ESAB Powercut 875 Manuel D'instruction page 209

sectIon 5
c. the power light is on, but nothing happens when the torch switch is depressed. fault light does not
activate.
NOTE: Unplug high frequency connection before attempting to work on this problem.
1. Check the Pilot Arc fuse (F2) located on the rear panel. An open fuse will indicate a short in the torch. If the fuse is all
right, then check the following:
a. With the machine power on, depress the torch switch. On the control board the LED 1 should be lit as long as the
switch is depressed. If not then check:
i. Turn power off to the machine. Unplug Control board. Put an ohmmeter across P5-1 and P5-2 to take resis-
tance reading. Depress torch switch. Meter should read a short. If not, then one of the following is not work-
ing properly:
ii. Torch switch or the leads. Unplug the torch switch leads at the machine. Put a meter across the two plug
pins. Should read a short when the torch switch is depressed. If not, then either broken switch leads or mal-
functioning switch.
b. Check T2 transformer secondary voltages at the plugs P1 and P2. Refer to system schematic. Replace the trans-
former if the correct secondary voltages are not present.
c. If everything above checks out all right, then the PCB1 Control Board should be replaced.
d. fault light activates when torch switch is closed.
The Fault circuit is used to monitor conditions necessary for the safe operation of the PowerCut 875. The fault light
will glow amber under the following conditions and operations will come to a complete stop:
high/low line voltage. The Fault Light will rapidly blink on and off (5 times per second). This indicates that the in-
1.
put voltage is outside the "+" or "-" 15% safe operating range rating.
2. flow fault - The fault light will be mostly on but will blink off for 1/10th of a second every second. This indicates that
the air flow is low or there is no flow to the pressure switch.
a. Check the air pressure at the machine regulator. It should be adjusted to 65 psig. If no air pressure, check the air
at the supply point. Also, check for any obstructions in the air hose.
b. Air flow may be blocked at the torch tip. Check the torch consumables. Also check for any obstructions in the
torch leads.
NOTE: If above items check OK, the problem is internal. Send unit to an Authorized Repair Station for repair.
c. Put the 'Air Check' switch to On position. Air should flow through torch. To check if the pressure switch is open, put
voltmeter leads between P1-12 and P1-1. It should read about 5 VDC. When the pressure switch closes, the volt-
age will drop to zero volts.
d. Air Check switch may also be malfunctioning if the air is flowing continuously or if putting in the On position
does not turn air on.
over temperature. The fault light will be mostly off but will blink on for 1/10 of a second, every second. This gener-
3.
ally indicates that the duty cycle has been exceeded. Allow the power source to cool before returning to operate.
a. Thermal switch may be open. It will open if the temperature at the IGBT base reaches 94
power off, check the continuity between P1-1 and P1-2 of the control board. If the switch is OK, then the ohmme-
ter should read a direct short. If not then it should read open.
209
maIntenance
C. With the machine
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