Advice installing new parts (LPS & Tube)

So a while back I had some issues with my laser so I bought some new parts… quite a few
My laser was suffering from a loss of power and lots of help from @donkjr it was determined that it could be either an LPS or Tube issue so I have purchased both but was considering installing the LPS first to see if this resolves the issue.

After that I can install the tube, I also bought new mirrors, lens, cloudray head, new air assist pump & hoses.

My questions are (I have looked but could not find anything) but is there anything I need to know about installing the LPS and Tube? Is it just as simple as removing the old ones and connecting the same wires?
Or is this anything special I need to do or watch out for?


*also - joys of living in Australia is that it takes this long to get things delivered


Ensure that the anode connection is properly connected and sealed with silicon.
If you need more info on this let me know.

Ensure you have a good ground on the cathode side, either directly (if no meter) or on the other side of the meter if you have one.

An optical alignment will be necessary after tube replacement.


Thanks @donkjr, installed the LPS but did not resolve the issue so I am going to install the new tube I purchased as well.

I used the silicon that came with the laser but comes out like white milk, I have been looking for what type of silicon I should use but have had no joy.
Any suggestions on the best type of silicon to use?

Alternate silicon: Permatex Blue RTV Gasket Maker. Available in auto and big box hardware stores.


Got the silicon last night, I’m in home quarantine due to recent travel but my wife went and picked it up for me.

So today I removed the old tube and have started to install the new tube and encountered another roadblock (really not having much luck here), the tube is detached at the lens.
Is this something that can just be glued or is it best to get the tube replaced?

The part which came off is the cooling ring for the output mirror. The tube itself is most likely still perfectly fine.

That ring can be glued on (again), but you have to be careful to not get any glue anywhere else.

But there is of course a chance that this fails or that the tube is already dead for some other reason. I recommend to contact the seller first.


Yeah that’s what I figured, sent the supplier a message with a photo so hopefully they exchange it as gluing does not sound like the perfect solution.

I bought two tubes and the other was all good.

So have the second tube in and still need to realign but can happily report that my laser is working now

Huge thanks to @donkjr for all his advice


When you get any updates from the seller. Please let us know! This is the same issue I have. And it doesn’t seem like you can just put it back in place. The silicon tube is “too long” which is probably why it disconnected in the first place.
Also. New K40 owner here. So I am looking at everything to see how to start it up, fix any issues, waiting on parts to upgrade since every video I’ve seen so far says upgrade half the damn thing before doing much else besides start it up to make sure it works first.

Hi @Dice — if you haven’t already, see the “K40 Intro” at the top. That links to the whole #k40:intro category which might be helpful.


will let you know @Dice, they have emailed me back today to say they are checking with their supplier so not taking that as a great sign but will let you know.

Must add I am lucky it was the first tube I unpacked that was broken otherwise it would have just sat on my shelf until I was ready to use it

Where did you purchase the extra tubes as well?

I’m in Australia so I found a local supplier here that sells Vevor tubes

Thank you. I have the same situation posted by Trojan where the cooling ring is disconnected. And none of the videos show how to reconnect it. Any possible way? Or is it a bust and I need to purchase a whole new tub?

There was a long discussion on this on G+ but I cannot find that thread.

I know that some glued the jacket back on with high temp epoxy and some with high-quality CA.
I am not sure how well the repair worked but what do you have to lose in trying the repair?

I think a repair can work if the glue does not get on the output window. You can google this problem and there is evidence that others have successfully glued it back on. That is if the output mirror seal is not damaged and the gas has not leaked.

I have often thought that if I had to do this repair I would remove the tube and position it upright in some kind of holder so the cooling ring will sit flat and gravity is not helping the glue drip onto the output mirror while curing. I would apply a thin line of glue on the perimeter of the ring so there is no sqeeze out onto the mirror, then tape it flat on the top. The water jacket tube’s tension may make this difficult so I would dry assemble it first to verify that it can be held stationary with tape. I think I would use epoxy that is designed for glass.

This would be my choice:

Others have used a wedge to hold the glued ring in place while in the machine but I would be concerned that the glue would drip across the mirror from the top of the seam.

You could also apply CA, hold the ring in place and then spray the perimeter with CA accelerator. I am not sure if the accelerator would get on the mirror and contaminate it or how strong the joint would be.


One last question for now. Apologies if this is the wrong place to ask (forums are new to me). Safety glasses? Recommendations please.

The good news is that glass, acrylic, and polycarbonate are opaque at 10600nm CO2 primary laser wavelength.

I wear glasses, but also have wrap-around laser safety goggles. The ones I have are similar to (earlier version of) these:


Glasses are important but if you do not already have them add interlocks in the front and rear covers.


Are you saying to add limit switches so when the covers are opened it shuts off? I do have those on the way.

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Yes switches in the covers that interlock the LPS i.e keeps it from firing when covers open :slight_smile:

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