Laser power supply unit for an OMTech CO2 laser

OMTech Laser Power Supply: How to Know It's Failing and What to Do About It

CO2 laser power supply problems usually show up as a sudden loss of cutting power that settings won't fix. To check, close the lid, press PULSE on the machine's control panel at about 25–45% power and watch the mA meter. Current stuck at zero, or not changing with the power setting, points to the power supply; current rising with no beam points to the tube.

The laser tube gets most of the attention when CO2 laser owners talk about consumables. The power supply is the quieter failure, but in some ways it's the more disruptive one, because it can go without much warning and its symptoms are easily mistaken for a tired tube.

We've run OMTech CO2 lasers in daily production since January 2023, and two of them since June 2024. The older machine has needed its power supply replaced more than once; each has lasted roughly 18 months to two years in commercial use. Here's what we've learned.

What the power supply actually does

The laser power supply converts mains electricity into the high-voltage DC the laser tube needs to fire: OMTech's current 80W supply is rated at up to 40 kV. Without it, nothing cuts. It also sets the tube current according to the power level your controller requests, which is why power supply problems often look like cutting problems.

How to tell it's the power supply and not the tube

This is the question that's easy to get wrong first. The symptoms overlap (the machine isn't cutting through, and power adjustments aren't helping), and the tube gets blamed because it's the more familiar consumable.

The pattern gives you a first clue:

Dying tube: usually a gradual fade. Cuts get weaker over days or weeks. You compensate by increasing power or slowing speed, it works for a while, then stops working again. A tube that glows white when it fires, or gives a split beam spot, needs replacing. A tube can also fail suddenly if it cracks or leaks.

Failing power supply: often more sudden. The machine is cutting normally one day and the next it isn't cutting through at all, even on materials and settings that worked fine yesterday, and changing power and speed makes no meaningful difference.

The pattern is only a clue, though. The mA meter tells you more.

How to test it safely

This is the method in OMTech's own troubleshooting guidance, and it doesn't involve opening the machine:

  1. Put a piece of scrap wood under the laser head, keep the lid closed, and have the machine set up as normal with the chiller or pump running.
  2. Set the power to about 25–45% and press PULSE on the machine's control panel, not in your software.
  3. Watch the current on the control panel's mA meter while it fires. Don't open the electronics compartment to read the power supply's own display while the machine is powered; if your machine has no panel meter, ask OMTech how to check the current on your model, or leave the test to a qualified person.

Reading the result:

  • Current rises but there's no beam, or a weak one: points to the tube.
  • Current stays at zero, stays flat, or doesn't change when you change the power setting: points to the power supply.

For reference, OMTech's guide gives normal readings for 50–80W cabinet lasers of about 6–8 mA at 25% power, 13–15 mA at 50% and 21–24 mA at 70%.

Don't use LightBurn's on-screen Fire button for this. LightBurn's own documentation says that button is for low-power focusing on diode lasers only, never CO2.

Many supplies, including OMTech's LN-80, also have a TEST button and a current display on the unit itself, and OMTech's troubleshooting guide says a PSU TEST reading under 10 mA (taken with the supply's green 6-pin control plug disconnected, as the guide describes) usually means the supply needs replacing. That button and display sit on the supply inside the high-voltage electronics compartment, and the TEST button fires the tube. Don't reach into that compartment while the machine is live: only use the TEST button by following OMTech's guide step by step, with the machine isolated as the guide describes, or leave it to a qualified person. For most owners, the control-panel test above tells you what you need.

Other signs worth noting: an indicator light on the supply that doesn't light or behaves abnormally on start-up, or arcing at the supply itself, both point to the power supply. Both are inside the electronics compartment, so the same high-voltage caution applies.

A high-voltage warning: the supply works at up to around 40 kV. Switch off and isolate the machine before opening any panel, and don't open the electronics compartment unless you know what you're doing: capacitors can hold a charge after the machine is switched off. If you have any doubt, ask a competent engineer rather than diagnosing blind. We can recommend a reliable freelance laser engineer if you need one (get in touch), but read the warranty note below first.

Check your warranty before you buy a replacement

OMTech UK's warranty page (checked October 2026) gives one year on tubes and power supplies for 70W-and-above machines, and two years on machine parts (some excluded), for machines bought direct from OMTech UK. The Turbo-758 product page still says six months on the tube and power supply, so confirm your terms. OMTech UK's warranty terms (checked October 2026) exclude faults caused by not using an OMTech-supplied water pump or chiller, and alterations or servicing by anyone OMTech hasn't authorised. If your machine is still under warranty, check with OMTech before swapping the chiller, pump or other parts. That includes fitting a supply yourself, buying a third-party one or calling in a freelance engineer: a supply that fails inside the warranty may be replaced for free.

Where to buy a replacement

Check the label on your own supply before you order anything, and match the wattage. OMTech UK's current 80W replacement is the LN-80 (LPS-N080-UK), rated for machines "80W or lower". The Turbo-758 is now sold as 90W, so confirm the right supply for your machine with OMTech before ordering; OMTech also lists a 100W supply.

We've paid around £150 for a replacement supply since 2023. For comparison, in October 2026 omtech.uk listed its 80W LN-80 at £99.59 and its 100W LN-100 at £127.19, with stock unclear when we checked, so check the current price and availability.

As with tubes, the OMTech website is the first stop but may show out of stock. Phone OMTech UK directly before looking elsewhere (contact details checked October 2026):

We've also had good results with Cloudray, who sell compatible supplies (including the common MYJG type) and have a UK warehouse. Their 80W supply is available on Amazon UK: see the Cloudray 80W laser power supply on Amazon. Check the wattage rating matches your machine before ordering, and buy from a seller with a clear return policy in case the replacement unit is faulty. It happens.

Replacing it yourself

A power supply swap is a wiring job, not a mechanical one. The supply sits in the machine's electronics compartment, held by a few screws. The connections are labelled and there aren't many of them. Photograph everything before you disconnect anything, and reconnect in reverse order.

Safety is not optional here. A laser power supply works at voltages that can kill. Always:

  • Switch the machine off at the wall, unplug it and make sure it can't be switched back on while you work.
  • Treat the supply, the high-voltage lead and the tube terminals as live. No manufacturer we know of publishes a safe waiting time, so don't rely on "wait a minute and it's safe".
  • Don't touch the large capacitors on the supply board.
  • Follow OMTech's YouTube tutorials and written guides step by step.

If you're not confident with electrical work, don't do this yourself. Paying a qualified engineer is considerably safer than a rushed DIY job on high-voltage equipment, and we can point you toward reliable help if you ask.

Prevention and planning

OMTech specifies its LN-80 supply at an MTBF (mean time between failures) of at least 30,000 hours, but that's a reliability statistic, not a lifespan, and in practice there's no clear service life the way there is for tubes. In hard commercial use (5 to 10 hours a day, five days a week) ours on the older machine have lasted roughly 18 months to two years before needing replacement. Our Turbo-758 is still on its original supply after daily use since June 2024. A hobby user running a few hours a week should expect considerably longer.

Once your machine is outside OMTech's power supply warranty, the most useful thing you can do is keep a spare to hand if you're running commercially. A dead power supply with no spare in stock means a machine standing idle, orders delayed and an urgent delivery charge on top of the part cost. Buy the spare when the machine is working, not when it isn't.

For the full picture on running costs and reliability across both our machines, read our OMTech reliability post. And if the test points to the tube instead, the UK laser tube buyer's guide covers sizes, sourcing, brands and fitting.

Not sure what you need?

Both machines are running at our OMTech showroom in Buckley, North Wales. Visits are free, informal and by appointment only: email info@cherrygrovecraft.co.uk with a couple of dates, and the full address comes with our confirmation. If you haven't bought a laser yet, our OMTech discount code Cherrygrovecraft saves you 4% at omtech.uk (checked October 2026).

Frequently asked questions

What are the signs of CO2 laser power supply problems?
A sudden loss of cutting power that changing settings doesn't fix, an mA meter that stays at zero or doesn't follow the power setting when you press PULSE, an indicator light on the supply that doesn't light properly, or arcing at the supply. A gradual fade over weeks is more often the tube.

How do I test a CO2 laser power supply?
With the lid closed, press PULSE on the machine's control panel at about 25–45% power and watch the mA meter: current rising with no beam points to the tube, while current stuck at zero or not changing with the power setting points to the power supply. OMTech's troubleshooting guide says a PSU TEST reading under 10 mA usually means the supply needs replacing. That TEST button is on the supply inside the high-voltage compartment, so follow OMTech's guide exactly or leave it to a qualified person.

How much does a replacement OMTech laser power supply cost?
In October 2026 omtech.uk listed its 80W LN-80 supply at £99.59 and its 100W LN-100 at £127.19, so check the current price and stock. We've paid around £150 for a replacement supply since 2023.

Can I change a laser power supply myself?
It's a wiring job with a few labelled connections, but the supply works at up to around 40 kV and its capacitors can hold a charge after switch-off. If your machine is still under OMTech's warranty, contact OMTech first, because servicing by anyone other than an authorised representative is excluded; if you're not confident with high-voltage work, use a qualified engineer.

How long does a CO2 laser power supply last?
OMTech specifies its LN-80 supply at an MTBF of at least 30,000 hours, but that's a reliability statistic, not a lifespan. On our older OMTech, working 25 to 50 hours a week, each supply has lasted roughly 18 months to two years.

Disclosure: some links on this page are affiliate links, and we earn a commission from OMTech on purchases made with our code or link. It costs you nothing extra.

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