Aerotech hene

[phenol]

I recently acquired this He-Ne red laser. I cant tell the model number or manufacture date, but the warning sticker says 1.0mW max.
It is 220VAC powered self-contained laser with a beam shutter, TEM00 as far as i can tell.
Inside there are a step-up transformer and a voltage multiplier plus a HV NPN transistor for low side current regulation. Iop=4mA

It's a soft-seal tube with adjustable output coupler. There is some garbage around the getter, but it's still lasing at probably less than 1mw

 

[Sigurthr]

That is quite an insteresting little laser! You don't see a lot of soft seal tubes these days.

 

[Cyparagon]

HV NPN transistor for low side current regulation.

Any idea what it's rated for? I don't see HV NPNs too often at all.

 

[phenol]

MJE2360T, VCEo=350V, not heatsinked.

The tube flickered when the interior of the laser warmed up. The doubler electrolytic caps have all gone bad. I replaced them and it now works fine. the driver is rather low tech, i was hoping for something that can power the 5mw tube i have, but at 1800v it just wont maintain a stable discharge...
I tried to 'activate' the getter by inserting the tube in an improvised induction heater. i have no idea if it helped or not, but the glass above the ring got very hot.

 

[Sigurthr]

From what I've seen of getters getting induction fired they typically have to glow red hot before they will activate.

 

[phenol]

From what I've seen of getters getting induction fired they typically have to glow red hot before they will activate.

I'll try, but chances are that the mosfets will glow red hot before the getter...

 

[pschlosser]

That power supply section and tube look much like the Spectra Physics 155 we see in so many classrooms.

Judging by the length of the tube, it is hard to imagine that tube is spec'd for more than 1mW. That .9 drawn on the tube may suggest its measured output at one time.

The getter does NOT need to glow red-hot in order to work. But at lower temperatures, it takes longer to do it's business. Rigging up a magnifying glass to focus the sun past the outer glass tube and on the getter itself has proven effective on numerous occasions. The idea is to attempt to heat up the getter, without heating up the glass tube (too much) by making sure the focal point is on the getter and not the glass tube. It may take several "applications" using this method to get contaminants out.

Consider running the tube straight through for a week or two, if you have problems starting it. Running it this long may increase the output power by 10-25% (estimated.) Since the tube is likely rated in the 10 of thousands of hours, you don't have much to lose by burning her in and trying to clean things up a bit.

If you have an LPM sensitive enough at these low powers, you can try adjusting the mirror at the output end to see of you can increase it's output with a little tuning. If you're squeamish about that, don't worry. Brand new, this tube may have put out 1.5mW.

And that power supply section could last for many years. Nice find. How much did you pay for it?

 

[phenol]

around the equivalent of $50-60, i got it in Bulgaria. the guy might have settled for a little less, but wat the heck...

it starts normally with the new caps, i'll keep it on for a couple of days...

 

[norbyx]

The first thing that I was reminded of when I first saw the picture of this laser was my 6th grade class, I remember a very similar looking laser was taken in the class for experimentation.
Anyhow you got yourself one very nice little laser.... congrats.

 

[Cyparagon]

Seems kinda strange they're only using a 350V transistor considering the voltage of the load and starting pulse... but I guess as long as you don't short the output too often.

 

[phenol]

There is a 68k resistor across CE. The topology is the same as this one:
Sam's Laser FAQ - Complete HeNe Laser Power Supply Schematics