Tweco PCM - 102 Machine Torch - Manual (Page 37)

Manual 0-2818 5-5 SERVICE
5.06 Torch & Leads Troubleshooting
A. General Information
Failures in the Torch and Leads can be isolated to the Torch
Head or Torch Lead components. To properly isolate the
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 nega-
tive and positive charged sections of the torch. If the cen-
ter insulator does not provide adequate resistance, cur-
rent 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 resis-
tance 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 ohm-
meter.
The actual assembly and consumables may vary for dif-
ferent 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 sup-
ply 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 fit-
tings 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.