K40 not working

[calley]

Had some issues with my laser the last time I used it. It etched a small design ok, but it was missing some spots... and would crackle occasionally... I had to run it twice to get a complete job.

This time it doesn't seem to output anything. I'm hitting the test button... the power meter is showing 10ma like its supposed to and the tube is glowing like a dim neon sign. Its not crackling this time, but its not heating up anything in its path either... not even slightly.

Any recommendations on how to troubleshoot?

[Techgraphix]

Place a small piece of wood somewhere in front of your lasertube.. see if it catches fire..
If not.. Your tube is gone, most likely
If so.. Check the beams alignment.. probably your beam is obstructed somewhere. Even your nozzle can be (partialy) clogged by the debris coming from your workpiece..
Kees

[calley]

Yeah, I had tried that... Right out of the tube to be sure, but it didn't even get warm.

How can I tell if its the tube or the power supply? With the crackling, I was worried it was the power supply.

[Techgraphix]

Can you hear where the cracking comes from or even see sparks?
You might inspect the HV connector for burnt traces. And if you dare, open the HV supply and inspect that. Polluted dust inside is known to conduct highvoltages. It can also be that one of the more heavy components or components that become hot will come loose from the PCB.. Check the solderings.
BUT!!! be aware of charged capacitors!! first measure if they are depleted before you touch anything.. It can kill you !! And pull the mains-plug when you start working in the machine..
There is a way to load the HV-supply with a big resistor but what the value for this resistor should be depends on your supply.. I don't know.
Do you read any current when the laser should be active?
Kees

[calley]

The meter is showing 10ma... and at that level, it should be making something smoke.

The arcing sounds like it's coming from inside near the power supply, but I can't see it... and it isn't happening very often so its hard to say. I may pull it out and set it up on my bench so I can see what's going on.

Previously, the arcing was happening on the reflector end of the tube... my cooling tank was getting too cold and moisture was condensing on the tube. It's been awhile since I fixed that. Its definitely not happening in the tube hatch this time.

[Techgraphix]

10mA should make some smoke indeed.. I think you have to replace the tube. AND inspect the HV-supply..

Kees

[Tech_Marco]

Did you fix the laser tube by any chance? I saw that there was excess glue applied on it. So, I am guessing that the front cooling part fell off before and you're trying to fix it, am I right?

I agreed with Kees that the tube should be gone.


Marco

[calley]

No, the excess glue was factory original. No trouble on that end... though the cooling part on the total reflector end fell off at one point and I had to reglue it, but its worked fine for the last year or so.

Starting to sound like I just need to order a new tube. Though I'm going to test the power supply some time this week just to be sure.

[Techgraphix]

And: a dead tube is not worthless!.. There are quite a few people that collect tubes (industrial/transmitter/audio) that really want such a lasertube in their collection and pay you $25 for it.. a second live for the tube...

Kees

[calley]

So, did some testing tonight. The arcing is from the chassis to the red wire where it attaches to the reflector end electrode.

According to some forums, the tube becomes less conductive when it goes bad... and that causes the arcing.

I guess I'm buying a new tube

[Tech_Marco]

If so, you better to swap a new tube quick because the longer the arcing is happening, the higher chance that the LPSU is dying due to the uncontrollable current output from the arcing. It is similar to "short circuit".

Marco