Tweco Troubleshooting Power Supply - Manual (Page 27)

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as I_REF. I_REF is sent to the inverter module(s) on CN6-2 (16 ckt ribbon
cable).
I_REF should be 80% of Cut Demand if unit is 100, 200 or 300A. If unit is 150A,
I_REF is 60% of Cut Demand .
For example, 150A power supply set for 100A out. Initial cut demand should
1.7V, I_REF at CN6-2 should be 1.7 * 0.6 =1V. If it had been a 100A unit set
for 100A Cut Demand would be 2.6V and I_REF should be 2.6 * 0.8 = 2.1V.
If this is not correct PCB5 is defective.
Inverter
If I_REF as measured above is correct, the inverter may be faulty causing the
2-6 code.
Signal /OCR is applied in parallel from each inverter on CN6-12 (TP0
common). If an actual over current occurred the inverter latches this line low
until power is recycled. If, while cutting, this line went low for some other
reason, even momentarily, the CCM will stop the cut and latch the 2-6 code even
if the OCR line went back high. To see if this is the case, momentarily apply
CNC START just long enough to start preflow then remove it. This will allow the
CCM to unlatch the code.
If momentarily applying START does remove the code, possible causes in the
inverter are the ribbon cable not locked into its connector either on PCB5 or one
of the inverters. Also loose connection on one of the following connectors in the
inverter:
Connectors that could be involved are CN1, CN2 CN33, on PCB13; CN3, CN5,
CN7, CN33 on PCB1; CN1, CN4, CN5 on PCB12. If cannot be resolved replace the
inverter.
If momentarily applying START does not remove the 2-6 code then one of the
inverters may be have latched the /OCR line (CN6-12) low. If this line is not low
then go to section on PCB5 & CCM.
If CN6-12 is low and there is more than one inverter module, you have to
determine which one has set the /OCR signal. Because each inverter is connected
in parallel to the ribbon cable’s /OCR line, the only way to tell which one is
holding the line low is to disconnect them one at a time. Because the /OCR is
reset when power is removed, the ribbon cable (CN6 on each inverter) must be
disconnected with power on. Be very careful!
If the first one removed is not the cause, plug it back in otherwise when the
last one is removed you will set code 2-4, Power Supply Not Ready. It takes a
couple seconds for the CCM to recognize the fault is removed and clear the fault
so after removing each CN6 give it enough time to clear before deciding if you
found the bad one.
If none of the inverters appear to holding the CN6-12 low then the ribbon
cable nay be shorted.
PCB5 /OCR
Having determined above that CN6-12 (TP0 common) is high but 2-6 code
remains after momentarily applying START then either PCB5 or CCM is