I can see it glow....but nothing comes out the end

[Richard DiMaggio]

I have a home built 40 watt CO2 setup. My original setup was a used Synrad 25 watt tube that eventually out, and at nearly $800 + shipping there and back to get it repaired pretty much forced me to go with the Chinese glass HV tubes. I have been using this setup now for over 2 years without failure. Until now. I have read a few of the answers posted about "laser not firing" but most of them were either power supply problems or misalignment issues. When commanded, this tube glows the pretty purple, just like it has always done. I can turn up the power to it and it glows more intensly. However, holding a piece of paper at the outlet of the tube shows nothing. I did read where Dan suggested that it could be the exit mirror out of alignment (and I understand that there is no effective way short of taking a glass blowing class that it can be fixed) but I would think that with all those photons bouncing around inside the tube that SOMETHING would make its way out the exit mirror....
Dan? Rodney? Any suggestions or should I donate this tube to the glass recycle bin too?
thanks guys.
rj

[Neal Schlee]

I have a home built 40 watt CO2 setup. My original setup was a used Synrad 25 watt tube that eventually out, and at nearly $800 + shipping there and back to get it repaired pretty much forced me to go with the Chinese glass HV tubes. I have been using this setup now for over 2 years without failure. Until now. I have read a few of the answers posted about "laser not firing" but most of them were either power supply problems or misalignment issues. When commanded, this tube glows the pretty purple, just like it has always done. I can turn up the power to it and it glows more intensly. However, holding a piece of paper at the outlet of the tube shows nothing. I did read where Dan suggested that it could be the exit mirror out of alignment (and I understand that there is no effective way short of taking a glass blowing class that it can be fixed) but I would think that with all those photons bouncing around inside the tube that SOMETHING would make its way out the exit mirror....
Dan? Rodney? Any suggestions or should I donate this tube to the glass recycle bin too?
thanks guys.
rj

More than likely Dan's right. I've spent many hours over the years trying to get an exit beam after rebuilding our 2 Apollo 80 watt lasers and on these lasers both mirrors are adjustable. Getting output is not the only issue, you want max power and a good beam mode. If your tube does not have adjustable mirrors you're pretty much SOL. Glass tube Co2 lasers can be very finicky, as output can be affected by mirror movement, temperature, pressure from mounting, gas quality etc. Our tubes were cushion mounted in a heavy alm. extrusion, just tightening the extrusion to the frame would vary laser power, so much so, that at times this is how I tuned the tube.

Personally I'll never own another one, it's been metal tubes for the last 15 years for me.

Neal

[Rich Harman]

Personally I'll never own another one, it's been metal tubes for the last 15 years for me.

Is it possible that glass tubes are less finicky now than they were 15 years ago?

Two years of good service on a cheap glass tube does not sound too bad to me. Heck, some multi-thousand dollar RF tubes don't last as long.

[Rodne Gold]

The bad news is that it sounds like it's a gonner.. the good news is a replacement should cost you less than $150.

[Richard DiMaggio]

Plus shipping...

[Rodne Gold]

Its a generic 40w tube , you should find local US chinese laser resellers stock it off the shelf.

[Dan Hintz]

When commanded, this tube glows the pretty purple, just like it has always done. I can turn up the power to it and it glows more intensly. However, holding a piece of paper at the outlet of the tube shows nothing. I did read where Dan suggested that it could be the exit mirror out of alignment (and I understand that there is no effective way short of taking a glass blowing class that it can be fixed) but I would think that with all those photons bouncing around inside the tube that SOMETHING would make its way out the exit mirror....

Sorry for the (very) late reply... been away from the Creek for a spell.

Junk it. The lasing action is created by a cascade effect... photons hitting molecules, creating more photons, etc. You have to hit a critical amount of photons, however, before lasing will start, hence the need for exact alignment. Once you're outside that critical alignment area, all you get is a few photons bubbling off here and there in non-aligned directions, but not enough to avalanche the entire system.