Tweco Troubleshooting Power Supply - Manual (Page 24)

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Code 2-5 remains set (latched) after Start is removed to indicate why unit
stopped. Code is cleared next time Start is applied (if fault has been removed) or
when power is turned off.
Causes for 2-5 code set before pilot ignition:
• J6 on CCM not connected (CCM connection to DC Output Voltage) or
open connection.
• CN1 & CN14 reversed on PCB5
• Shorted Pilot Regulator (chopper).
• Inverter not getting Start signals (START & START2) from CCM.
• Inverter defective.
Causes for 2-5 code set during pilot or cut:
• No or low Preflow or Plasma gas flow.
J6 connection open
The connection from J6-8 to the Work busbar has a small inductor spliced into
the wire. If this inductor is open CCM will not detect output voltage. Check
continuity from J6-8 to Work busbar, should be less than 100 ohms.
Test for shorted chopper.
• First turn off input power and jumper across diode D2 (mounted on the
chassis to the rear of the chopper). Leave jumper on for a couple minutes
to insure chopper capacitors bleed down to zero volts.
• Chopper freewheel diodes. Measure resistance between TB2 and TB4 on
chopper. Expect to see over 20K ohms with it slowly increasing as it
charges a capacitor. If using a meter with a diode scale expect to see
continuity one way (diode forward biased) and open with probes reversed.
A low resistance with either method indicates a short.
• Chopper IGBTs. Measure resistance TB1 to TB4 on chopper. Should be
open circuit. . If using a meter with a diode scale expect to see continuity
one way (diode forward biased) and open with probes reversed. A low
resistance with either method indicates a short.
Inverter Start signals
CCM has redundant start signals, START, CCM J35-7 (26 ckt ribbon), and
START2, CCM J35-6, to insure start can be removed in case of a fault in one of
the start circuits. The signal START2, should be present, active low, anytime
CNC START is applied. If there is a fault, such as low DC Voltage, START is
immediately removed. We know CNC START is getting to CCM else code 2-5
wouldn’t be set.
Measure START2. Apply CNC START (J15-3 & 4 or jumper TB1-5 & 6) and
measure for low on J35-7 (CCM TP1 common). If high, about +10 VDC, CCM is
defective.
Measure START. Apply CNC START (J15-3 & 4 or jumper TB1-5 & 6) and
measure for a momentary low on J35-6 (CCM TP1 common). This may be