CO2 laser - fires 100% power no matter the program

Sun Mar 13, 2022

I hope you can help me.
I just now tried my first test after installing a new tube. First task is to scribe a light line to frame some stock. I programmed 20% power first, then 10%, then 1% just to see what would happen because I'm getting 100% power output no matter what power I program in Lightburn. I've set my minimum power to 1% just so it stays out of the way, and I've checked my vender machine settings and maximum and minimum power are at reasonable levels (99% and 10% respectively). But no matter what I send to the machine, once the laser fires, it's always at 100% (about 23W).

Any ideas where to start?

I'll add that I did tweak my power supply adjustment pot because it was capped at about 15W and I turned it until it would just reach 23W (because from what I could find, that's a relatively safe power for my 80W tube). I did have to unplug and re-plug the two green terminal plugs to the power supply (so I could access the pot through the hole), but I would think that if that went bad, it would either fire or fail, not just fire 100% all the time.
Other than that, the only mods I've done are the physical replacement of the tube.
I'm pretty new to Lightburn, so maybe there's another setting I'm missing? I'm assuming if you select a layer and set "maximum power" on the popup window for that layer, that's the power that should be firing in operation?

I'm a bit lost and don't know where to start down this troubleshooting path.

Sun Mar 13, 2022

Anybody home?
I guess I should describe that my controller is Ruida RDC6442G-B and my power supply is a ZYE MYJG 100W
(like this: https://www.cloudraylaser.com/products/ ... cd-display )

OK I don't know how, but it does indeed seem like probably something got jiggled or something while I had the power supply unmounted from the machine enclosure while I was trying to set the power output pot. It was working OK before but even if I set the maximum power output very low on the controller panel and do a pulse, it still puts out full watts. I have checked all the wiring and it all seems good.

Either I lost the PWM signal from the controller somehow (seems unlikely since I didn't mess with anything on it other than temporarily unplug the green terminal plug from the power supply), or while I was messing with the power supply, I somehow fried or shorted something fragile so the PWM is always 100% now.

I did use a ceramic screwdriver to adjust the pot, so I didn't short out anything with the tool, but maybe something else could have happened?

The power output pot seems to work fine as it does limit the output of the power supply (I have lowered and raised it a few times now and it responds predictably). But when I try to fire it from the controller, it's getting nothing but 100%.

Any ideas what I should try next? I have an oscilloscope but I'm kinda green on using it. But I could maybe verify that I'm getting a signal from the controller I guess. Could maybe draw up a test for maybe 5 short lines with varying power on each and see if the pulse width is changing.

Is there some kind of procedure I could do to check things out? I wish I knew more about this, but I guess I might after trying to work this out, whether successful or not.

It would be helpful to at least know what kind of signal the power supply is expecting so I can check whether the controller is outputting something appropriate.

Any help here would be appreciated, so thanks in advance for anything. I'm feeling a bit lost & overwhelmed. Just not sure what to do.
By the way, I do know not to connect my scope to the output that fires the tube, in case anybody got spooked there. I would expect the controller PWM is 5V or at least something that won't damage the scope... or me.

Mon Mar 14, 2022

In case it helps (I imagine it does):
I hooked up the scope to the outputs from the controller. It looks OK.
5.1V and changing to various percentages of PWM does indeed output the same PWM as measured by the scope.
The wires were a bit noisy so I added a ceramic cap between them and it filtered it out much nicely without dropping the voltage significantly. I thought maybe the noise might be faking a signal, but after cleaning it up it still does the same thing.

That got me thinking about the possibility that the PWM signal is basically being ignored by the power supply, so I disconnected that wire and pulsed it and, with the PWM wire disconnected, the power supply fired 100%. That must mean something?

Then I reconnected PWM and disconnected "enable" and it wouldn't fire, which is what I would expect, but there it is.

OK, so it doesn't look like a controller issue. I could replace the power supply, but before I do, any ideas? Maybe this thing is OK and I'm just too dumb to figure it out? That's very possible. I mean all I did was tweak the output pot with a ceramic screwdriver, but whatever. I wouldn't think this is a tube issue, but what do I know? It is a brand new tube, but would something like 100% power flow for some reason in a faulty tube?

Any advice is welcome. Thanks.

Mon Mar 14, 2022

One more test done, one more data point.
I wanted to see if some weirdness was going on with the new tube, so I tested it with a Mahoney gauge and it fires well over 80W (yeah, I need to limit that once things are running right). So it looks like the tube functions just fine.

Mon Mar 14, 2022

OK, just so ya know...
If this happens again, then I will just purchase a non-flaky power supply.

I simply removed the power supply and popped the top off. There was a small piece of what looked like plastic tumbling around inside, but nothing conductive.

I fiddled with the adjustment pot a bit and tested it with the top off. It worked! Hmmm. Carefully put it back in and tested again. It still works! however, the power was waay high, certainly not reflective of the small amount I turned the pot. I fiddled more with the pot until I got it to a place I can live with for now.

Then the big test - I drew up an array of small circles and put varying power on them. That worked too! So I guess I've poked and band-aided the thing to working, but time will tell if it's a long term thing. I have doubts, but we'll see.

Anyway, thanks fer nuthin'

But I'll leave this here in case it happens to somebody else.

My conclusion: good quality power supplies are worth the cost.

Sat Mar 26, 2022

Hello Vinito

If I understand correctly things are working correctly?

Years ago I serviced machinery and every once in awhile I would run into some flakey problems. One of the issues I ran into was bad and cracked solder joints on PC boards and typically at connectors. I had access to a microscope and that helped a lot, you would be surprised how tiny a bad solder joint can be.

By unplugging and plugging connectors you may have cracked a marginal solder joint. Maybe open up the HVPS unit and touch up the joints at the connectors with some “juicy lead solder” (Big Clive on YouTube).

Just my 2 cents.

Frank