ESAB ESP-150 Manual De Instrucciones página 34

SECTION 5
b. Check voltage between each side of resistor R29 and the WORK output connection when MC is activated.
Place negative meter lead on side of resistor being checked and positive meter lead on the WORK output
connection. The voltage on one side should be the open circuit voltage (370 V). The voltage on other side
should be above 175 V. If lower voltage is under 175 V, PAC will drop out.
c. Check the resistance of R29. It should be 133 K ohm.
d. Disconnect R-29 resistor and measure the resistance from P1-1 to shunt (common). Resistance should be
200 K to 250 K ohms.
e. Check for continuity between R29 and electrode (-) torch connections.
f. With power off, mechanically pull in PAC. The resistance between POS and WORK connections should be
8 ohms.
8. Main arc fails to transfer to work.
a. Make sure that work clamp is securely fastened to the work piece.
b. Check for proper function of pilot arc and high frequency unit.
c. Check main disconnect switch and fuses.
d. Check main contactor (MC) by disconnecting primary power and check each contact for closure using an
ohmmeter while physically pulling contactor.
e. Check C24 and C24A capacitors (1900 uf, 450 V) with an ohmmeter. Resistance should be 900-1000 ohms
with capacitor connected in the circuit. If shorted, replace capacitor. Then check R18 resistor. The resistance
of R18 should be 5 ohms. The resistance between "DRB POS" and "CAP (+)" should be 25 ohms. If the stud
mounted rectifier on D/R board is shorted, the 25 ohm will be less than 5 ohms even when meter probes
are reversed.
f. Check open circuit voltage. It should be about 370 volts.
g. Check F1 and F2 fuses. The open circuit can still be 370 volts with one blown fuse.
h. Current control board (674935) may be defective.
9. Short tip life.
a. Check for correct gas pressure.
b. Check gas flow rate using flowmeter.
c. Check to see if pilot arc contactor (PAC) remains activated after main arc transfers. This can be done by
observing the spark in the spark gap of the high freq. unit. The high freq. spark should shut off as soon as
main arc starts. If spark continues after main arc is established, either main contactor (MC) or logic board
is defective.
d. Arc current is set too high.
e. Wrong cutting tip size. Use larger tip.
f. Defective current control board.
10. Pilot arc cycles on and off when torch switch is not depressed.
a. Unplug torch switch plug. If cycling stops, then torch switch wires or plug or torch switch itself are shorted.
b. Defective logic board.
11. No or limited control of output current.
a. Defective current control potentiometer (CCP). Check by placing negative meter lead on WORK output
connection and positive meter lead on current control board P1-2. (P1 is the larger of the two plugs.) With
the fan running (machine at idle), adjust CCP from min. to max. They read zero at min. (1.1 volts on ESP-
150); 10 Volts DC at max. The meter should move smoothly from zero to 10 V as CCP is rotated from min.
to max.
b. Defective logic board.
12. Gas does not shut off after 10 seconds of preflow.
a. Turn off ready-off switch (ROS). If gas continues to flow, solenoid valve is defective.
b. Defective logic board.
13. No arc.
Check that the mains power supply switch isturned on.Check that the welding current supply andreturn
cables are correctly connected.Check that the correct current value is set.
14. The welding current is interrupted during welding.
Check whether the thermal overload tripshave operated (indicated by the lamp on thefront panel).Check
the mains power supply fuses.
34
MAINTENANCE