Tube or power supply?

New system build with a 50W tube, ruida controller. For short bursts everything seems to work. If I try to run a engraving (more than a couple minutes) it seems to stop cutting but the job is still running and get no errors. Tube still shines a nice purple when it thinks it should be running and meter says it is getting current. But if i set a piece of paper in front of the tube it get nothing.

If you are seeing purple it is firing. I would double check for loose mirrors or lens.

Weird part was I got a nice purple glow and no beam out the end of the tube. This morning I just went out and tested and i have nothing at all when I pulse form the controller or the test switch on the power supply.

so now its like a toss up… I feel like I have a 50/50 shot at guessing the right part… and I will most likely guess the wrong 50

Hummmm might want to check the safety switches before assuming is is a p.s. or a tube. The water flow switch could cause issue or a intermittent door safety switch as well.

yes I bypassed all the safety switches… and power supply test switch bypasses them as well… Would a bad tube still show current on the ammeter?

I dont know maybe a no contact voltage detector at the tube might show something.

Could it be beam alignment going off an a certain part of the work area? When you say you have the purple colour but no beam, are you checking at the output of the laser tube or at the final nozzle or after the second mirror say? It doesn’t take much misalignment to stop the beam coming out through the last lens.



It was no output from the tube before the first mirror. But now I get nothing.

Is the purple you are seeing still as intense as before or is it more dim?

Except the already mentioned checks, please also check the wiring for the tube. I had this once too and a bad connection resulted in a slight arc to ground. Might not be the case, but worth checking

ok I am leaning towards the power supply needing replaced. this morning voltage detector was lighting up when i put it near the HV when it fired… so this afternoon when i had time i ran a new line from the anode side just in case it was the ammeter. low and behold it fired from the test switch now but not from the controller. turned it all off and ran new in line from the PS to the controller since the old one was a temp one i threw on… now nothing again when i press the test switch on the PS or controller and no power registering on the HV line…

The PS is old and one of the cheapest you can get. so I think that will be the first to replace and see if that hopefully resolves everything.

You dont have any of the HV lines near a ground point? and the ground connection is clean?

Finally got the power supply in and had time to hook it up today. tube is firing and looks promising. Was able to just do a quick light engraving on scrap wood and it burned uniformly all through the job.

Did have trouble first starting that pulse showed purple light on the tube but had no output to the first mirror. hooked up the digital ammeter to the PS and it was pushing 22mA … way too much… went into the ruida settings and dialed max current to 79% and pulse was generating 17mA and I was getting a good beam to all the mirrors.

setoff a job @ 70% power in lightburn as a small square cut and the system was pushing 22mA again and had no tube output. backed it down to 60% which somehow is 20mA and get a beam all the way to the bed…

new tube and power supply?

I was under the understanding that as tubes aged and leaked, they can take more amps to get the same output, and that a failing power supply was more than up to the task of killing one off. They seem to take eachother out, much like a car battery and a bad alternator.

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