Tweco TD-750 Cutting Systems - Manual (Page 18)

SERVICE 14 Manual 0-2475
b. Defective Torch Components (Torch, Torch
Leads, Torch Leads Extension Assembly or Arc
Starter Box) proceed to possible cause #3 to iso-
late possible defective component.
3. Defective Torch, Torch Leads, Torch Leads Extension
Assembly or Arc Starter Box
Reconnect the Umbilical Cable to the front of the
Control Module. 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 remove the Torch Leads from the out-
put of Arc Starter Box and check again.
a. If no longer shorted Torch or Torch Leads are
defective. Refer to Torch Instruction Manual
0-2476.
b. If short remains disconnect Torch Leads Exten-
sion Assembly from input of Arc Starter Box
and check again.
c. If no longer shorted Arc Starter Box Assembly
is defective. Proceed to possible cause #4 to
isolate problem in Arc Starter Box.
d. If short remains disconnect Torch Leads Exten-
sion Assembly from front of the Power Base
Unit and check again.
e. If short remains the Torch Leads Extension As-
sembly, Umbilical Cable, or torch quick discon-
nects in the Power Base Unit are shorted.
4. Defective Arc Starter Box
Inside the Arc Starter Box remove the wire from
either E1 or E2 on Arc Starter PC Board. Make an
ohms check across E1 to E2.
a. If shorted, replace defective Arc Starter PC
Board.
b. If not shorted the problem is in the input or
output quick disconnects on the Arc Starter Box.
Repair as needed.
B. 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 DC and PILOT LEDs are ON steady. No
spark at spark gap in Arc Starter Box.
1. Bad Connection in Arc Starter Box
a. Connection at J1 on the Arc Starter PC Board is
bad. Check connection by removing and rein-
stalling the plug.
2. Arc Starter PC Board, Power Base Unit, Torch, Torch
Leads, or Torch Leads Extension Assembly defective
a. Refer to Section 4.04 Test Procedures to isolate
the defective assembly.
C. TD-750 Cutting System - Start signal given to
Control Module. Gas flows for selected pre-flow
time then Control Module Pilot and DC LEDs are
ON steady. Pilot doesn't come ON but there is a
spark (repetitive snapping sound) from the spark
gap in Arc Starter Box.
For the spark gap to fire, the Power Supply DC out-
put has to be getting to the Arc Starter Box.
1. Consumable Torch parts are shorted
a. Check or replace the consumable Torch parts
2. Arcing or burning inside Torch Head Assembly
a. Remove the consumables from the Torch Head
Assembly and check for signs of arcing or burn-
ing inside the torch head. Replace Torch Head
Assembly if required.
3. Arcing or burning between the Torch fittings or from
the fittings to the Mounting Tube
a. Remove the Torch Head Assembly from the
mounting tube and check for arcing or burning
between the fittings or from the fittings to the
tube. Repair as required.
4. Defective CD transformer
a. Check for arcing around the CD Transformer
(while spark gap is firing) and look for any
cracks in the ferrite cores. If either problem
exists replace the CD Transformer.
5. Defective canted coil springs
a. Check for burnt or missing canted coil springs
inside the quick disconnect sockets.
6. Arcing between quick disconnect fittings
a. Remove the Torch Quick Disconnect Boot and
check for arcing between the quick disconnect
fittings. Repair as required.
D. Merlin 3000 Cutting System - Start signal given to
the Power Supply. Gas flows for selected pre-
flow time then Pilot LED flashes momentarily.
DC LED is OFF, does not even come ON momen-
tarily.
1. Problem not in the Arc Starter Box. The Power Supply
is has no DC voltage output.
a. Refer to the Power Supply Service Manual
0-2569 to test the output of the Power Supply