Old laser i bought for US$14, any good? (with pics).

[Psi]

I've been reading this forum for a while, lots of interesting stuff.
I don't know a huge amount about lasers, i have a 300mW red laser i made from a 22x speed dvd drive diode and I had an old 1mW HeNe many years ago.

But today i came across this at a HAM-radio-group parts(junk) sale for $14 and couldnt resist.

I dont know if it goes (the guy said it went when he powered it up many years ago). To be honest, I dont really mind if it's dead as there's well over $14 worth of parts i can salvage from it.

The label says 400mW but the guy had labelled it as 80mW. (perhaps it's just so old the output has fallen?)

It's obviously been modded to hell with an external power supply and before I plug it into the wall and see if it explodes or runs i figured i'd post on here and get some info about what it is and how to safely test it.

I have a degree in electronics so any technical info is most welcome.

Here's all the pics...

[Psi]

-Update-

I did some googling and found this laser which looks very similar

http://www.fullof.info/argonlaser/

[buffo]

Yeah, looks like an NEC air-cooled head with a hacked power supply. Over 8000 hours on the meter means in might not have a lot of life left unless it was run at very low current all that time.

Before you fire it, you'll want a large fan (equal to the size of the one blowing on the PSU in the picture you posted) drawing air up through the cooling fins on that tube. If you don't have the cover for the head, you'll need to make some sort of duct for it.

If the tube is in good health, you might get 100 mw or more (all lines). If it's near end of life you'll be lucky to get 20 mw. Still, for $14 you can't loose on this deal.

Adam

[Psi]

thanks,

yeah, i have the cover with the 2nd fan, so thats all sorted

When i fire it up, what signs am i looking for that say....
... "quick, kill the power, she's about to explode(burn out)?"

Should it emit light instantly or take a while to warm up and output ?

It looks like its wired with 3VAC on the heater, 80VAC on the 110V input (runs the fans and hour meter) and the same 80VAC rectified to 113VDC running the HV psu

The 3x 1ohm resistors seem to be in series with the 113VDC feed (lowering the voltage once it strikes maybe?)

[Laser Ben]

It should emit light quickly without much delay. You will be able to tell if the heater is going then you should hear it click to ignite.

[Psi]

I just powered it up.

It took maybe 4 seconds for the heater to warm up, then it started.

The only output is violet and very dim and out of focus.
You can see it on an object at a few cm away but after 50cm the beam width is maybe 2cm wide and impossible to see.

I dont think it's lasing. The light emitted doesn’t look very laserish.
I dont see any speckle pattern in it at all. I'm thinking this light
is just the glow from the gas.

Does that sound right?

The mirrors could definitely be out of alignment as the laser could easy have been dropped or had it's alignment tampered with. (I think its had many owners)
I've had a read of some guides on doing argon mirror alignment and it seems time consuming but simple enough.

Any thoughts/ideas?

here's a pic of it running (dont worry, i didnt run it without the cover for more than 20 sec.)

[Psi]

and the light coming out of it.

[Psi]

-Update-

I found if i pushed/pulled a little on the front alignment screws it would start lasing. So with some alignment screw tweaking and a multimeter on the optical power pickup i got it working and tuned it for max power.

I dunno what that power is though.

[Carl B]

Well done. A very nice little laser for just $14.

Carl

[Psi]

yeah, im not too sure what to do with it now.

Guess i'll mount the power supply in a case and tidy up the wiring.