Thermal Dynamics CUTMASTER 60i Service Manual page 61

9. Poor cut quality, short tip life, especially at higher current setting.
May be caused by a shorted pilot IGBT.
a. With shorted pilot SW total output current doesn't change but some of the total will flow through the
shorted SW instead of cutting the metal and increases the tip wear. At lower current setting may have
difficulty transferring or keeping the arc on. Moving the torch away from the work will go immediately
to pilot as though it was in the RAR mode. This should have been found in the resistance tests. Go to the
first section, Resistance & Diode Tests #7.
10. Pilot, But No Arc Transfer.
There is a current sensor (U610) in the work lead circuit on the Inverter board. When the pilot is close enough
to the work some current will flow into the work lead. When the current reaches about 5A, as sensed by U610,
the pilot switch is shut off and transfer is completed. At the same time the current, 25A when piloting, changing
to the output current setting between 10 and 60A and the OK to Move relay is energized as indicated by the OK
to MOVE LED (D642) on the Inverter board. Failure to transfer may be caused by:
a. Work lead not connected or not making good electrical connection to either the plasma supply or the
work piece.
b. U610 on the inverter board defective not sensing the work current. With a DC Ammeter measure the
work current while trying to transfer. If at least 5A and the OK to Move LED does not light (refer to #10
for OK to Move) replace the Inverter board.
11. No OK to Move.
OK to Move, is a relay on the Inverter board. It is only needed for automation units where its contacts, rated for
24 VAC/DC, @ 1A, are connected to the rear panel CNC connector. However it is activated in all units when
work lead current exceeds 5A. (Refer to #9). There is an LED, OK to MOVE, (D642) that turns on when its relay
coil is energized and can be used to indicate arc transfer.
a. OK to MOVE LED on but no contact closure at the CNC connector J1-12 & 14. The OK to Move contacts
connect through J609-12 & 14 and pass directly through the Automation Interface board to the CNC
connector J1 on pins 12 & 14. Check for continuity from J1 through the board and harness to J609. If OK
replace the Inverter board.
b. If the OK to Move LED on the Inverter board does not come on and you do clearly have arc transfer, are
cutting metal, for the OK to Move signal on J609-11 (+) to J609-10 (common, work lead). If it is low, less
than 2 volts, replace the Inverter board.
c. If J609-11 is high, the problem could be either the Control & Display board or the Inverter board.
12. End of Life Indicator (EOL)
Circuits measure the electrode to tip voltage. If while cutting the voltage exceeds what is normal it indicates the
electrode or possibly the tip has reached the end of its life and the EOL indicator blinks to indicate this. It does
not prevent continuing to cut. Note that the EOL is inactive during drag cutting and at currents below 20A.
a. Replace the tip and electrode and recycle the power. If EOL still blinks with a new tip and electrode the
pilot switch may be shorted. Refer back to #8 in this section and also #7 in the first section, Resistance &
Diode Tests.
b. An error measuring tip volts could also be the cause. Perform the test in Fault Code Section #6, E012,
Output Fault, step c.
Manual 0-5475 SERVICE
CUTMASTER 60i
5-27