7. Make sure that each heat-exchanger fan has no visible obstruction, dust, or debris.
□
Use compressed air to clean this area, if necessary. Use personal protective equipment for
protection from airborne particulates and debris.
□
Make sure to keep fan rotation to a minimum during compressed air use. You can use a gloved
hand to hold a fan in position, if necessary.
□
Also make sure to fully install the panels on the cooler. When there are no side panels, there is
no air flow across the heat exchanger, which prevents the system from becoming cool.
8. Measure the resistance for the thermistor:
a. To measure the resistance for a chopper thermistor, disconnect the connector for that chopper
in the plasma power supply.
b. To measure the resistance for the coolant thermistor, remove the coolant thermistor wires from
the connector in the cooler.
Doing these steps makes it easier to measure only the resistance for the thermistors.
c. Use a digital multimeter to measure the resistance from each thermistor wire, using these
diagnostic codes and connector-pin locations:
Diagnostic code
Thermistor location Location of thermis-
tor wires / connector
Pins
560, 667, 678 Chopper 1
(cold plate)
PCB 2 (plasma power supply) J9 pin 1 J9 pin 2
561, 668, 679 Chopper 2 (cold
plate) (XPR300
and XPR460 only)
PCB 3 (plasma power supply) J9 pin 1 J9 pin 2
562, 669, 680 Chopper 3 (cold
plate) (XPR460 only)
PCB 8 (plasma power supply) J9 pin 1 J9 pin 2
587, 670, 681 Heat exchanger PCB 2 (cooler) J2.4
pin 1
J2.4
pin 2
d. Look for a resistance value that is outside of the minimum or maximum values in Ohmic
resistance values for thermistors on page 334.
At approximately 25°C (77°F), look for a resistance of approximately 10,000 ohms (Ω).
85 750 1250
95 600 1000
105 400 800
Diagnostics and Troubleshooting
8
333811530Instruction ManualXPR460
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