Tweco XTTM-301 - Manual (Page 66)

SERVICE 5-12 Manual 0-4768
5.07 Torch And Leads Troubleshooting
A. General Information
Failures in the Torch and Leads can be isolated to the Torch Head or Torch Lead components. Isolating a failed part
requires the use of an ohmmeter and a Hi-Pot Tester.
WARNING
The use of a Hi-Pot Tester should be performed only by a qualified electronic technician.
In the Torch Head the center insulator separates the negative and positive charged sections of the torch. If the center
insulator does not provide adequate resistance, current which is intended for the pilot arc may be dissipated into the
torch head, resulting in torch failure.
In the Torch Leads the negative and positive leads are isolated from each other. If there is not adequate resistance
between the leads then torch failure may occur.
B. Quick Check Procedure
This quick check will identify major isolation failures in the Torch Head or Torch Lead components using an ohmmeter.
The actual assembly and consumables may vary for different torches but the basic procedure is the same for all torches.
Make the quick check on the Torch Head and Leads as follows:
WARNINGS
Disconnect primary power to the system before disassembling the torch or torch leads.
DO NOT touch any internal torch parts while the AC indicator light of the Power Supply is ON.
1. Remove the consumables from the torch.
2. Disconnect the torch leads from the power supply to isolate the torch from power supply circuits.
3. Using an ohmmeter (set to 10K or higher), check for continuity between the positive and negative torch fittings.
• If there is continuity between the two torch fittings proceed to Step 4.
• If no continuity (infinite resistance) is found between the two torch fittings proceed to paragraph C.
4. Remove the torch head from the leads (refer to the proper Section on servicing the Torch Components).
5. With the torch head disconnected from the leads, measure the resistance between negative fitting or cathode
body of the torch head and the positive fitting or anode body of the torch head.
No continuity (infinite resistance) should be measured between negative and positive sections of the torch
head.
• If there is continuity, torch head must be replaced.
• If no continuity (infinite resistance) is found proceed to Step 6.