Crackling noise coming from laser power

[archieroques]

My cutter (a 7040 from China, Ruida controller) has just started making a crackling/arcing noise in the middle of a cut. It sounded like welding - sparks cracking, but quietly. Only occurs when the laser is on.

Does anyone know what this could indicate? I won’t have time to investigate for a week or so but any early heads-up would be appreciated.

edit: I’ve quickly checked the tube and all seems intact. The electronics hatch looks fine and smells sparky, but the cutter will need totally moving in order to make the hatch accessible so I can’t do a full look.

[Smokey]

Firstly a warning. There might be large amounts of static or discharge sitting about in your machine waiting for you to touch the wrong thing. If the machine is arching somewhere it’s also possible you’ll get a shock just touching the machine. Ensure your machine is properly earthed also.

It’s possible that there isn’t enough insulation around the anode/positive connection on your tube or that there is a place along that connector where the wire is exposed, though this would seem unlikely.

Another possibility is that your cathode/negative wire (at the blinding/shooty end of your tube) is not connected at all, either at the tube end or on the PSU and is arching to the case of the machine.

Yet another possibility is that your PSU is just horribly cheap and that’s the noise it makes when it is working. It might be worth noting the type of PSU you have and being prepared to replace it. If you have the laser cutter I think you have, the PSU is situated in the side bay at the back on the right, directly below the anode/positive end of your CO2 laser tube.

Let us know how you get on.

Dominic

[archieroques]

Pleased to report that I am still alive and it hasn’t electrocuted me yet! I can’t see any evidence or arcing, sparking or bare cable around either end of the tube or along the length of it, or near the power supply or on the wires. I would think that from the sound its making it would make some form of mark on something if it were arcing along the wire…

The only thing I can see is a slight discolouration on one of the power connectors (see picture) but that may have been there before. It looks a bit light it’s been subjected to high heat but then it could just be dirty.

I have a feeling it’s the power supply and would be happy to open it and check for skid marks but I don’t know how to short the contacts out beforehand and discharge it so I don’t get shocked and I’m not too keen on finding out the hard way.

I’m also not mighty keen on powering it up for a test whilst standing next to the open door, although I feel that might be the only option for seeing what’s wrong.

The tube doesn’t power up at all, so something’s definitely broken broken rather than just making a funny noise.

[archieroques]

I’ve also contacted the seller in the hope of a replacement power supply - even if it’s another rubbish one I’ll know what to replace.

[Smokey]

I’m pretty sure it’ll be your power supply… and maybe the tube as well. Contact me via twitter DM I have a solution.

Dominic

[Smokey]

Just to note, if the PSU is arching near plastics or has a damaged wire, you’d get very black melted areas like you’d set fire to the plastic with a lighter. The blackening you can see on your connector is just dust and dirt.
I’d not recommend opening up a PSU unless you really know what you are doing around transformers and big capacitors. Having the door open for a test shouldn’t be too risky. I’d recommend trying a new PSU first.

Dominic

[archieroques]

For reference… this is what was inside the failed power supply:

[idnorton]

Nasty!

Thanks for coming back with pictures to tell us what the fault was

Ian