Laser Machine Grounding/Earthing

[Want2build1]

To add to this ...

Recently my Laser PSU died.
So, I've had to read up on PSU wiring, inputs and outputs ...

The return wire from the tube is connected to the case/chassis !

so, if you get a bad earth connection in the mains supply or plug - either end- then the chassis is potentially at 25Kv .

Unlikely , you might think but ! ...

I just bought a K40 laser machine as a backup. This arrived with a dud tube. The fault was a cooling water leak INSIDE the tube ! which effectively shorted the 25Kv HT to the chassis !

Sooo .. I think the warning for the extra earth connection direct from machine to ground, is sort of a make do safety precaution, to cover this bad design 'feature' .

When I realised this, I had to wonder how the RCD didn't trip, with a constant 20mA or so leaking to earth. I came to the conclution that the flyback transformer produces an isolated current, so the RCD wont protect you.

It's kind of unbelievable that this is a designed situation, not a fault situation.

So .. check your earth connections everyone !

:)