What do I need to make these lasers work?

[mixedgas]

Looking at the picture, and make sure there is a working fan on the argon tube , do the following in sequence That tube needs at least 250 CFM of air across the fins at all times.

This is a educated guess, assuming there are no hidden controls, teh psu works, and the blower is still mounted on the laser. Proceed at own risk.

initial state
all switches off

turn on fan
turn on 3V,wait sixty seconds for warm up, cathode in argon tube should glow
turn on "tube"

usually on a nec its
blink, blink, blink, light. make sure something blocks the beam and protect your eyes. tube may light at that point, as NEC starters are automatic and in the head. If more then 8-9 amps after about 2 seconds, shut down right now by turning off "tube" NECs die fast (as in seconds) from overcurrent.

If it runs, has cooling, and its less then 8 amps, leave it run a few minutes

SHUTDOWN SEQUENCE.

Turn off "tube"
wait 60 seconds to prevent shock to cathode glass to metal seals
Shut off "3V"
wait 30 more seconds
turn off "FAN"

remember, dang, do not look in laser with remaining eye!.

The round plastic 9 pin connector is a amphenol CPC , aka circular plastic connector, available from DIGIKEY in the states looks like a standard sex 9 pin series one CPC, you need to order pins and a shell when you order the connector body You'd need a flanged receptical to mate to the one your holding up in the picture,

Steve Roberts

[TheYellowDart]

mixedgas: Thanks for the try, but that didn't work for me. The laser didn't fire and no current was drawn through the ammeter. I couldn't tell whether the cathode had begun glowing yet or not. Is it safe to do this while the cover is off if I don't have protective glasses?

I tried doing this with both large power supplies and one of the argon tubes. I didn't try with the other as I noticed there are some wires inside which have been cut and I want to suss out what they are for/why they've been cut.

On one of the lasers (the one without the cut wires) When the offset knobs on the power supply were turned there was no movement of the galvo's. When this was done for the other laser (before I realised there were cut wires inside) the galvo's did move. Not sure why this would be and will look into it, though at the moment I'm more interested in actually getting the lasers to fire.

There doesn't seem to be any means of blanking in the units, but I'm unsure as to how this is usually achieved. Regardless I can't see a way for the light to be blocked off.

I noticed a couple of wires today which interested me. They run from two female ports at the back of the laser which take what looks to be 3.5mm audio jack style plugs and run to a small (about 1cmx1cm) component just at the point where the beam exits the laser side of the cabinet towards the mirrors. What would this be, and what's it for? On the laser with the cut wires, it is missing (though once was there and has been removed as there is remnants of the glue and drilled hole still there). You can see about half of it in the following picture, I'll try and get a better one later.



Also in that picture, what would the solenoid in the same area be for? The plunger doesn't move anything around it physically.

Pretty buggered today, so that'll be it for the moment. Later I'm going to hook a voltmeter up to the leads for the laser and see what's coming out of the power supply.

Cheers, Dart

[Edit: It also occurs to me that I should probably ask what voltage I should be using on the variac which leads to the power supply (or whether I should even be using it at all -- everything was included as a "kit" for these lasers so I've been trying to use these pieces as such). Up until now I've been trying a few different voltages (110v, 200v, 240v and some random ones around) as my friend said when he was shown them working they had it at about 200v but again I really don't trust his memory. How would I go about finding out what input voltage I need to use?]

[buffo]

I couldn't tell whether the cathode had begun glowing yet or not. Is it safe to do this while the cover is off if I don't have protective glasses?

I'll field this one. Yes, it's safe. The glow of the cathode is harmless, as is the bright discharge of the plasma tube itself. Coherent light is only emitted from the output coupler (the partially reflective mirror at the front of the tube) in a narrow beam that is parallel to the long axis of the tube, though to be honest it's not uncommon to see a very weak beam also be emitted from the high reflector (the fully reflective mirror at the back, or wide end, of the tube). So long as there isn't anything reflective in the beam path that could deflect the beam up into your eye, you should be fine. (Be careful around the galvos; that's where a small movement of the galvo shaft can move the beam around a lot.)

There doesn't seem to be any means of blanking in the units,
<snip>
I noticed a couple of wires today which interested me. They run from two female ports at the back of the laser which take what looks to be 3.5mm audio jack style plugs and run to a small (about 1cmx1cm) component just at the point where the beam exits the laser side of the cabinet towards the mirrors.

From the description and the location in the beam path, I'd say it's an AOM, which is used for blanking. You send RF into a crystal to make it vibrate and it sets up a standing wave inside the crystal that refracts the light slightly. So you can slew the beam to one side by a few degrees. Just enough to miss the pinhole in the output port. AOM's operate very fast and work well for blanking a single color beam from an ion laser. (PCAOM's, on the other hand, can handle multiple colors at once.)

I can't see the module in the picture you posted, but I do see a mount where it probably was located. Also, the solenoid you mentioned is probably a beam-blocking shutter. It's a safety feature. (It's possible that the flag on the end of the solenoid shaft fell off.)

Adam

[TheYellowDart]

Small update. After a few hours of fiddling with a friend (thanks Jack); sussing out what does what, checking voltages etc. It quite abruptly dawned upon us that the cable we were using was entirely missing the pins required to transport both the 150v DC from the power supply over to the step-up transformer for the laser and the 240v AC which leads to a step-down transformer to 3v AC for the cathode element.

Seems this whole time I'd been using a cable which only had the control circuits wired up! I'm guessing it was used for testing only.

A quick drive home to pick up the rest of the cables and we were in business (sort of). With the new cable following the start-up instructions provided by mixed-gas the element does start glowing, however when the tube switch is flicked it arcs repeatedly (a wonderful blue-purple light) but can't sustain the lase. When it does this it pulls between 0.5 and 3 amps, which coincide with the brightness and length of the arc (longest one would have been about 1/3 of a second, though most are a lot shorter).

We tried leaving the cathode coil energized for a while (about 5 mins) as per the suggestion on Sam's Laser FAQ to no avail, though he doesn't quantify "a while". He also suggests the use of a Tesla coil for initial ignition, but I don't have access to one. Will look into it further later, don't have much time but this is just a heads up post to let you know where I'm at.

I have a few questions about the laser which has some cut wires inside, but I'll get to that later.

Dart