Hypertherm HT4001 Plasma Arc Cutting System - Manual (Page 144)

MAINTENANCE
3-98
6-18
HT4001
Instruction Manual
Problem Possible Causes and Solutions
13. The POWER DC indicator
illuminates, and there is
high frequency, but there is
no pilot arc.
13.1. Pilot arc relay CR1 is not closing (not getting 120VAC from relay
board PCB4).
See if the CR1 relay contacts close after the START command
is given. (See Figure 7-3 for location of CR1) If CR1 does not
close:
• With an AC voltmeter across the relay, see if 120VAC is
coming from PCB4 after START command is given.
• If there is no 120VAC, check connectors, terminals, pins, and
associated wiring to PCB4.
• If wiring is OK, there may be a problem with PCB4 or control
board PCB2.
13.2. Pilot arc relay CR1 is defective.
If there is 120VAC across the relay (see above steps), and CR1
does not close, replace CR1.
13.3. Main contactor (CON1) or PCB4 is defective.
• With an AC voltmeter, see if contactor CON1 is getting
120VAC after START command is given. (The contactor
should make a loud clicking sound if it is getting the 120VAC.
See Figure 7-7 for location of CON1)
If there is no 120VAC, check pins, connectors and associated
wiring from CON1 to PCB4.
• If wiring is OK, PCB4 or PCB2 may be defective.
• If CON1 is getting 120VAC from PCB4 as described above,
measure the voltage between all secondary terminals of main
transformer T2 going to choppers CH1-CH4 after the START
command is given (See sheet 3 of 13 in the wiring diagrams).
The voltage between any two of the three points for each
chopper should be equal to 200VAC.
If there is no voltage at any of the above points, replace CON1.
If there is voltage at some but not all of the above points, check wiring
and connections to and from T2. If wiring checks out OK, return to
Initial Checks section and repeat steps 1-5.