ESAB POWERCUT-1500 Bedienungsanleitungen Seite 188

SECTION 5
c. To check if the output is shorted, measure the resistance by
putting the ohmmeter leads across the output. Put the black lead
to the "work" terminal and the red lead to the torch electrode
terminal. The reading should be about 2K OHMs.
b. If the resistance reading is different than above, check the torch,
the output bridge and Start-up Board (PCB-6).
E. Air is On but nothing happens when torch switch is operated.
1. Check the torch. Make sure that the valve pin is installed and the heat
shield is very tight.
2. Check to assure high frequency is present at the torch. Disconnect
HI FREQUENCY leads. Check for 575 volt supply to the high
frequency unit between P2A-1 & P2A-3 of the High Frequency Board
(PCB2) with torch switch closed.
3. With HI FREQUENCY leads disconnected, measure open circuit
voltage. It should be 320 VDC between "Work" and "Torch" terminals.
If it is not present then any one of the following may not be working
properly:
a. Check the operation of the Thermal Switch (TS1). See D.3.a.
above.
b. Check Air Check switch operation. It might be stuck in On
position. Pilot arc will not initiate if this switch is in the ON position.
(safety reasons)
c. Check air flow switch. There may be internal short. See D.2.c
above.
d. Measure voltage across C5 or C6 capacitor. It should be as
follows:
approx. 325 VDC with 230 V supplied to the 230/460 volt unit.
approx. 294 VDC with 208 V supplied to the 230/460 volt unit
approx. 325 VDC with 460 V supplied to the 230/460 volt unit
approx. 400 VDC with 575 V supplied to the 575 volt unit
If not, one of following could be malfunctioning:
1). Check the capacitors C5 and C6 for any damage.
2.) Check input bridge/SCR Module (BR1) This can be
checked without taking it out of the circuit using an volt/
ohmeter. Replace it if found malfunctioning. Follow bridge
installation instructions.
3.) Check Inrush current resistor (R1), located on the Input
Bridge
malfunctioning.
e. IGBTs may be damaged. See IGBT installation procedure. Before
replacing IGBTs, make sure to check the zener diodes and pico
fuses on the IGBT driver boards.
166
TROUBLESHOOTING
Heatsink and SCR (Q1). Replace if