Tweco TD-750 Cutting Systems - Manual (Page 19)

Manual 0-2475 15 SERVICE
E. Merlin 3000 Cutting System - Start signal given to
Power Supply. Gas flows for selected pre-flow
time then 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 (Merlin 3000 Only)
a. Check for burnt or missing canted coil springs
inside the quick disconnect sockets.
6. Arcing between quick disconnect fittings (Merlin 3000
Only)
a. Remove the Torch Quick Disconnect Boot and
check for arcing between the quick disconnect
fittings. Repair as required.
F. TD-750 and Merlin 3000 Cutting Systems - Start
signal given to Power Supply. Gas flows for
selected pre-flow time then Pilot and DC LEDs
are ON steady. Pilot doesn't come ON and there is
no spark (no repetitive snapping sound) from the
spark gap in Arc Starter Box.
1. Defective Arc Starter PC Board, blown fuse, or faulty
connections in the 24 VAC circuit.
a. Refer to Section 4.04 Test Procedures to isolate
the defective assembly.
4.04 Test Procedures
This sub-section is divided into two paragraphs as fol-
lows:
A. Fault Isolation for TD-750 Cutting Systems
B. Fault Isolation for Merlin 3000 Cutting Systems
Depending on the type system installed refer to the ap-
propriate paragraph.
A. Fault Isolation for TD-750 Cutting Systems
WARNING
High voltage may be present in the Arc Starter
Box
The following procedure is to isolate the faulty assembly
to the Arc Starter PC Board, Power Base Unit, Torch, Torch
Leads, or Torch Leads Extension Assembly
1. To remove the voltage remove start signal from Con-
trol Module.
2. Place RUN/PURGE/SET in SET or PURGE position.
3. Control Module DC and PILOT LEDs are OFF.
4. Remove cover from Arc Starter Box.
5. On the Arc Starter PC Board measure for 24vac be-
tween J1-1 and J1-3. Later versions of the Arc Starter
PC Board have an LED indicator that is ON when the
24 vac is present.
• If 24 VAC is present, proceed to Step 15.
• If 24 VAC is not present, proceed to Step 6
NOTE
Connector J1 must be connected to the Arc Starter
PC Board.
6. Remove connector J1 from the Arc Starter PC Board
and reconnect making a good connection.
7. On the Arc Starter PC Board measure for 24vac be-
tween J1-1 and J1-3.
• If present proceed to Step 15.
• If not present proceed to Step 8
8. Remove connector J1 from the Arc Starter PC Board.
9. Measure for 24vac between J1-1 and J1-3 on the con-
nector.
• If 24vac is at the connector, Arc Starter PC Board is
defective.