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Thread: HGM 5 - new toy for me, if I can get it to lase!

  1. #1
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    Default HGM 5 - new toy for me, if I can get it to lase!

    Hey everyone...

    Finally got my new toy. Yep - an HGM 5 medical laser. It's a photo-coagulator, or rather it was a photo-coagulator in it's previous life! I'm planning to modify it for CW operation.

    Background: The HGM 5 is a multi-line Argon laser that runs of single phase 220 Volt AC power and is air-cooled. The tube is similar to the ALC-68B, but with shorter brewster stems. In CW configuration, with a good tube and adequate cooling, you can get almost 1 watt (all lines) of output. In it's original configuration (pulsed operation) it will do 3.1 watts for up to 30 seconds, but then you have to let it cool down for 3-5 minutes... Thus part of the modification for CW operation includes adding lots of extra airflow around the tube.

    Unfortunately, after I unboxed the thing and hooked iut up to my dryer outlet, I discovered that the damn thing won't lase! It won't even light the plasma in the tube. I'm pretty sure it's an interlock problem though, because everything else is working OK and the guy that sold me this laser agreed to a 30 day warranty, so it SHOULD work...

    Sigh... I've asked a few smart folks on alt.lasers for assistance; hopefully I can get this figured out soon.

    Anyway, for some pics of this thing, have a look at the album I set up in the gallery...

    Adam

  2. #2
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    Looks like a new toy for Adam..Kewl

    Have fun, .be careful
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  3. #3
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    Looks cool..Does it have a cover?? Did you try it with the cover on..? Pic three shows that it has a Lid switch..... ...
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  4. #4
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    Hi Rick;

    Yeah, I tried it with the cover on at first. When that didn't work I removed the cover and bypassed the lid switch with a clamp... I was hoping to be able to see at least evidence of a discharge in the tube, but no luck! No plasma...

    I hope the issue is something simple like an interlock wire somewhere that has fallen loose, but so far nothing looks out of place.

    Oh, and I've got a pair of OD15 (!) broadband argon goggles to wear whenever I fire this thing up. Truthfully I'm a little afraid of it; did you notice the size of those capacitors in the last pic? (The one labeled "innards"?) Those things are the size of a can of soup! I bet they'll hold a charge for MONTHS... So I'm very careful when poking around inside the PSU. Likewise, if I ever get it to lase, I'll be equally wary of the beam. (Don't want to photo-coagulate my retina!)

    Adam

  5. #5
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    did you mod the powersupply from 220volt down to 110volt ? you say...


    I have 220volt where I live :roll: so if you shipp it to me I`m suuure I can test it for you :P :P

  6. #6
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    Default HGM 5 voltage

    Liteglow;

    No, I haven't modified anything yet. The laser operates on 220V single phase AC. Most clothes dryer outlets and cooking stove outlets here in the USA are wired for 220V. It's only the regular wall outlets that are wired for 110 V here. (Yeah, I know that most European nations run 220V to all outlets - I was a foreign exchange student when I was in high school and actually lived in what was then West Germany for 6 months...)

    In pulsed operation, the HGM 5 can draw up to 35 amps, which is more than the dryer outlet can provide (it's a 30 amp circuit). But I don't intend to operate it at full power; I just want to test it to make sure it works before I start making changes to the power supply.

    To modify the laser for continuous output, the computer-controlled dose circuits have to be bypassed. Then I need to find the current limit circuit, and install a potentiometer to limit the tube current. (I also need to install more fans.)

    I expect I'll be running it at around 18 amps of tube current, which should be good for 600-900 mw or so, depending on the condition of the tube. I figure with 18 amps going down the tube I won't be pulling more than 25 amps or so from the wall socket, so I should be fine if I run it off the 30 amp dryer circuit.

    Shipping on this laser is *really* expensive. It cost me 90 bucks to get it sent to South Carolina from Minnesota! Of course, the thing weighs like 85 pounds...

    If I can't get it working, I know someone in Charlotte, NC that may be able to help. But if that doesn't work, I may have to send it back to Minnesota. (It came with a 30 day warranty.)

    Adam

  7. #7
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    Quote Originally Posted by Buffo
    Those things are the size of a can of soup! I bet they'll hold a charge for MONTHS... So I'm very careful when poking around inside the PSU.
    It would be a very wise idea to add some high value bleed resistors across the caps.

    Just out of interest, might there be some interlock at the fibre output?
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  8. #8
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    Default HGM 5 - no luck

    Dave;

    There is indeed an interlock at the fiber launch aperature. Fortunately, this unit was supplied with the fiber! However, the interlock is also easily bypassed by cutting the top off of the cap from a "Bic" ballpoint pen and shoving the cap into the aperature... (No comment on how I learned that little nugget!)

    Unfortunately, it seems there is a problem with the tube itself. I can hear the ignitor circuit pulsing, but there's no flash in the tube itself. Another laserist suggested that I connect a HeNe power supply across the tube and look for a dull glow of plasma down the bore. (I used a camera!) No plasma... No arc... No glow. (damn...)

    It looks like this one is going back to the surplus dealer. (Which totally sucks, since I've already invested several hundred bucks buying wire, plugs, outlets, fans, and other crap that I would need to get this thing working CW - now I'm stuck with all this stuff!)

    Adam

  9. #9

    Default HGM tube

    I'm seeing quite a few HGM-5s on ebay... usually around $500 for an un-modded unit.

    Most of the ones you find have been in storage for many years and suffer from over-pressure. I would suggest hitting it with a tesla coil to see if it's vacuum-intact. The HGM tube is big enough that most HeNe transformers would have little effect on it, especially with an over-pressured tube. If you still have it and you know anyone with a small Tesla coil it's the best way to find out if it's dead.
    I'd be interested in any new info you have....

    Did they take it back?

  10. #10
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    Default HGM-5 laser problems

    Hey Eyecage;

    I agree that $500 seems to be the price point for these old HGM-5's. Unfortunately, as you mentioned, many of them have been left idle for too long and are now high pressure. It's really stupid, too, because the manual specifically warns you to power the laser up every 2 weeks to prevent this from happening. I guess no one reads manuals anymore.

    I tried the HeNe psu trick at the recommendation of Sam Goldwasser, but he also suggested that a telsa coil would be better. (I don't have a telsa coil, which is why he suggested trying the HeNe psu.) I think he assumed my HeNe psu was capable of delivering a 14KV starting pulse. However, in reality the one I have can't deliver much over 7KV.

    I even packed the laser up and drove it to Charlotte, NC to have Dreambeamz look at it. (He's a member here on PhotonLexicon that has experience with both HGM-5's and ALC-68B's, along with lots of other, larger ion lasers.) He agreed that the tube is probably high pressure, though he did comment that otherwise the unit was very clean and looked as if it had not been used much.

    I contacted the seller about the problem, and we reached an agreement where by he would refund the $500 purchase price (but not the $90 shipping charge), and I would KEEP the laser. This made sense to both of us, since if I were to return the laser he would have to refund my initial $90 shipping, plus pay an additional $90 to ship it back to him, and in the end he has no use for a dead HGM-5 laser. On the other hand, I now have a power supply that can fire up an assortment of argon tubes, so all I need to do is purchase a replacement tube and I'm in business, all for just the $90 shipping! Not a bad deal...

    Of course, I have another $200 or so invested in 125 ft of heavy gauge wire and connectors so I can hook it up, plus another $100 for the high-volume muffin fans I bought to keep the thing cool... If I can't find a replacement tube, then all that money is wasted as well.

    Steve Roberts (of alt.lasers fame) had originally offered to help me out by selling me an HGM-903 argon head for his cost of $230. (He got it fron a surplus dealer.) Supposedly the 903 head has a tube very similar to the one in the HGM-5, but the head is separate from the PSU and comes complete with all the cooling fans built-in. (Evidently it's a rare beast - only a few of them were ever imported into the US according to Steve.) Unfortunately, I haven't been able to get Steve to return any of my e-mails for the last 6 weeks, so I believe that deal has fallen apart. (Sigh.)

    I'm still looking for a (cheap) multi-line argon tube that I can use with this HGM-5 PSU. I know that it will light a bunch of different tubes, including the Lexel 75, 88, and 95 tubes. I'm not really crazy about water-cooled tubes though, so I was hoping to find something closer to the ALC-68B...

    Adam

    <edit>
    PS: Here's another thread discussing the HGM-5 laser.

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