Hi All,
I’ve bought a second hand 50W vevor laser.
The tube colour looks good but no output with a test fire of 24mA.
I’ve cleaned the lens at the end of the tube. Placing a piece of paper before the first mirror and no marking at all.
Ideas?
Have you tried using a mirror to see what the lens mirror in the tube looks like?
If you get a 24mA reading on the ammeter and no beam comes out of the tube, there is a high risk that it is damaged.
…is there water in the tube??, looks so clear…
mmmm, that looks very nice…
How do you read the mA? Is there a physical ammeter on the machine?
I put a DMM in series.
when you measure 24mA by pressing the test button, as long as you press and your tube looks clean and neat…the safety switches are locked (…or you won’t be able to shoot…) - I don’t know, maybe I’ll find out how the power supply is, even if you get a reading on your measuring instrument.
I’m not sure how to measure the tube supply eg voltage under load.
I’m not planning on frying myself or the DMM.
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No, it’s dangerous and should only be done by people who know how it works, I’m not one of them either 
But there are so many smart electricians in our forum, I’m sure there will be some smart suggestions for you.
Is it a new machine?, looks new…
Are the pictures from your new machine or from your K40?
I also owned a K40 and loved that machine, I modified it quite a bit but the bed size was way too small in the end.
There’s no simple way, I have an hv meter on mine, but I don’t think it will tell you much. I have an 800 M/ohm series resistor to lower it down to 50uA.
You need to measure the tubes length to ensure you have a 50W tube, it needs to be 1000mm in length. If it’s a K40 type, these are usually between 650mm and ~700mm, which relates to less than 30W. You should limit the current around 20mA or less. Mine is a 45W (880mm) and I limit current to 20mA.
If the tube is glowing (such as in the picture) I’d think it would be lasing. If there is no output, that falls on the tube as the HV has to be there for the tube to lase (create the visual emissions) and draw current. There should be some kind of output at the end of the tube.
What is the open tube in the photo? I’ve never seen one of these with an opening like that.
Good luck
You look into a mirror.
Looks like it’s jammed over a glass tube next to the cathode terminal and filled with silicone caulk. Could that be the port where the gas inlet / vacuum pump was attached during manufacturing?
That port on my laser is on the anode end, but there’s a time for every style.
If that’s what it is, I betcha it cracked and the glop covers the evidence.
Which would explain why the tube doesn’t lase …