I have a brand new Gweike LC6090 laser cutter with 80W RECI laser tube and Ruida RDC6442 controller. There is an ammeter mounted above the controller.
According to RECI the maximum current draw for the 80W tube is 24mA. When running a job set at 90% power, run straight from Lightburn, the Ruida display says the maximum power is 80%, and the ammeter reads 32mA, not the maximum safe 24mA.
Please can someone explain what is going on here? Gweike have set me up with a DingTalk support group. The one chap says not to worry about the current draw. They also say there should be a knob mounted underneath the ammeter to adjust the current, but there is not. There is also no obvious power adjustment on the laser power supply.
How do I adjust the power down so that I can use the full percentage range in Lightburn but not exceed the 24mA?
As far as I know, it can only be adjusted in the power supply itself. Most have a small hole with access to a potentiometer.
Btw. if the manufacturer recommends 24 mA I will also stick to that.
You can limit max power in LB but it is only a “stop” and not a rescaling.
The knob varies the tube current from 0% up to whatever the controller’s PWM output specifies.
As @bernd.dk notes, the high voltage power supply will have a small round hole giving access to an internal trimpot setting the maximum output current. The small blue trimpot at the lower right of the PCB is the one:
The hole is usually in an inconvenient (sometimes invisible) position when the power supply is mounted inside the laser. In my machine, that side of the supply faces down with a few inches of clearance.
Assuming you can get a small screwdriver in there, the adjustment is straightforward:
Set the controller for a 50% power manual pulse
Power with Min/Max button
Duration with Z/U button → Laser Set → Continue
Note the current on the meter during the pulse
Maximum current = 2 × that value
For your machine, adjust the trimpot so the current is 12 mA = ½ × 24 mA
This is my power supply, a ZYE laser myjg100W-Y. 100W in the description but the specs say it is suitable for 80-120W. I found the manual online, it says nothing about adjusting the power. There’s a little hole next to the ‘laser’ label at front left. Changing the phrasing of my Google search yielded an AI-generated result that indicated that on some models of this power supply there is indeed a hole labelled ‘laser’ that is the adjustment point. I will give it a go. The goal is to have long life from the tube but to also have a linear output from different power settings in Lightburn for accurate cutting and etching / engraving.
Small note, if you have the possibility to open the box - do it. If not, you have to fumble your way to the small pot and there is a risk that you short something - use a ceramic screwdriver.
And to make it even more interesting , some power supplies with internal mA meter have their pot on the side and not at the mentioned hole in the shown position next to the green sockets.
The unmarked hole you want is on the right side of the case (as shown in your picture) and likely inaccessible due to the wiring raceway (or whatever) a few inches further right.
Of course, trusting randos found on the Interwebs is also risky, but …
, some power supplies with internal mA meter have their pot on the side and not at the mentioned hole in the shown position next to the green sockets.
