Thermadyne CE CutMaster 75, Service Manual

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SERVICE TROUBLESHOOTING 4-8 Manual 0-2869
c. Measure across pins J41-1 and J41-3 on Power
Output PC Board.
• If less than 2K ohms, replace Power Output
PC Board.
• If more than 2K ohms, replace Logic PC
Board.
d. Check for damaged torch leads. If pilot wire
arcs to torch switch PIP lead it can damage PCB
and the torch leads.
J41-1
A-03173
J41-3
Power Output PC Board
Output Diode A
4.08 Pilot Arc Problems
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.
Locate your symptom below:
A. No gas flow; AC indicator ON; TEMP indicator
off; GAS and DC indicators OFF (Torch Switch,
CNC Control Switch or Pendant Control switch
must be pressed)
1. Faulty torch or leads
a. Test per Torch Instruction Manual.
2. Faulty Output Power PC Board
a. With ON/OFF switch in the OFF position, dis-
connect J39 from the Output Power PCB. Acti-
vate the torch and check for continuity between
J39-6 and J39-7 on Output Power PCB.
• If no continuity is found, check for continu-
ity between J41-1 and J41-3. If continuity is
found, replace the Power Output PCB.
• If no continuity, check the torch connection.
If torch connection is okay, replace the torch.
J39-6
Power Output PC Board
J39-7
A-03266
Output Diode B
3. Faulty Logic PCB
a. With torch activated, check indicator D20 on
the Logic PCB. Replace Logic PCB if D20 is on.
B. Gas flows; small arc may be visible in torch; AC
indicator ON; TEMP indicator off; GAS indicator
ON; DC indicator off or blinks on/off once.
1. Faulty torch
a. Disconnect and isolate the Pilot return wire
from the Power Supply. Activate the torch and
observe the front panel DC LED.
• If the DC indicator comes on and remains
on, replace the torch.
2. Faulty IGBT or Output Diode Module Assembly(s)
a. Check per Subsection 4.10-C; repair as needed.
3. Faulty Main PCB
a. Test per Subsection 4.10-F; repair as needed.