Best K40s
BUCNYKKHV 40W Laser Power Supply
K40 replacement power supply · 40W

BUCNYKKHV K40 40W CO2 Laser Power Supply

A bare-bones K40 40W replacement supply with no published input voltage or layout. Buy it only after you have proven the old supply is dead and confirmed it matches your mains.

  • SeriesK40
  • Output40W
  • TubeCO2 laser tube
  • Input voltageNot published
  • Terminal layoutNot published
Right for
  • K40 owners who have traced a no-fire fault to the supply
  • Machines with a stock 40W tube
  • Owners able to match terminals from photos
Wrong for
  • Anyone who has not ruled out interlocks and optics
  • Buyers who need a stated voltage before ordering
  • Tubes above 40W
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Prove the supply is dead before you order one

A K40 that stops firing tempts you to buy a supply first and think later. Half the time the supply is fine. Spend twenty minutes on the checks below and you may save the cost of a part you did not need.

SymptomCheck firstSupply suspect when
No fire, mA meter at zeroWater-protect switch, lid switch, emergency stop, laser-enable buttonAll interlocks closed, water flowing, still nothing on test-fire
Fires weakly, normal currentMirror alignment, dirty lens or mirrors, focus heightRarely the supply; look at optics and tube age
Crackling or hissingHigh-voltage lead routing and the tube anode jointNoise comes from inside the supply case
Burning smell from the bayWiring insulation, loose terminalsSmell is at the supply and it has stopped working
Fuse blows at switch-onMains wiring, fuse ratingA new correct fuse blows again immediately

Work through the no-fire checks in order:

  1. Confirm water moves through the tube and the flow switch, if fitted, is closed.
  2. Check the lid switch and emergency stop, and the laser-enable button on the panel.
  3. Close the lid, wear 10,600nm glasses, set low power and press test-fire. Watch the meter.

A tube can also fail while the supply is healthy: a crack in the glass, a leak into the water jacket, or a discharge glow that flickers or changes colour are tube signs. A tube that has sat unused for a long time can also lose power. The K40 tube and supply guide goes deeper on telling the two apart, and the alignment checks rule out optics.

Specs

Measurements & ratings

SpecValue
BrandBUCNYKKHV
ModelBUCNYKKHV
SeriesK40
Output power40W
Laser typeCO2 glass tube
UseLaser tube engraving and cutting machines
FitsK40 machines with a 40W tube
Items1 supply
Input voltageNot published; confirm 110V or 220V
Terminal layoutNot published; match from photos
DisplayNot published
Case dimensionsNot published

Pin down the input voltage BUCNYKKHV leaves blank

BUCNYKKHV describes this unit as a K40 40W CO2 supply and publishes nothing else. There is no input voltage, no layout letter, no case size. The voltage is the one you cannot skip.

K40s run on the mains they were built for. US and Canadian machines use about 110–120V; European, UK, Australian and most Asian machines use about 220–240V. A supply built for 110V and fed 220V can fail at the first switch-on. The reverse usually gives a laser that will not fire properly.

  • Ask BUCNYKKHV which voltage the unit is built for, and get the answer in writing.
  • Check the case label as soon as it arrives, before any wire goes in.
  • Look for a voltage selector, and set it and photograph it if there is one.
  • Compare with your K40's own mains label; the supply should match the machine.

Ask for a clear photo of the front panel at the same time. That photo answers the layout question: whether the mains, control, DC output and high-voltage connections sit where your old supply has them. If the layout differs, you can still fit it, but plan on re-terminating wires by function rather than plugging them straight across.

If you cannot get the input voltage confirmed, do not power the supply up to find out. Choose a supply that states it, such as the FONLAND MYJG-40W marked 110V/220V or the BAISULI 110V version.

Measure your electronics bay too. With no published dimensions, the mounting holes may not line up, and new holes in the bay floor are part of the job.

In the catalogue

Where it slots in

K40 laser models by type, September 2026. Highlighted: BUCNYKKHV 40W Laser Power Supply.

Pull the old supply without meeting its stored charge

Even a dead K40 supply can hold a charge. Its capacitors and the high-voltage lead to the tube store energy after the plug comes out. Removal is where people get hurt, because the part is broken and it feels safe.

  1. Switch off and unplug the machine at the wall. Keep the plug in view.
  2. Wait several minutes before opening the electronics bay.
  3. Clip a ground lead to bare chassis metal and to an insulated screwdriver. Touch the tip to the tube's high-voltage terminal to drain it.
  4. Photograph the terminals, then label each wire with the name printed beside it.
  5. Disconnect the high-voltage lead at the tube end last, keeping its insulation intact.
The high-voltage lead carries enough to arc through air and through you. Never open the supply case, never work with mains connected, and never test-fire with terminals exposed.

Fitting the BUCNYKKHV runs in reverse: mount it solidly, land mains and FG earth, then control wires, then the 24V and 5V outputs, and route the new high-voltage lead to the tube anode in one piece. Keep that lead clear of sheet-metal edges; arcing starts where insulation rubs.

Check the earth before closing up. The supply's FG terminal goes to mains ground, and the K40 frame must share it. Meter from the frame to the plug's earth pin with everything unplugged. The K40 safety basics cover this with eye protection and ventilation.

Also consider

Worth comparing

3 Cloudray 40W CO2 Laser Tube
When the tube is the fault Cloudray 40W CO2 Laser Tube
Cloudray's 40W 720mm tube arrives with its high-voltage end pre-connected.
  • Replacement CO2 laser tube
  • 40W · 720mm long
  • Fits K40-size CO2 lasers
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Weigh BUCNYKKHV against the fully specified supplies

Every 40W supply here does the same job in a K40. The difference is how much each maker tells you before you buy. BUCNYKKHV tells you the least, which puts all the confirming on you.

  • FONLAND MYJG-40W: 110V/220V, screw terminals, convection cooling, published size. See the FONLAND supply.
  • BAISULI Model A: a named 110V version and a stated layout letter. See the BAISULI supply.
  • OMTech MYJG-60: a larger 60W unit with an LCD for current and water status. See the OMTech supply.
  • LYZYSNEJ K40 supply: similarly sparse, but at least marked 110V/220V. See the LYZYSNEJ supply.

Choose the BUCNYKKHV when three things are true: the diagnosis points at the supply, the voltage is confirmed for your mains, and the front-panel photo matches your old unit. If any of those is missing, one of the documented options costs you less time.

After the swap, set a current limit.

Take the maximum from the tube's own documentation, not from the supply; 40W tubes are commonly rated somewhere between 15 and 18 mA. Keep an analog mA meter in the return lead, since no display is described on this supply. Then step current up from low on the first test fires and listen for crackling. Once the machine runs again, work down the K40 upgrade order for the fixes that pay back first.

Keep the old supply in a box, labelled. It is your wiring reference if anything goes wrong, and a repair shop can sometimes tell you why it failed. That answer helps you avoid killing the new one the same way, whether through a bad earth, a chafed lead or a tube run too hard.

Shop talk

Fit & install questions

Is the BUCNYKKHV supply 110V or 220V?

BUCNYKKHV does not publish the input voltage. Confirm it in writing before ordering, and check the case label on arrival.

How do I know my K40 supply is dead?

Rule out the water-protect switch, lid switch, emergency stop and laser-enable button first. If test-fire gives zero current with all of them closed and water flowing, the supply is the likely fault.

Will it plug straight into my K40?

The terminal layout is not published. Compare a photo of its front panel with your old supply before you buy.

Can a dead supply still shock me?

Yes. Unplug, wait several minutes, and discharge the tube's high-voltage terminal to chassis ground with an insulated tool before touching wiring.