I am trying to help a local community workshop/makerspace with their CO2 laser cutter after they replaced the tube (Ruida W2). The laser appears to fire, but with low and fluctuating power, and there is a buzzing noise. I think the buzzing noise is coming from the tube and not from the power supply/electronics bay.
I suspect there is an issue with the anode connection, but I am a little bit beyond my expertise here so am hoping for advice before I go to far into disassembling and rewiring the work previously done.
If anyone can offer advice for troubleshooting this it would be very helpful and appreciated! I am not sure if I should focus on the wiring, the power supply, the laser tube, or something else.
Forgot to add some details to the first post - the machine is “HL-Yeah” brand with RDC6445S controller and Reci W2 tube (date of production on the tube is 2025-11-16).
If the multimeter lead to the machine ground happens to slip off, the meter will immediately jump to about 20 kV until something arcs to ground. If that happens to be the keyboard underneath the meter, it will die. If that happens to be you, you will be recommending your better points to your maker.
If you must use a multimeter, put it inside the machine with the leads firmly attached and stay away from it.
With that out of the way …
The meter appears to be set for AC milliamps, which is incorrect for measuring the tube current. Set it for DC milliamps with a fixed range over about 30 mA.
However, an Old School analog meter is better than a digital meter, because the tube current has a truly bizarre waveform that the analog meter basically filters out. Fancy digital meters show essentially random values, particularly for power settings under about 30% of the tube’s maximum rating.
Because that is the high voltage wire, do not use DIY insulation. The power supply anode connection must be firmly attached to one end of a high voltage connector and the tube anode wire should be firmly attached to the end side. If there are any intermediate connections, replace them with a single run of HV-rated wire from the tube to the HV supply connector.
If the anode wire is arcing to the machine frame, the arc will have charred the insulation and you must replace that part of the wiring with a complete run of new HV wire. DIY insulation repairs will not work with high voltage wiring.
The cathode wire is (generally, see below *) at a low voltage unless it becomes disconnected from ground, at which point high-voltage hilarity ensues. The cathode wire in my machine had a loosely twisted-and-taped joint that I replaced with a crimped connector.
Some previous discussions may be helpful:
(*) Very high-power laser tubes may have both a positive HV connection to the anode and a negative HV connection to the cathode. If that is the case for your machine, the cathode wire will have chunky high-voltage insulation just like the anode and that multimeter’s wiring can kill you stone cold dead.
Thanks for pointing this out - good eye - I had missed that I had the meter set incorrectly in that video, so obviously that measurement was completely invalid.
Stick a 30mA mechanical meter in circuit. Most meters read RMS voltage so it’s dependent on the waveform the meter sees, but mos of this is digital and depending on how the machine is wired up the readings could give you misleading results.
Most of us prefer a mechanical analog mA meter over a digital one. These are standard meters, left is a 30mA and right is a 50uA meter for voltage.
On my machine the ground return for the cathode is a small black wire, only the anode has a lot of insulation. The area circled in green shows the anode (red) and cathode (black) wires, only the anode has a thick coating of insulation. I get the white connectors from Amazon and use these exclusively for HV connections.
I’ve been around these hobby lasers for almost 7 years, don’t know anyone whose dead or blind. It can’t be a good experience either way.
If you know of anyone dead or blind, please let me know so I can research it. I’ve been across 15kV and I know others that got across a hv Klystron tube for generating microwave, that’s 30kV, I don’t know anyone that’s died from it. Either way you need to have respect for high voltage in any case.
In any case, in the USA over 80% of the electrocutions deaths are by your home 120V service.
It’s hard to tell if the issue is the tube or the laser power supply (lps). I’d contact the tube manufacturer and let them advise you.
