writes:

On 07 Apr 2013 16:40:53 -0400, (Samuel M.
Goldwasser) wrote:

writes:

On 06 Apr 2013 16:45:28 -0400, (Samuel M.
Goldwasser) wrote:

I'm trying to repair some old helium-neon lasers for a physics lab
(155SL Uniphase and 155 spectra physics). Is it possible to find
replacement tubes for these lasers?

The 155SL uses a JDSU 098 or similar long barcode scanner tube. These
are readily available. I may be able to dig up a couple.

The 155 uses the old 060-4 side-arm tube. Electrically, it can also probably
use the 098, but fitting it in may be a problem.

It may be better to simply buy some more modern HeNe lasers surplus. I have many
available, though probably not quite as cheap as eBay.
Greetings Sam,

I wondered if you might reply to this thread. Part of the welding I do
in my shop is TIG welding and I do use helium sometimes. I also have a
laser tube, the bar scanner type, that doesn't lase anymore even
though the power supply is fine. If I was to put the tube in a
pressurized vessel of helium do you know how much pressure and how
long a time it would take to refill the laser tube?

Do you have an idea of the make and model of the tube? Most of these
are hard-seal and never suffer from He depletion. And even those
that have Epoxy seals often leak air in more quickly than He out.

However, you have He and nothing to lose, so put it in a bag of He
at atmospheric pressure for approximately 1 day per year of age.
So, if it's about 20 years old, try 3 weeks. Remove it and test
periodically. If you go overpressure on He, there's no way to get it
down quickly.
I have no idea of the make and model of the tube. I bought the thing
at least 20 years ago from a surplus store. This was when the used
hand held bar code scanners were just starting to show up at
electronic surplus stores. That laser was the coolest toy. I was very
careful with it because of the high voltage and the laser light. I did
machine up a new housing for the tube because the original one was
cracked. I believe the tube is a hard seal tube though. I don't
remember seeing any type of epoxy plug. I know the power supply is
still putting out high voltage because it will arc to ground if the
wires are removed from the laser tube. Maybe the start circuit is bad
or something if helium won't leak through glass.

Sometimes it takes awhile to start, especially if it hasn't been used in
20 years. Shining a light on the tube can may help.

Take some pics.

--
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