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Two Melles Griot Tubes With Clipped Chords

SKeeZ

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Hello again LPF,
This post is an inquiry about how easy it is to fix a problem such as this:

This eBay listing is pretty cheap and includes 2 melles griot HeNe tubes, the
only problem is that the wires have been clipped. how easy would it be to
strip the casing of the tubes, remove the clips from the anode and cathode,
solder new wires to the clips, and get the tubes running again?

Here is a picture of the tubes and thier clipped leads:

17986-4.jpg
 
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Speedy78

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Depends what tools you have at hand. I cut off both ends with a dremel. Sometimes you can just lull the caps off and work the tube out though. Just be gentle.
 

SKeeZ

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i have tons of tools at my disposal. look like i'ma make a bid.
 

Speedy78

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You will have to find a power suply to run them too. Dont forget the ballast resistor in the tail cap.
 

SKeeZ

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oh this is not problem, i am just worried about coaxing the thing out... what if say it is glued/lodged in the tube?
 
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You should be able to strip what's left, and solder on. As for the one just next to the endcap, you may have to remove it.

MG caps are held in place with very sturdy glue. A vice and some elbow grease can get them out.

When you strip the wire, you will only find one insulated wire, and another one bare. The bare wire is your cathode connection, the black insulated wire is your anode.

Also, given that they look pretty banged up, you should test if it's in pieces or not.

If you hear clanging around right off the bat, they are toast.

However, if they sound good, then you have one more test. Hold them up vertically to your ear, and tap/bang on the case. Lightly. If you hear a clang, even subtle, it's a problem.

In this case, your bore is no longer attached to the anode, it is just loose in the tube. Again, it is shot. Although with a cheaper, lower output PSU, you could make a lamp. Though that's a project for another day.

Good luck!

EDIT: Yes, MG tubes have their ballast resistors in the tailcap. So this is another precaution. When removing the cap, don't be so rough as to rip these components apart.

With other tubes, such as Uniphase for example, you will find the ballast resistor on the OC end (out end) so it is not a problem. Also, the caps of these are held to place by 4 small set screws (4 each end) and are much easier to remove.

The cathode connection runs from a wire, to the endcap, and there is a metal strip inside the endcap, boom! Cathode connection.

Just recently, made a tube work without the end cap with some laser surgery.

Anything is possible with determination! Hope these work for you!
 
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SKeeZ

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Its lookin like i'm gonna get them for just about 10 bucks +shipping so screw it, if it doesn't work, oh well. can anything be done with the OC or HR or are they in place permanentley? (is an external cavity possible if i should get these tubes working?)
 
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Mirrors are cemented on. So they're not going anywhere.

If they're working, then of course you can do external cavities :)
 

SKeeZ

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woah. my mind was just blown. i though an external cavity was an extension outside of the tube, between the OC and HR. i thought to have an external cavity you needed at least one end without a mirror. I guess my whole understanding was wrong?
 
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That's the ideal method, but adding a third mirror works too. You're just taking the light from the other mirror, and trapping 99% of it again, just like the internal gain.

Watch the video I posted :) No brewster plates :)

I don't own any brewster tubes yet.
 

SKeeZ

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Cool. i suppose that makes a lot of sense. what would happen if you had a brewster tube and had two HR's to resonate? just a funny question i guess. on a more serious note, are most of the HR's in these tubes broadband HR? if not could you add a broadband OC with a broadband HR in series with the 632.8 HR and achieve resonance of multilines (If they exist).
 
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Question 1: If you added one mirror, and another in front of it? Well. In theory, of one mirror only did yellow, and passed red, and you added another mirror for red, but passed yellow, then you could theoretically get both yellow and red to resonate.

Question 2: Most HRs are not broadband for the spectrum you want. For instance, red mirrors will be broadband >632.8nm. Rather than <. So you cannot get the orange, yellow, and green.

If one mirror is broadband, and the other is not, you can put a broadband mirror in front of the non broadband.

If neither are broadband, you can use two mirrors. I did that in the video, and explained it too, tsk tsk :p

The theory is that if the mirrors already in place are high transmission for those lines, they will not lase. By placing mirrors with a high reflectivity at those other wavelengths, you are thus creating a second cavity that goes from one external mirror, to the other.

So you now have the original cavity for the original mirrors, and now a second one that passes through the original mirrors. Though you are still using the same light created by the ionization of the atoms in the tube, so you will not get more output by creating a much larger cavity.

So in a nutshell.

The process taking place in the tube is creating orange photons. The mirrors in place pass these photons.

So now you have these 611.8nm photons hanging out, being created by Ne+ and all that. They start shooting out from the bore. They pass right on through the original mirrors, then they hit your external mirror, and reflect back through the other mirror, back through the cavity saying hello to their 632.8nm brethren, then back out through the other tube's mirror, and finally reflect off of your second external mirror.

So now you have two cavities overlapping, created by the same light source :)

SCIENCE!
 
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SKeeZ

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yet again, gas lasers become even more interesting.
 

SKeeZ

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ikr. I made my first diode laser a few months ago and did some burning stuff but then... it wasn't quite as fun as when i first got it... HeNe's are so much more interseting.
 
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Just make sure to do the proper amount of research to understand what you're getting involved in :)
 




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