MAINTENANCE
3-28 powermax1250 Service Manual
4
Test 7 – torch stuck open (TSO)
• Check the resistance between the pilot arc IGBT (Q8) and J17. The value should be less than (<) 100Ω.
• Switch to gas test mode and check the resistance again. The value should be greater than (>) 1kΩ.
• If the value is less than (<) 100Ω all the time, check the resistance between the pilot arc IGBT (Q8) and J17
with the torch removed. If the value is less than (<) 100kΩ, replace the pilot arc IGBT (Q8).
• If the resistance is always greater than (>) 100Ω, then the electrode/nozzle circuit is open.
– Inspect the wiring to the torch.
– Replace all consumables and verify that the torch will fire.
Note: The retaining cap should be snug, but not over-tightened.
– If the torch plunger does not move freely in the torch head, replace the torch head.
• Verify that the pilot arc IGBT (Q8) is open by placing a jumper wire between J14 and the pilot arc IGBT
(Q8). Then attempt to fire the torch. If the torch fires, replace the pilot arc IGBT (Q8).
Note: All values are ±25%.
Pilot arc IGBT
Q8
J17
J14
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