Tweco 400 XT Ultra-Cut Plasma Cutting System With Automated Gas Control - Manual (Page 182)

ULTRA-CUT 400 XT
A-58 APPENDIX Manual 0-5306
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 40 pin ribbon cable either pin 27 or 28 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.
User Installed Equipment
For user installed equipment to cause 207 code it would have to be connected on the output (to the rear) of the current
sensors. To test, disconnect user equipment and apply CNC START. If code 207 is gone user equipment was defective or
connected incorrectly.
208 Unexpected current in Pilot Circuit
The Pilot board includes a current sensor to measure the pilot current. There should not be any pilot current until the invert-
ers and the pilot board are enabled and the arc starter has fired to ignite the pilot. Pilot current or the signal indicating pilot
current should not be present until the arc starter has fired.
Unwanted current signal due to defective sensor or defective circuit boards will most likely be present as soon as the power
up sequence completes and will be indicated as an active fault, E208. An actual short allowing real current to flow in the pilot
circuit will not occur until the inverter and pilot board are enabled near the end of preflow. This will result in the inverters
immediately being shut off and displaying a “last” or “latched” fault, L208. An LED, D2, on the Pilot board lights when the
Pilot Board is enabled.
1. 208 code before START applied:
• Defective Pilot board (current sensor circuit).
• Defective Relay PCB
• Defective CCM
Pilot PCB
Pilot current signal is on the 10 pin ribbon cable (Pilot J42, Relay PCB J3) between pins 8 (-) and 9 (+). With no current, the
signal should be zero +/- 0.05 V. Also the Relay board has an LED, D11, “Pilot Current Detected”, which will light if the pilot
current signal exceeds 0.15V. If the signal is not zero V.Pilot PCB is likely the cause. To be sure, disconnect the Pilot board
ribbon cable from the Relay board at J3. If D11 goes out, the Pilot board was the cause. Double check by measuring pin 8 &
9 again. If it’s zero V. now, the Pilot board is defective. If D11 is still on or pin 8 & 9 voltage still high check the Relay board.
Relay Board or CCM
If D11 on the Relay PCB is still on after the previous tests, measure the output to the CCM on the 40 pin ribbon cable (Relay
J4 to CCM J23) between pins 23 (-) and 25 (+). It should be less than 0.1V. If not, the Relay board is bad. If voltage is zero
then the CCM is defective.
2. 208 code comes on during preflow:
IM#1 and the Pilot board are enabled near the end of preflow. To have unwanted current there must be a path (short) for
current to flow between the inverter negative output (negative cable/torch electrode) and the Pilot return/tip before the arc
starter is enabled for pilot ignition.