Thermadyne CE CutMaster 75, Service Manual

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Manual 0-2869 4-13 SERVICE TROUBLESHOOTING
Art # A-03212
L1 L2 L3 L4
T1
T2
T3
T4
#13
#12
#78
L1
L2
Input
Side
#5
#4
#3
#2
#1
208/230-V Main Input Contactor
2. Check for 28 VAC at J23-1 to J23-3 on the Main PC
Board.
a. If greater than 30 VAC, input line power is too
high.
b. If there is no AC power, check the fuse. If the
fuse is ok, the auxiliary transformer is faulty.
Replace the Main PC Board.
E. Gas Solenoid Circuit Test
Make the following voltage checks and replace the faulty
part as required.
1. Place the RUN/SET Switch to the SET position.
2. Measure for 28 VAC across Solenoid wires #8 and
#9. Refer to System Schematic in Appendix Sec-
tion.
• If 28 VAC is present, replace Solenoid/Pressure
Switch Assembly.
• If 28 VAC is not present, check for 70 psi (4.8
bar) at the pressure regulator.
3. Check for less than 2 vdc at P1-14 to TP1 on Logic
Board.
• If less than 2 vdc, replace Main PC Board.
• If more than 2 vdc, replace Logic PC Board.
F. Output Power Tests
1. No DC Output
Activate the torch.
• If INV ON indicator D21 on Logic PC Board does
not turn ON, then replace the Logic PCB.
• If the INV ON indicator D21 blinks ON then OFF
immediately, perform the following test:
a. Disconnect J28 from the CD PC Board to dis-
able the CD signal.
WARNING
Connector J28 on the CD PC Board must be dis-
connected to prevent electrical damage to measur-
ing equipment when testing the open circuit volt-
age (OCV).
b. Activate the torch. Logic PC Board Inverter
ON Indicator, D21, turns ON.
c. Measure open circuit voltage between E61(+)
to E43(-) on the Power Output PC Board. Volt-
age should be 200-300 Volts. If voltage is less
than 10 V, each
IGBT Module and Output Di-
ode Module should be tested individually.
WARNING
The following tests must be performed with the
power supply connected to primary input power.
There are extremely dangerous voltage and power
levels present inside this unit. Do not attempt to
diagnose or repair without proper training in power
electronics measurement and troubleshooting tech-
niques.
c. Activate the torch.
• After 2 seconds D21 on the Logic PCB should
turn ON. If D21 does not turn ON, replace
Logic PCB.
d. Measure open circuit voltage between E61(+) to
E43 (-) at the Output Power PC Board. Voltage
should be greater than 200 V. If voltage is less than
10 V, refer to the output diode test measurements
or IGBT module test measurements or shorted
torch measurements.