Tweco PCM-120 Machine Torch - Manual (Page 39)

Manual 0-2698 5-9 CUSTOMER/OPERATOR SERVICE
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 para-
graph C.
4. Remove the torch head from the leads (refer to
the proper Section on servicing the Torch Com-
ponents).
5. With the torch head disconnected from the leads,
measure the resistance between negative fitting
or cathode body of the torch head and the posi-
tive fitting or anode body of the torch head.
No continuity (infinite resistance) should be mea-
sured between negative and positive sections of
the torch head.
• If there is continuity, torch head must be re-
placed.
• If no continuity (infinite resistance) is found
proceed to Step 6.
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 re-
placed.
• 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 fur-
ther 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 quali-
fied electronic technician.
1. To test the Torch Head center insulator for insula-
tion breakdown use the following procedure:
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 cur-
rent 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 posi-
tive 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 cur-
rent 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 pro-
ceed to Step 3.