Tweco XTTM-301 - Manual (Page 67)

Manual 0-4768 5-13 SERVICE
6. Check the torch leads by measuring the resistance between the positive pilot lead connector and the negative
lead fitting.
• If there is continuity, torch leads must be replaced.
• If no continuity (infinite resistance) is found proceed to paragraph ‘C’ (see NOTE).
NOTE
It is possible that the Torch Head and Torch Leads will test properly with an ohmmeter. The Torch Head and Torch
Leads should be tested further for insulation breakdown if no other fault can be found.
C. Checking Proper Isolation Resistance Procedure
The Torch Head and Torch Leads should be tested further for insulation breakdown if no other fault has been found.
This procedure requires the use of a Hi-Pot Tester.
WARNING
This procedure should be performed only by a qualified electronic technician.
1. Test the Torch Head center insulator for insulation breakdown as follows:
a. Remove the Torch Head Assembly from the Torch Leads if not already done.
b. Remove the consumables from the Torch Head Assembly if not already done.
c. Connect a Hi-Pot Tester capable of producing 2500 VAC between the positive pilot lead and the negative
lead fittings.
d. Increase the output of the Hi-Pot Tester to a maximum of 2500 VAC.
• If the voltage drops to 0 VAC or leakage current is detected, then the Torch Head center insulator is breaking
down and the Torch Head must be replaced.
• If the Torch Head center insulator passes the test, then proceed to Step 2.
2. To test the Torch Leads for insulation breakdown use the following procedure:
a. Connect the Hi-Pot Tester between the positive pilot lead and the negative lead fittings. The fitting on the
other end of the Torch Leads must be separated (isolated) from each other.
b. Increase the output of the Hi-Pot Tester to a maximum of 2500 VAC.
• If the voltage drops to 0 VAC or leakage current is detected, then the insulation between the Torch Leads
is breaking down and the Torch Leads must be replaced.
• If the Torch Leads passes the test, then proceed to Step 3.
3. Visually check that the torch switch wires, pilot lead connection, and negative lead connections are properly
connected and in good condition (no shorts or arcing).
• If problems are evident, repair or replace as required.
• If there are no visual problems, then proceed to Step 4.