Tweco TD-750 Cutting Systems - Manual (Page 17)

Manual 0-2475 13 SERVICE
SECTION 4:
CUSTOMER/OPERATOR
SERVICE
4.01 Introduction
This Section describes basic maintenance procedures per-
formable by operating personnel. No other adjustments
or repairs are to be attempted by other than Thermal
Dynamics Trained personnel.
WARNING
Disconnect primary power at the source before
opening the Arc Starter Box Assembly.
4.02 General Maintenance
The only routine maintenance required for the Arc Starter
Box is a thorough cleaning and inspection, with the fre-
quency depending on the usage and the operating envi-
ronment.
A. Cleaning
To clean the Arc Starter Box, first make sure that the
power is disconnected. Open the Arc Starter Box en-
closure and blow out any accumulated dirt and dust
with compressed air. The unit should also be wiped
clean. If necessary, solvents that are recommended
for cleaning electrical apparatus may be used.
While the enclosure is open, inspect the wiring in the
unit. Look for any frayed wires or loose connections
that should be corrected.
B. Checking Quick Disconnect Fittings
The fitting of the quick disconnect connectors can be-
come worn and cause improper cutting. Check the
fittings for any build up of material, worn o-rings,
damaged canted coil springs, etc. Replace any dam-
aged or worn parts as required.
4.03 Troubleshooting Guide
A. Troubleshooting
This Sub-Section covers troubleshooting that requires
disassembly and electronic measurements. It is helpful
for solving many of the common problems that can arise
with this torch assembly.
NOTE
Refer to Appendix I for the Interconnecting Dia-
gram of the Arc Starter Box.
B. How to use this Guide
The following information is a guide to help the Cus-
tomer/Operator determine the most likely causes for
various symptoms.
This guide is set up in the following manner:
X. Symptom (Bold Type)
Any Special Instructions (Text Type)
1. Cause (Italic Type)
a. Check/Remedy (Text Type)
Locate your symptom for the type cutting system, check
the causes (easiest listed first) then remedies. Repair as
needed being sure to verify that unit is fully operational
after any repairs.
A. TD-750 Cutting System - Start signal given to
Control Module. Gas flows for selected pre-flow
time then top Power Module DC LED and Control
Module PILOT LED flash momentarily. Control
Module DC LED is OFF, does not even come ON
momentarily.
1. Defective Pilot PCB or Power Module
In the Control Module check across W39 and W42
at the Pilot PCB. There should be a diode drop
across W39 to W42 in one direction and an open
in the other.
If shorted remove the wires at W39 and W42 at
the Pilot PCB and check again.
a. Replace Pilot PCB if shorted from W39 to W42
(with wires #39 and #42 removed).
b. Defective Power Module. Refer to the Control/
Power Components Operating Manual 0-2473
to test the output of the Power Module(s).
2. Defective Pilot PCB or Torch Components
In the Control Module check across W39A and
W48 at the Pilot PCB. There should be a diode
drop across W39A to W48 in one direction and an
open in the other.
If shorted disconnect the Umbilical Cable from the
front of the Control Module. and check again.
a. Replace Pilot PCB if shorted from W39A to W48
(with Umbilical Cable removed).