ESAB PCM-875A Installation, Operation And Maintenance Manual page 89

SECTION 6
Fault light activates (continued)
PCM-875A Plasmarc System
·
Over Temperature. The fault light will be mostly off
but will blink on for 1/10 of a second, every second.
This generally indicates that the duty cycle has been
exceeded. Allow the power source to cool before
returning to operate.
§
Thermal switch may be open. It will open if the
temperature at the IGBT base reaches 94oC. With
the machine power off, check the continuity
between P1-1 and P1-2 of the control board. If the
switch is OK, then the ohmmeter should read a
direct short. If not then it should read open.
§
If the switch is malfunctioning, replace it. Clean
the surface of the heat sink before installing the
switch.
·
Over Current. The fault light will be on continuously.
This indicates that the input current to the main
transformer has exceeded preset limits.
§
To check if the output is shorted, measure the
resistance by putting the ohmmeter leads (make
sure to disconnect HI Frequency leads):"+" of the
meter to Torch "+" output terminal and Work "-"
lead of the meter to the "-" output terminal.
Reading should be about 2 K Ohms. Reverse the
voltmeter leads, the resistance reading should be
less than 1.5 K Ohms.
If the resistance reading is different than above, check
the torch, the output bridge and Filter Board (PCB-5).
Troubleshooting
6-5