Introduction: How to Test and Set a Chinese (China) Made CO2 Laser Power Supply to Get Long Life From Your CO2 Laser Tube for Your Laser Engraving and Laser Cutting Machine System

Be safe when performing this project.


The high voltage laser power supply settings can greatly affect the lifetime of the CO2 glass laser tube.  A setting above 30 mA will, in almost all cases, greatly diminish the operational life (changing an expected life of several years to months).  Even though the laser tubes are ranked in months, such as the 60 watt tubes, I have had customers use them for years before they finally loose power.

More recently, the higher power CO2 glass laser tubes, above 80 watts, and certainly 100, 130, 150, and 180 watts have been more inclined to have shortened lives because the power supply is improperly set.  For example, I had an unscrupulous seller who sold me a 150 watt laser with a power supply set at 34 mA.  My Mahoney laser power probe measured 145 watts.  Then, I contacted the seller because my multimeter read 34 mA.  His engineer said the power supply should be set to 30 mA for full warranty on the tube.  After setting to 30 mA, I measured the laser output power and got 129 watts.  Then, I contacted the company and returned the laser because the seller had actually sold me a 130 watt laser with a 150 watt price tag.

Whatever your reason for checking the power supply current, the steps are provided to demonstrate a safe manner to take a reading then take action to remedy.

Step 1: Do Not Touch the Red Wire.

1. Power off laser machine
2. Wait ten minutes. this is the time for the power supply to drain power from its electrical capacitors. 
3. Setup as shown in photos below.  You will need to purchase and use two sets of wires.  We recommend a black wire with aligator clips on each end and a red wire with aligator clips on each end.  These wires should be available at radio shack.

          A. See the power supply wire connection.  Do not touch the red wire.  It has extremely high voltage that is lethal.

          B.  See the thin wire.  It is colored blue, or black, or green as shown.

Step 2: Insert Meter Wires to Measure Current (mA)

C. See the meter below as an example meter.  Some meters are slightly different, so adjust instructions as needed.  Set meter to read current at mA.  Set meter to read DC current.  Insert red cable of meter into meter connection for current (labeled mA, or micro A, or A).

Step 3: The Meter Reading Should Show the Proper Units (mA) and a Zero Value

Step 4: D. Disconnect Thin Wire (colored Blue or Black or Green) From the Laser.

Step 5: E. Connect Your Wire to the Laser (aligator Clip Is Useful on Return Wire).

Step 6: F. Connect Your New Wire to Meter Red Wire. Use an Electrical Insulator, Like the Wood Block Shown, to Support the Wire at the Connection.

Step 7: See the Solid Electrical Connection. See Its Location, in the Center of the Wood Insulator Plank.

Step 8: G. Connect the Thin Wire From the Power Supply (colored Blue/black/green) to the Black Wire of the Meter Using Your Wire (alligator Clips Are Useful).

Step 9: More Cable Connections Located in the Center of the Insulating Board

Step 10: Confirm Electrical Connections. Take Reading.

Check and confirm all connections and review these instructions.  After you confirm that all connections have been completed properly, then power on the laser machine. 

Using the touchpad, select Menu and set the laser power to 5% and the time to 3000 ms.  Power on the the laser from the touchpad and read the meter after the number settles.  To confirm that you have no problems, there will be no sparks or electrical arcing.  If sparks or electrical arcing then stop all work, power off the machine.

If the meter provides a reading and no sparks or arcing, then proceed by setting the laser power to 100%.

The current measurement at maximum output power should be 28 mA for a long life setting for a standard Chinese CO2 glass laser tube.  If the value is higher (such as more than 30 mA) then the internal gases will be consumed much more quickly during operation and the glass laser tube will need to be replaced more often.

Step 11: Adjusting the Potentiometer to Reduce Current

To adjust the current downward, consult your power supply manual.  DO NOT open the laser power supply enclosure and insert your fingers.  Using a grounding wire, ground everything when working on a power supply.  I was shocked six hours after power off, by touching the underside of the circuit card inside the laser power supply.  Always use a wire connected to ground to remove any lingering voltages stored in the capacitors inside the laser.  In many cases, the enclosure does not need to be opened and the potentiometer can be adjusted.