Measure resistance from thermistors

Use this procedure to measure the resistance of each thermistor wire.

  1. Use a digital multimeter to measure the resistance from each thermistor wire, using these connector-pin locations:
    Thermistor location Location of thermistor wires/connector 1st connector pin 2nd connector pin
    Inductor 1A PCB 1 (plasma power supply) J1.4 pin 3 J1.4 pin 4
    Inductor 1B PCB 1 (plasma power supply) J1.4 pin 5 J1.4 pin 6
    Inductor 2A1 PCB 1 (plasma power supply) J1.4 pin 7 J1.4 pin 8
    Inductor 2B1 PCB 1 (plasma power supply) J1.2 pin 1 J1.2 pin 2
    Inductor 3A2 PCB 1 (plasma power supply) J1.2 pin 3 J1.2 pin 4
    Inductor 3B2 PCB 1 (plasma power supply) J1.2 pin 5 J1.2 pin 6
    Transformer 1 PCB 1 (plasma power supply) J1.4 pin 1 J1.4 pin 2
    Transformer 22 PCB 1 (plasma power supply) J1.25 pin 1 J1.25 pin 2
    Control transformer2 PCB 1 (plasma power supply) J1.25 pin 3 J1.25 pin 4
    Chopper 1 PCB 2 (plasma power supply) J2.2 pin 1 J2.2 pin 3
    Chopper 21 PCB 3 (plasma power supply) J3.2 pin 1 J3.2 pin 3
    Chopper 32 PCB 8 (plasma power supply) J4.2 pin 1 J4.2 pin 3
    Coolant temperature3 PCB 1 (plasma power supply) J1.2 pin 7 J1.2 pin 8
    Coolant temperature2 PCB 2 (cooler) J2.4 pin 1 J2.4 pin 2
    1 XPR300® and XPR460® only
    2 XPR460 only
    3 XPR170® and XPR300 only
  2. Look for a resistance value that is outside of the minimum or maximum value in Ohmic resistance values for thermistors.

    At approximately 25°C (77°F), look for a resistance of approximately 10,000 ohms (Ω).

    If you get this condition...Do these steps...
    The resistance is more than the maximum value. Speak to your cutting machine supplier or regional Hypertherm® Technical Service team. They can help you to identify if there is a wiring fault or if thermistor replacement is necessary.
    The resistance is at or near 0 ohms (Ω).
    1. Examine the wiring between each thermistor and its connector pins.
    2. Look for shorts between wires or to the ground.
    The resistance is in the permitted range. Continue cutting system operation.
    The resistance stays at less than the minimum ohmic value or does not change after the coolant gets to:
    • ≤ 85°C (185°F) for XPR170 and XPR300
    • ≤ 75°C (167°F) for XPR460
    		 Speak to your cutting machine supplier or regional Hypertherm Technical Service team.
    The thermistor resistance is in the permitted range when the thermistor is disconnected from the control Printed Circuit Board (PCB), and the code continues when the thermistor is reconnected to the control PCB. Speak to your cutting machine supplier or regional Hypertherm Technical Service team. They can help you make a decision on if control PCB replacement is necessary. Refer to Plasma power supply control PCB (141545) diagram.
  3. If you cannot find or correct the problem, speak to your cutting machine supplier or regional Hypertherm Technical Service team.