This article is just the findings and results we found on several PSU´s but we cannot yet explain why or how this happens.
Are you a electric engineer or have knowledge about the workings of the PSU and able to explain this phenomena in greater detail? comment below or contact me trough email – thanks!

The power supplys in our beloved K40 machines are poorly built, the power in them is barely enough for running the machine itself.

I have been following a lot of user lately which machines just stopped working or had other electrical problems and they all have one issue in common, the PSU.
Upgrading the PSU before use will stop the PSU problems if the tube goes bad or the rectifier burns to prevent damaging the flyback.
The upgrade is a couple of dollars worth, but can save you a lot of waiting and head ache later.

See this article how to find if it is your rectifier or flyback creating the problems – if your machine already have problems.

Mainly there is two reasons why the PSU fails and they all have a source in the same components.

1: Tube failure

When the tube fails the PSU tries to energize the tube and fails and either starts arcing internally or on the positive lead on the tube.
This often destroys or weakens the flyback transformer, it does not like the arcing and with time it will probably go bad.
To this date i have 13 reports of user experiencing arcing a while before the PSU died completely after a dead tube.

2: Rectifier or Flyback failure

The rectifier used in the power supplies are the wrong specs, the power created inside the machine is upwards to 2-3A and the rectifier is a 1A model.
When this goes out it often damages the flyback (high voltage transformer) and with time it will stop working properly.

Heat problems
Some PSU´s do not have a fan, some have one. The problem is if you run it for long the small chamber will heat up quickly and the PSU will try to cool itself with the heated air inside the chamber.
To sleep better, add a fan on the back pulling air out of the smaller chamber, or put your PSU to the wall breathing from outside the chamber. See this article about tilting your PSU.

Grounding issues
Make sure all grounds inside the machine is 100% good, remove the ground bolt in the back and remove paint so the ground has good connection into metal.
Remove the blue tape on the PSU and add a extra ground wire from the bolt holding the PSU to the case from the GND bolt in the back.
Double check the ground wires to the controller and panel too.

How to upgrade your power supply before use

The best idea is to change out the bridge rectifier the first thing you do. You need to solder it, very easy hole trough mount so a simple soldering iron will do the job.

Parts needed
RS507, 700V, 5A bridge rectifier – | Aliexpress | Ebay
(you can use 1000V, 6A or similar too, just keep it above 500v and 4A)

Step by step
1: Make sure the PSU is not connected to the wall outlet. If it is, remove the cable and wait 24h before you do anything. The caps can store a lot of power for hours.

2: Remove the cover from the PSU and unscrew the board from the bottom.
Take some pictures to remember what goes where if needed.

3: Turn the board upside down and de-solder the rectifier. Clean up the holes with some “solder wick” or similar. Solder the new one in place. Clean up the soldering job with some alcohol.

4: Mount everything back in reverse order.

In this picture the flyback is marked in a red circle, and the location of the bridge rectifier is located inside the green circle.

hvt flyback rectifier

Time for a new set of optics for your laser machine? Lens & mirror kits starting at €49
Quick delivery in EU with stock in Sweden!
Check out Hawklaser spare & upgrade part store here!
Notify of
Inline Feedbacks
View all comments

Hi, I am having some issues after upgrading the psu with the HYT50.

Basically the laser beam is weak and, strangely, The cut is not fluid, a sort off dashed line. I never run over 35% power. 

ps I’ve upgraded psu because the the laser stopped cutting properly and I tought it was a problem with the psu. What could be? Thank you in advance.

ColMax Pickups

Hi … K40 update power supply … I bought the one you suggested … I have two questions … how to connect the new one … and can I use the old one for extra power that is not on the new one


My k40 will respond to files and follows the path but no laser firing. test switch on the power source will not make it fire. Rectifier is GBU610 so I should be good there. I suspect the tube or flyback transformer. The new flyback from Ebay is marked as ZY-08-40JS9. The transformer I have is marked as ZY-08-40JS9N. Will the flyback from:

work on my unit despite not having the N at the end of the number? It looks the same wireing and all, just doesn’t have the N. The machine is only a couple days old,lol.

Also could be the tube , but not sure. Will this tube work with my machine:

Your site had mentioned I should just upgrade to the HY-T50 or was it HS-T50, either way I can find out, but if I upgrade to the T50 can I still use the 40w tube or do I need to still buy a new tube for the T50….assuming it will be a 50w tube?


Iron Wolfe

Hello, I’ve been watching your work for a while trying to figure out how to fix my DOA K40.

I’ve seen many diagrams of the upgraded wiring for the HY-T50, but nothing explains how to go from a type 1 PS to the HY-T50. I bought the upgraded PS 2 years ago but couldnt figure out the rewiring since the t50 has less connections than the original. It’s recommended to have a 24v secondary PS for the controller and steppers. Am I just doubling up more wires on the fewer connectors of the T50, or eliminating some altogether?

Iron Wolfe

So I need a 24v power supply still. Got it, thanks!

Jacobo G.

Greetings! Thanks again for a great article!
Can you help me with something? We have a 150W CO2 cutter in the lab, the people before me stated that sometimes it started making squeaking noises from the PSU, months into use without any noise and then it started again but worse, I could see the arcing coming from the first flyback cable to the case with a loud noise and it stopped working and cutting completely. I put some high voltage liquid silicone around all the cables but apparently it wasn’t enough to stop that. We are thinking about changing the whole PSU but, could I just buy some 150W flybacks and replace the first with a new one? It would be a lot cheaper that way. Or is the real problem somewhere?, I’ll check for the kind of rectifier it has and replace it too, but will this be worth it, or should I just order a new PSU?

Thanks in advance for any help!

Keith Medford

Would love to get a 24v for the Controller board section. In the process of upgrading to a MINI GERBIL, and a larger area in the same case. Now the PS appear s to crapped out on me. Funny part ,is it works fine when impress the reset button on it, as long as it stays pressed that is. Any recommendations.

Andy Southam

I ordered a 10A 24V power supply to drive accessories (pointers, lights, air, etc) which aren’t going to even come close to using 10 amps. Would it be a good idea to change things so the stepper motors draw from this new power supply instead of what came in my stock K40?


I went to upgrade the rectifier in my new K40, having read this article. When I opened the PSU, I found a GBU 610 rectifier was installed, which is a 1000V 6A rectifier.

It maybe that the manufacturers have read this, and newer boards come with an uprated rectifier.