Tweco 400 XT Ultra-Cut Plasma Cutting System - Manual (Page 164)

ULTRA-CUT 400 XT
A-5� APPENDIX Manual 0-5275
• The negative lead goes from the rear of the power supply to the remote arc starter or to the GCM 1000 XT in the case
of the AC 3000 XT.
o Cable pinched in or exiting the power track
o Short inside the Arc Starter such as a wire coming loose and grounding to the chassis.
o Short inside the torch mounting tube.
• Trouble shoot for external negative lead shorts by removing the lead from the rear of the power supply and try to start.
It won’t start but if you get the same 205 code the problem is inside the unit.
b. Short inside the supply:
• All the inverters outputs except that of IM1A are in parallel. If any inverter’s output is shorted it will appear as a short
across the power supply output.
Troubleshoot by removing all (or one at a time) of the inverter output connectors except those on IM1A. Then apply
Start to the unit. If it starts now one of the other inverters had shorted output. To find the defective one reconnect
one at a time until the fault reappears.
206 Not used. Reserved codes from the earlier product.
207 Unexpected Current in the Work Lead.
HCT1, a Hall Effect current sensor on the positive (work buss bar) measures the work lead current. Inverter section 1A is
enabled during preflow time but there should be no current in the work lead before the pilot is ignited and before the arc is
transferred to the work. If current greater than �A is detected before or during preflow something is wrong.
1. 207 code before START applied:
• Defective work current sensor, HCT1.
• Defective Relay PCB
• Defective CCM
Defective Sensor
• The work current sensor, HCT1, receives power, +15VDC and -15VDC from the Relay PCB. Both must be present for
the sensor to work properly. Measure between Relay PCB TP1 (or J1-�) to J1-1 for +15VDC and to J1-2 for -15VDC.
• If either + or – 15VDC not present remove the J1 connector and repeat the measurement at J1-1 & 2 on the Relay
board. If the voltage is now present the sensor is defective or shorted (the harness may be shorted). If voltages still
not present, the Relay board is defective.
Relay PCB
• Relay board LED D12, Work Current Detected, will light if the current sensor signal exceeds 0.05V. If D12 is on, mea-
sure the sensor output signal at J1-3 with signal common on J1-1. This signal should be 0V +/- 0.0�VDC. If greater
than +/- 0.0�VDC with no work lead current, the sensor is defective. If the signal voltage is within the limits and D12
is on, then the Relay board is defective.
• If D12 is not on and the 207 code is still active, either the Relay board or the CCM is defective.
CCM or ribbon cable
• The work current signal leaving the relay board is on the 40 pin ribbon cable (Relay J4 to CCM J23) pins 27 (-) & 28
(+). If the voltage here exceeds 0.1VDC with no work current the Relay board is likely defective. Another possibility
is in the �0 pin ribbon cable either pin 27 or 2� is shorted to an adjacent pin. Otherwise the CCM is defective.
2. 207 code after START applied (during preflow):
• Short between power supply negative output and Work circuit.
• Short between power supply negative output and earth ground.
• Defective or incorrectly installed user supplied equipment such as torch height controls that make connections to
power supply output.
Shorts are more likely to cause DC output voltage low (code 205). However, if the short has enough resistance it is possible
to show code 207. To test, remove negative output cable and reapply Start. If 207 code does not appear problem is a short
somewhere outside the power supply.