🚀 go-pugleaf

In article <massoud.57@chemteca.sdsu.edu>, massoud@chemteca.sdsu.edu (Massoud Ajami) writes:
> In article <1992Aug26.043710.27944@vpnet.chi.il.us> cgordon@vpnet.chi.il.us (gordon hlavenka) writes:
> 
> >I have an _ancient_ laser which almost works.  It's a HeNe laser,
> >model 3100 from Gaertner Scientific (circa 1969).  It worked for a
> >while, but now has developed an electrical problem.
> 
> >This laser, when you get down to it, is basically an expensive beer
> >sign with a couple of mirrors hung on it.  The tube does not run
> >continuously any longer.  It flickered for a while, and now it just
> >fires in bursts.
> 
> >The power supply consists of 2 transformers, 4 diodes, 6 resistors,
> >and 2 big capacitors.  My first guess is that the caps have become
> >leaky.  Any tips?
> 
> >It _does_ lase, when the tube fires.  So the optics are OK.
> 
> >(Yes, I know that for $50 I can buy a semiconductor laser with more
> >power and a better beam shape.  That's not the point.)
> 
> You have lost the gas. You woudln't expect helium gas stays in the 
> tube forever?
> 
> Peace and Prosperity!
>   ---==< 110 >==---

While loss of gas will change the tube running voltage, it's unlikely
that it would lase after losing that much gas.
When a laser has lost its helium, the plasma when viewed from the side
will be brillian neon orange.  A properly functioning HeNe will be orangish
yellow. A tube that has taken in air or water will be purple.

I've seen ballast resistors open before.  This would cause the symptoms
you describe, because the voltage will rise until it can arc over the
gap in the resistor, but the power supply can't sustain that voltage.  A
good ballast resistor will be around 50K to 150K ohms.


Michael MacKenzie	(Purdue University Unix Group)
mm@mentor.cc.purdue.edu