DGHUNST 40W CO2 Laser Power Supply (Model A)

Most K40-class supplies group their connections the same way, even when the labels and plug styles change. Expect these groups:

The labels vary between makers, so trust your photos over any chart. Label every wire with tape before you unscrew it, and note which plug each group used.

• If your old supply has the same plug positions, the swap is mostly plug-and-screw.
• If one group moves, you re-terminate those wires; that is an hour of careful work, not a disaster.
• If the high-voltage lead exits differently, check that it still reaches the tube without a splice.

A spliced high-voltage lead is where K40s start arcing. Run the new lead in one piece to the tube, and see the K40 tube and supply pinout notes for how the stock wiring is laid out.

1. Switch off the machine, unplug it from the wall, and keep the plug where you can see it.
2. Wait several minutes for the supply's capacitors to bleed down. Longer is better.
3. Clip a ground lead to bare chassis metal, fix the other end to a screwdriver with an insulated handle, and touch the tip to the tube's high-voltage terminal.
4. Only then touch wiring, and use one hand where you can.

DGHUNST separates the input and output sides completely and fits a grounded case. Both help, but neither replaces a real earth: the FG terminal must reach the mains ground, and the K40's frame must share it. Many stock K40s arrive with a weak ground path, so test yours with a meter before the new supply goes in.

Think about where the supply sits, too. It is air-cooled, so leave the vents clear and keep the high-voltage lead away from sheet-metal edges that could chafe the insulation. Go through the K40 safety basics again if the machine is new to you.

Tube life depends on current more than anything else. Most 40W tube makers put the ceiling somewhere around 15 to 18 mA; check your tube's own sheet and stay under it. A supply that can deliver more is a supply that can shorten a tube quickly.

• Keep an analog mA meter in the return lead. This supply has no display, so the meter is your only honest reading.
• Set a maximum in software or on the power pot, and mark it on the panel.
• Run test cuts at lower current first; many jobs need far less than the ceiling.

DGHUNST notes that the supply can run open-circuit for a short time without damage. Read that as protection against a fault, such as a loose high-voltage connection, not as a feature to lean on. An open circuit at high voltage means arcing somewhere, and arcing chars insulation and can start a fire.

Watch for the signs of a supply on its way out: a loud crackle or hiss from the case, a burning smell, or a tube that fires weakly while the meter reads normal. The last one can also be a tired tube, so rule out alignment and dirty optics with the mirror and focus checks before you buy parts.

After the swap, bring it up gently. Start the water, close the lid, set the power pot low and tap the test button once. Watch the meter, listen for crackling, then step the current up in small moves. If the reading jumps or the case hisses, shut down and recheck the high-voltage run.

Compare it with the supplies that do state more:

• FONLAND MYJG-40W. Marked 110V/220V and built for K40 machines, with screw-terminal and wire-lead connections. Choose it if you want the voltage settled on paper. See the FONLAND supply.
• OMTech MYJG-60. A 60W supply with an LCD current readout and 40W–60W tube range. Choose it if you plan a bigger tube later, and measure the bay first. See the OMTech supply.
• BAISULI Model A. Same layout letter, with a 110V version named. See the BAISULI supply.

Run this short list against the DGHUNST first:

1. Get the input voltage in writing: 110V for US mains, 220V for most of Europe and Asia. A wrong-voltage supply can fail on first power-up.
2. Match the Model A terminal photos to your old supply.
3. Measure the bay: the case is 6.89 x 5.71 x 3.15 inches.
4. Confirm your tube is 40W or less.

If all four check out, it is a sensible, no-frills replacement. Order a spare fuse of the correct rating at the same time; a supply swap is when a blown one turns up. Weigh a supply swap against optics and air assist with the wider K40 upgrade order.