Thermadyne CE CutMaster 75, Service Manual

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SERVICE TROUBLESHOOTING 4-14 Manual 0-2869
4. Gate Drive & DC Sensing
a. After checking all previous steps in Subsection 4.10-
G, jumper TP1 to TP7 on the Logic PCB. Refer to
Appendix 3.
b. When the unit is turned on, the DC light should
remain ON.
c. Activate the torch. After two seconds INV ON
Indicator on the Logic PCB should come on and
remain on.
• If INV ON indicator does not remain on, re-
place Logic PCB.
• If INV ON indicator remains on, then check
for approximately 6 vdc between TP-1 to TP-4
and between TP-1 to TP-8 on the Logic PCB.
Refer to Appendix 3.
• If no voltage, replace Logic PC Board.
• If voltage is correct, measure for approxi-
mately 6 vdc between points as in the fol-
lowing chart:
E11 J2A E11 J2B
E19 J10A E19 J10B
IGBT A IGBT B
• If voltage is 0, replace Main PCB.
• If voltage is correct, proceed to the fol-
lowing step.
d. With jumper between TP1 to TP7 still in place, ac-
tivate the torch and measure for 250 vdc to 300
vdc between E61 (+) and E43 (-) on the Power
Output PCB. Refer to Appendix 11.
• If voltage is 0 vdc, replace IGBT Module.
e. With jumper between TP-1 and TP-7 still in place,
activate the torch and measure for approximately
250-300 vdc between J39-1 and J39-2.
• If voltage is 0 vdc, replace Output Power PCB.
• If voltage is correct, replace Logic PCB.
This completes the test procedures.