Need help starting an ALC-60X Argon

[bungy]

This laser used to fire up fine. I have not started it in many months and now it won't start *hangs head in shame*.

I read the part in Sam's FAQ about starting it with an Oudin coil. I have the coil, but can't figure out exactly what to do.

The FAQ says to provide a weak spark to the cathode end "at the gap or junction of the ceramic tube and where the heat sink fins are brazed to the tube at the cooling riser box. There is a little strip of bare ceramic there"

I'm not sure which side is the cathode side, but I think it is the side near the umbilical cord in the pic. I also can't really tell which part is ceramic.

Does anyone have firsthand experience with this procedure? And can you walk me through it?


argon.jpg

[NobleGas]

The cathode end is the end of ythe tube with the 2 standoffs connected to 2 thick wires, nearest the umbilical on the ALC60X as you pointed out.
The ceramic section is the bit where the thermostat is attached, jut before the box section air duct. It's normally white or off-white in colour.
Before you start trying to start it with a coil, check exactly what the tube is doing first.
1. Is the filament lit? You should be able to see a yellow glow through the brewster stem at the cathode end.
2. If the filament is lit, do you hear a ticking sound after the warmup delay (about 1 minute, depending on the PSU)?
3. If the igniter is ticking, does it carry on ticking or does it stop?
4. Is the tube lighting up but no laser action?

[bungy]

Thanks for the response.

1. Not sure, didn't check
2. I do hear the ticking sound (Omnichrome 155 PSU)
3. The igniter just carries on ticking
4. Usually the tube does not light up. Over the past few weeks I have been messing with it, sometimes the cathode side flickers for a long time and occasionally will stay on solid, but the anode side does not light up.

[buffo]

I've done this to a Spectra-Physics 161 by literally placing the tip of the BD-10 on one of the cathode leads and pushing the button. It's probably not the best for the filament drive circuit, but my power supply survived the event. Your mileage may vary.

If the tube is merely hard to start (slightly high pressure from sitting too long), this should get it running. Once it's lit, run the tube at medium to high current for several hours (like, all day) and then see if it starts on it's own. Note that if you have developed a slow leak, the tube may be on it's last legs. In that case you may be able to get it started using the oudin coil for a little while, but eventually the pressure will get high enough that you'll need a new tube...

Before you try the oudin coil though, I would first check that the cathode is actually lit, as Noblegas suggested above. (Look for the soft yellow-orange glow right after you power it up. Turn off the room lights and you should be able to see it on the cathode end.) If the cathode isn't lit, you won't be able to get the tube to lase, so you want to be sure you have a hot cathode first.

Adam

[bungy]

It appears the heater is functional, cathode is on the right side in the pic. I could also see anode flashing purple as it tries to start.

My BD-10 doesn't have a button, I feel like I should make some kind of momentary footswitch before I attempt this.

20180603_160812.jpg

[bungy]

After leaving it on for an hour, the cathode side is lit. The anode side is still trying to start, it is flashing purple weakly.

I'll let it run for awhile longer and see if the whole tube light up.

20180603_170838.jpg

[NobleGas]

If you have a discharge at the cathode then the tube has struck; however, if the discharge isn't getting to the anode, it's finding another current path. How much current is the tube drawing in that condition?

[mixedgas]

Please see attached photos.

YOU have about 30 seconds after It starts to get the lid on. Once it starts, if it starts, give it a good 2-3 hours of running without shutting down.
`
You want to gently spark near the white ceramic tube body at the fin / ceramic weld. Not on the cathode end bell, but the fins inside or at the cathode side of the cooling fin box.
~
Do not spark the cathode lead on a ALC product. The spark should arc toward the cooling box. You can also try the same spot at the anode end. Warning high voltage at many,many amps is preset inside the head. Be careful. Keep the sparks off the light sensor card inside the head, the little 2n2222A transistor and the op-amp cannot take a hit.
~
Steve

[bungy]

Please see attached photos.

YOU have about 30 seconds after It starts to get the lid on. Once it starts, if it starts, give it a good 2-3 hours of running without shutting down.
`
You want to gently spark near the white ceramic tube body at the fin / ceramic weld. Not on the cathode end bell, but the fins inside or at the cathode side of the cooling fin box.
~
Do not spark the cathode lead on a ALC product. The spark should arc toward the cooling box. You can also try the same spot at the anode end. Warning high voltage at many,many amps is preset inside the head. Be careful. Keep the sparks off the light sensor card inside the head, the little 2n2222A transistor and the op-amp cannot take a hit.
~
Steve

Thank you, that is crystal clear.

I have worked with high voltage before (CRT monitors), but not high amps, and I am hesitant to start the tube this way.

I might set up a rig so I don't have to hold the coil.

Will report back when I get a chance to try this.

[mixedgas]

Thank you, that is crystal clear.

I have worked with high voltage before (CRT monitors), but not high amps, and I am hesitant to start the tube this way.

I might set up a rig so I don't have to hold the coil.

Will report back when I get a chance to try this.

The probe on the tip of the BD-10 coil is capacitively coupled by a thick Ebonite insulator. Stick probe in and go.

Steve