an HGM-5 tube, and I know it's not an ALC 903 tube, but beyond that I haven't a clue. Still, it does seem odd that the name plate on the thing would be wrong... Maybe Steve can offer some clarification on that part.

    If it is indeed a tube that is designed for pulsed operation using a closed-loop glycol cooling system, then you might damage the tube if you run tap water through it. (Depending on the hardness of your tap water.) However, I was under the impression that as long as you kept the tube cool and the plasma away from the bore, you would be OK. Again though, I'll defer to Steve because he's the expert when it comes to ion lasers.

    I was able to identify the two resistors you mentioned in your earlier post. I haven't played with them yet to see what they do, however. Maybe tomorrow. (I'm just getting over a terrible cold, and I'm not back to 100% yet.)

    Adam

  10. #40
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    Default

    Subsea engineering ... sounds like this was built for some underwater project, thus requiring water cooling. Soemtime ago there used to appear argon lasers on eBay, housed in sealed steel cylinder similiar to pressure tank. But what purpose of having an underwater argon laser ? Rangefinding ?

    Piotr.K

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