View Full Version : Problem tube or Power Supply or Both?

Brent Ramsay-Boyd
10-17-2016, 7:31 AM
I am having some firing issues with the 80W Reci Tube on my Shenhui SH1390 Laser Cutter.

I am almost certain that the laser tube has seen its end. I have had more than one tube fail prematurely, the current tube has maybe 200-300hrs on it, but what I want to know is could the power supply also be causing a problem, or have I just had bad luck with tubes.

The tube has never been run without cooling from a proper cooling pump, and I have always run the tube under the 28mA's recommended by the manufacturer. I have run this tube at a max of 26mA.

I have added 2 video's of the tube running and the ammeter output.

Running a solid line file on the laser the laser tube starts off very unstable, and then seems to stabilize after a while, although I suspect even after stabilizing its not very good quality. Is this definitely the sign of a finished tube, or could the power supply be the culprit? The ammeter output has also decreased from 26mA - 21mA over a few days while the machine has been sitting unused.

My question on the ammeter is, when the laser fires, the Amp reading spikes well above the settled value of 21mA in the video, is this normal? Could these spikes be causing the shortened tube life?

I do not want to replace the tube before confirming that there is nothing shortening the life of my tubes.




Kev Williams
10-17-2016, 12:24 PM
How does it act during raster engraving? I'm just curious as to if the laser will fire reliably while engraving text-- whether it does, or not, may provide some insight...

Matt McCoy
10-17-2016, 3:16 PM
I would unplug and let the capacitor discharge for about an hour, then check the connections and wiring to the tube. If you're replacing tubes prematurely, I would suspect the power supply.

Martin James
10-24-2016, 9:33 AM
Some of those lasers have a button you can hold down to fire the tube. If there is an issue with your file than the button would bypass that.