Thermadyne CE CutMaster 75, Service Manual

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Manual 0-2869 4-5 SERVICE TROUBLESHOOTING
E. Main Arc Test
Make sure the work cable is firmly connected to the work-
piece. Activate the torch (press torch switch on the handle,
send START signal from CNC Control or press the torch
switch on the Remote Pendant) to establish a pilot arc.
Bring the torch to within 1/8"-3/8" (3-10 mm) of the work-
piece to establish the main cutting arc, and note the fol-
lowing:
• Main cutting arc starts
• Pilot Control Relay (PCR) opens
This completes the Main Arc Test. If the above are all
correct then the equipment should be operating properly.
If problems still persist then contact Technical Services.
If the torch does not function as noted then note the symp-
tom and proceed to Subsection 4.09, Main Arc Problems.
4.07 Main Input and Internal Power
Problems
A. Opening Power Supply Enclosure
The cover of the Power Supply must be removed for ac-
cess to input power connections and test points.
WARNING
Disconnect primary power at the source before as-
sembling or disassembling the Power Supply, torch
parts, or torch and leads assemblies.
1. Remove the upper screws securing the cover to the
main assembly.
2. Loosen, but do not remove, the lower screws.
NOTE
There is a ground wire attached from the cover to
the main body of the unit.
3. Carefully lift the cover off the unit, and remove the
nut securing the ground wire to the side panel.
4. Re-install the cover by reversing the above steps.
A-03001
Lower
screws
Upper screws
Ground wire
Lower
screws
Upper
screws
Cover Removal
Locate your symptom below:
A. Main power line fuses blow as soon as main
disconnect is closed
1. Input power cable installed incorrectly or defective
power cord.
a. Refer to Subsection 5.07-E, Input Power Cable
Replacement procedures, and check that the in-
put power cable is not defective or installed
incorrectly. Section 4.10-D illustrates wiring
connections.
B. Main power line fuses blow immediately after the
ON/OFF Switch is turned on.
1. Faulty Input Diode
a. Test Input Diode per Subsection 4.10-C; repair
as necessary.
C. Fan does not operate; AC indicator on front panel
of power supply is OFF
1. Front Panel ON/OFF switch in OFF position
a. Place switch to ON (up) position.